Biogenic Synthesized Ag/Au Nanoparticles: Production, Characterization, and Applications

Nelson Duran and Amedea B. Seabra
Publicado por Current Nanoscience, 11/2017

Background: Bimetallic silver-gold nanoparticles (Ag/Au NPs) with different structures have recently gained scientific attention due to their new and superior properties in comparison with metallic NPs made from a single metal. Ag/Au NPs (alloy or core-shell structures) have been applied to several biomedical, technological, and environmental applications. The potential applications of Ag/Au NPs are widespread yet poorly investigated in comparison with monometallic NPs. Besides traditional chemical and physical routes to synthesize bimetallic Ag/Au NPs, biogenic protocols are considered cost-effective, simple, and environmentally friendly. Despite their simplicity, biogenic routes to synthesize Ag/Au NPs are less explored than traditional synthetic protocols. Methods: In this context, we present a review and discuss recent progress in the preparation of bimetallic Ag/Au NPs with different morphologies, structures, and size distributions using biogenic synthetic protocols. Results: Biogenic synthesis using plant extracts, algae, bacteria, fungi, and other biological agents are presented and discussed. The characterization and potential applications of biogenically synthesized Ag/Au NPs in the different areas of medicine and biological applications, such as antibacterial, anticandidal, anticancer, antidiabetes, and as sensors for clinical diagnosis are presented and discussed. Conclusion: Finally, challenges and drawbacks in the biological routes for the preparation of Ag/Au NPs for industrial applications are also discussed.


F. Côa, Z. Clemente, M. Strauss, L.L. Rodrigues Neto, J.R. Lopes, R.S. Alencar, A.G.S. Filho, O.L. Alves, V.L. Castro and E. Barbieri
Publicado por Science of the Total Environment, 07/2017

In this work, industrial grade multi-walled carbon nanotubes (MWCNT) were coated with humic acid (HA) for the first time by means of a milling process, which can be considered an eco-friendly mechanochemical method to prepare materials and composites. The HA-MWCNT hybrid material was characterized by atomic force microscopy (AFM), scanning electron microscopies (SEM and STEM), X-ray photoelectron spectroscopy (XPS), termogravimetric analysis (TGA), and Raman spectroscopy. STEM and AFM images demonstrated that the MWCNTs were efficiently coated by the humic acid, thus leading to an increase of 20% in the oxygen content at the nanotube surface as observed by the XPS data. After the milling process, the carbon nanotubes were shortened as unveiled by SEM images and the values of ID/IG intensity ratio increased due to shortening of the nanotubes and increasing in the number defects at the graphitic structure of carbon nanotubes walls. The analysis of TGA data showed that the quantity of the organic matter of HA on the nanotube surface was 25%. The HA coating was responsible to favor the dispersion of MWCNTs in ultrapure water (i.e. -42mV, zeta-potential value) and to improve their capacity for copper removal. HA-MWCNTs hybrid material adsorbed 2.5 times more Cu(II) ions than oxidized MWCNTs with HNO3, thus evidencing that it is a very efficient adsorbent material for removing copper ions from reconstituted water. The HA-MWCNTs hybrid material did not show acute ecotoxicity to the tested aquatic model organisms (Hydra attenuata, Daphnia magna, and Danio rerio embryos) up to the highest concentration evaluated (10mgL-1). The results allowed concluding that the mechanochemical method is effective to coat carbon nanotubes with humic acid, thus generating a functional hybrid material with low aquatic toxicity and great potential to be applied in environmental nanotechnologies such as the removal of heavy metal ions from water.


D. Ballottin, S. Fulaz, F. Cabrini, J. Tsukamoto, N. Durán, O.L. Alves and L. Tasic
Publicado por Materials Science & Engineering B: Solid-State Materials for Advanced Technology, 06/2017

This paper introduces cotton fibers impregnated with biogenic silver nanoparticles (AgNPs), synthesized from a Fusarium oxysporum fungal filtrate (FF) solution, and open up the possibility for their use in medical environment and agriculture clothing as means to avoid microbial spreading. After thorough AgNPs characterization, regarding their physical, chemical and biochemical properties, Minimum Inhibitory Concentrations (MIC) against some human and orange tree pathogens were determined. We report the strong AgNPs activity against Candida parapsilosis and Xanthomonas axonopodis pv. Citri (Xac) that was morphologically characterized, pointing to strong AgNPs effects on microorganisms membranes. Cotton fibers were then impregnated with AgNPs suspension and these maintained strong antimicrobial activity even after repeated mechanical washing cycles (up to 10). Reported data might point to an application for biogenic AgNPs as potent agrochemicals, as well as, to their application in textiles for antiseptic clothing for medical and agronomic applications.


A.F. de Faria, A.C.M. de Moraes, P.F. Andrade, D.S. Silva, M.C. Gonçalves and O.L. Alves
Publicado por Cellulose, 02/2017

Bacterial adhesion and consequent biofilm formation are one the biggest hurdles in membrane-based technologies. Due to numerous problems associated with bacterial colonization on membrane surfaces, the development of new approaches to prevent microbial growth has been encouraged. Graphene oxide, produced by the chemical exfoliation of graphite, is a highly water-dispersible nanomaterial which has been used as a platform for the anchoring of nanoparticles and bioactive molecules. In this present study, we propose the fabrication of antimicrobial membranes through the incorporation of graphene oxide-silver nanocomposites into a cellulose acetate polymeric matrix. Transmission electron microscopy, Raman, and UV–visible diffuse reflectance spectroscopy measurements confirmed the presence of graphene oxide-silver sheets in the modified membranes. In comparison to pristine membranes, membranes containing graphene oxide-silver nanocomposites showed larger surface pores and increased pure water flux. In addition, membranes embedded with graphene oxide-silver presented strong antibacterial activity, being able to inactivate adhered bacteria at a rate of 90% compared to pristine cellulose acetate membranes. Our results strongly suggest that the incorporation of graphene oxide-silver nanocomposites to cellulose acetate is a promising strategy to produce membranes that are able to minimize bacterial attachment and growth.

DOI: 10.1007/s10570-016-1140-6


D.T. Castro, M.L. Valente, C.Aires, O.L. Alves and A.C. dos R
Publicado por Gerodontology, 09/2017

This study evaluated the release of ions and the cytotoxicity of acrylic resins incorporated with silver vanadate decorated with silver nanoparticles (AgVO3).
The inhibition of the accumulation of microorganisms on the resins is critical in preventing diseases. However, the hypothesis is that the release of ions from the incorporation of AgVO3 may be important in biocompatibility.
Specimens of autopolymerising (AP) and heat-polymerising resin (HP) with AgVO3 were prepared and immersed in culture medium. The release of silver ions (Ag) and vanadium (V) was evaluated by mass spectrometry with inductively coupled plasma (ICP-MS) (n=9) and the cell viability of fibroblasts L929 by MTT (3-[4,5-dimethylthiazol- 2yl]-2,5-diphenyltetrazolium bromide) (n=12). The results were evaluated with analysis of variance (ANOVA), Tukey and Pearson correlation test (α=.05).
The groups containing AgVO3 presented a difference in relation to the control (0%) regarding the release of Ag and V (P<.0001). All groups showed a reduction in L929 viability when compared with the cellular control (100%) (P<.0001). In comparison with the control resins for HP, a reduction in the metabolism of cells occurred starting at 2.5% and for AP at 5% (P<.0001). A positive correlation was found between the concentration of AgVO3 and the ion release, and a negative between the ion release and the cell viability.
Significant numbers of Ag and V ions were released from resins with higher concentrations of AgVO3 , presenting cytotoxicity for cells, suggesting that the use of low concentrations is indicated to avoid risks to patients.

DOI: 10.111/ger.12267


D. H. Nakahata, M. A. Ribeiro, P. P. Corbi, D. Machado, M. Lancellotti, W. R. Lustri, A. M. C. Ferreira & A. L. B. Formiga.
Publicado por Inorganica Chimica Acta, 01/2017

The coordination chemistry and antimicrobial profiles of three copper(II) complexes with 2-(imidazole-2-yl)heteroaryl ligands, named impy, impz and impm, have been investigated. Based on X-ray structure determination the complexes present square planar geometry with coordination formulas [CuCl2(impx)], where x = y, z or m. Elemental analysis and mass spectrometric results are in agreement with the proposed compositions. Vibrational spectroscopy and molecular modeling provided further evidences that the [CuCl2(impz)] complex, which did not have its structure solved by X-ray diffraction, adopts a similar geometry of the other two complexes. Electronic spectroscopic data indicated that all three ligands led to a hypsochromic shift of the d-d band when compared to CuCl2.2H2O and that the electronic structure of the ligands are significantly altered upon coordination to Cu(II). Electronic paramagnetic resonance studies in solution showed that the compounds present similar coordination environments. The MIC values of the complexes over E. coli and S. aureus was 17.8 µmol mL-1 , thus no distinction was found between the complexes and the tested strain. The complexes were inactive over three tested fungal strains under the considered experimental conditions.


B. Possato, V. Deflon, Z. Naal, A. L. B. Formiga & S. Nikolaou.
Publicado por Dalton Transactions, 05/2017

We report on the investigation of a new series of symmetric trinuclear ruthenium complexes combined with azanaphthalene ligands: [Ru3O(CH3COO)6(L)3]PF6 where L = (1) quinazoline (qui), (2) 5-nitroisoquinoline (5-nitroiq), (3) 5-bromoisoquinoline (5-briq), (4) isoquinoline (iq), (5) 5-aminoisoquinoline (5-amiq), and (6) 5,6,7,8-tetrahydroisoquinoline (thiq). The crystal structure of complex 1, [Ru3O(CH3COO)6(qui)3]PF6, was determined by X-ray diffraction analysis, showing a high degree of co-planarity between the [Ru3O] plane and the azanaphthalene ligands. Spectroscopic (UV-visible, NMR and infra-red) and electrochemical (cyclic voltammetry and spectroelectrochemistry) data showed correlation with the pK a values of the azanaphthalene ligands and this dependence was rationalized in terms of the molecular orbital of the [Ru3O] unit and the structure of the ligands. By analysing the spectroscopic and electrochemical correlations, the ability of the azanaphthalene ligands to extend the electronic π-system of the [Ru3O] unit to the periphery of the compounds was demonstrated. This electronic effect accounts for the planarity of the structure of complex 1. It was also shown through molecular modeling results that, to explain the spectroscopic and electrochemical behaviour of these species, it is not possible to neglect the electronic mixing between the metallic and the acetate orbitals. Finally, this work revealed that electronic coupling is more pronounced in the azanaphthalene series of complexes than in pyridinic analogues and it is this coupling that determines the spectroscopic and electrochemical behaviour of the new species.


E. G. R. de Arruda, M. A. de Farias, S. A. V. Jannuzzi, S. A. Gonsales, R. A. Timm, S. Sharma, G. Zoppelaro, L. T. Kubota, M. Knobel & A. L. B. Formiga
Publicado por Inorganica Chimica Acta, 06/2017

The 2,6-di(1H-imidazol-2-yl)pyridine (H2dimpy) ligand is synthesized and suggested as an alternative ligand for copper mediated catalysis. A Cu(II) complex was obtained with this ligand and characterized via ESI-MS, FT-IR, UV–vis and the structure was confirmed by single crystal XRD. The crystal showed the [Cu2 (H2dimpy)2 (µ-Cl)2]PF6.2H2O dimeric complex, in which Cu(II) is in a distorted square-pyramidal geometry (τ=0.301). Ferromagnetic coupling with J=-11.1 cm-1 was confirmed by experiment and corroborated by density functional calculations. In order to evaluate the applicability of H2dimpy in atom transfer radical polymerization (ATRP), polystyrene was produced in DMF solution at low polydispersity (1.3) while maintaining the livingness of the polymer chain. The good performance of the H2dimpy compared to a standard ligand for ATRP (5,5’-dimethyl-2,2’-dipyridyl) indicates that it is suitable for this reaction.


C. M. Manzano, F. R. G. Bergamini, W. R. Lustri, A. L. T. G. Ruiz, E. C. S. Oliveira, M. A. Ribeiro, A. L. B. Formiga & P. P. Corbi
Publicado por Journal of Molecular Structure, 10/2017

Palladium(II) and platinum(II) complexes with a hydrazide derivative of ibuprofen (named HIB) were synthesized and characterized by chemical and spectroscopic methods. Elemental and thermogravimetric analyses, as well as ESI-QTOF-MS studies for both complexes, confirmed a 1:2:2 metal/HIB/Cl- molar ratio. The crystal structure of the palladium(II) complex was solved by single crystal X-ray diffractometric analysis, which permitted identifying the coordination formula [PdCl2(HIB)2]. Crystallographic studies also indicate coordination of HIB to the metal by the NH2 group. Nuclear magnetic resonance and infrared spectroscopies reinforced the coordination observed in the crystal structure and suggested that the platinum(II) complex presents similar coordination modes and structure when compared with the Pd(II) complex. The complexes had their structures optimized with the aid of DFT methods. In vitro antiproliferative assays showed that the [PdCl2(HIB)2] complex is active over ovarian cancer cell line OVCAR-03, while biophysical studies indicated its capacity to interact with CT-DNA. The complexes were inactive over Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacterial strains.


Thiago Augusto Lima Burgo, Bruno C. Bastita & Fernando Galembeck
Publicado por ACS Omega, 12/2017

This work describes the conversion of mechanical energy to electricity, by periodically stretching rubber tubing and allowing it to relax. The rubber surface shows periodic and reversible electrostatic potential variations, in phase with the tubing length. The potential change depends on the elastomer used: silicone loses charge when stretched and becomes strongly negative when relaxed, whereas the stretched natural rubber is positive, becoming negative when relaxed. Every other elastomeric material that was tested also showed periodic potential but followed different patterns. When the motion stops, the potential on the resting samples decreases quickly to zero. The potential oscillation amplitude decreases when the relative humidity decreases from 65 to 27%, but it is negligible when the rubber tubing is previously swollen with water or paraffin oil. Elastomer charging patterns do not present the well-known characteristics of piezo-, flexo-, or triboelectricity, and they are discussed considering rubber rheology, wear, and surface properties, including the possibility of surface piezoelectricity. The following mechanism is suggested: rubber stretching provokes chemical and morphology changes in its surface, followed by a change in the surface concentration of H+ and OH ions adsorbed along with water. The possibility of the occurrence of similar variations in other systems (both inert and biological) is discussed, together with its implications for energy scavenging from the environment.


Elisa S. Ferreira, Douglas S. Da Silva, Thiago Augusto Lima Burgo, Bruno C. Batista & Fernando Galembeck
Publicado por Nanoscale, 07/2017

Shaking graphite powder dispersed in an aqueous alkaline cellulose solution produces stable dispersions of hydrophilic, thin graphite sheets with lateral dimensions reaching many micrometers. The X-ray diffractogram and Raman spectrum of the exfoliated graphite differ from the well-known graphite patterns. Analytical transmission electron micrographs show cellulose bound to the surface of thin lamellae and this is confirmed by scanning probe micrographs. The dispersant properties of dissolved cellulose are assigned to its adsorption on graphite by juxtaposition of the hydrophobic planes on both substances, forming hydrophilic particles. This method uses only simple and easily accessible chemicals, processed under mild conditions. The resulting nanographite-cellulose dispersions are suitable for making conductive lignocellulosic nanocomposites and coatings.

Direct Drawing Method of Graphite onto Paper for High-Performance Flexible Electrochemical Sensors

Murilo Santhiago, Mathias Strauss, Mariane P. Pereira, Andréia S. Chagas, Carlos C.B. Bufon
Publicado por ACS Applied Materials & Interfaces, 03/2017

Reportou pela primeira vez um método simples e rápido de fabricação de sensores eletroquímicos confeccionados a lápis que apresenta um alto desempenho. A transferência de elétrons lenta observada em superfícies confeccionados a lápis foi aprimorada usando duas etapas eletroquímicas: a primeira etapa é realizada a oxidação da superfície e, em seguida, a mesma é reduzida num passo subsequente. A constante heterogenia foi de 5,1 × 10–3 cm s–1, sendo o maior valor relatado até o momento para superfícies confeccionadas a lápis. A origem dessa performance foi mapeada por microscopia de força atômica, espectroscopia de fotoelétron de raio X e espesctroscopia de raman. Os resultados obtidos sugerem que o processo de oxidação leva a transformações químicas e estruturais na superfície do eletrodo. Como prova de conceito, essa superfície confeccionada a lápis foi modificada com azul de meldola a fim de detectar eletrocataliticamente o dinucleótido de nicotinamida adenina (NADH). O dispositivo eletroquímico exibiu a maior constante catalítica (1,7 × 105 L mol-1 s-1) e o menor potencial de detecção de NADH relatado até o momento em eletrodos à base de papel.

Flexible and Foldable Fully-Printed Carbon Black Conductive Nanostructures on Paper for High-Performance Electronic, Electrochemical, and Wearable Devices

Murilo Santhiago, Cátia C. Corrêa, Juliana S. Bernardes, Mariane P. Pereira, Letícia J. M. Oliveira, Mathias Strauss, Carlos C. B. Bufon
Publicado por ACS Applied Materials & Interfaces, 06/2017

O emprego de nanomateriais de carbono totalmente impressos em papel que apresentaram características únicas, visando a fabricação de dispositivos funcionais eletrônicos e eletroquímicos. Foram preparadas tintas modificadas e não modificadas combinando negro de fumo e acetato de celulose para obter trilhas condutoras de alto desempenho e com baixa resistência na folha. As trilhas de negro de carbono resistem a ciclos de dobragem extremamente elevados (> 20000 ciclos), um novo recorde com uma perda de resposta inferior a 10%. Essas trilhas condutoras também foram usadas como células eletroquímicas 3D baseadas em papel que apresentou alto valor de constante heterogênea (1,0(±0,5) × 10−3 cm s−1), uma característica que abre várias possibilidades de aplicações eletroquímicas. Afim de evidenciar uma aplicação relevante, a tinta condutora foi modificada com o Azul Prússia e caracterizada eletroquimicamente mostrando-se muito promissora para a detecção de peróxido de hidrogênio em baixos potenciais. Além disso, os circuitos confeccionados utilizando as trilhas de negro fumo podem ser totalmente amassados e mesmo assim, não apresenta mudanças significativas em sua resposta elétrica. Além disso, foram fabricados sensores de movimento totalmente impressos em que as microfissuras bioinspiradas são criadas na trilha condutora. Os dispositivos portáteis são capazes de controlar eficientemente ângulos de flexão extremamente baixos, incluindo movimentos humanos, dedos e antebraço. Aqui, para o nosso melhor conhecimento, a performance mecânica, eletrônica e eletroquímica dos dispositivos propostos ultrapassa os avanços mais recentes em dispositivos de papel.

The role of the electrode configuration on the electrical properties of small-molecule semiconductor thin-films

Leandro Merces, Rafael Furlan de Oliveira ,Henrique Leonel Gomes, Carlos César Bof Bufon
Publicado por Organic Electronics, 10/2017

This paper presents a systematic analysis of the electrode configuration influence on the electrical properties of organic semiconductor (OSC) thin-film devices. We have fabricated and electrically characterized a set of planar two-terminal devices. The differences in I-V characteristics between the top and bottom contact structures are presented and analyzed. Top-contact configurations have a linear current vs. electric field behavior, while the bottom-electrode devices display a transition from ohmic to space-charge-limited conduction regime. The transition is temperature- and thickness-dependent. Finite-element calculations show that when the OSC film is connected using top electrodes, the current flows through the OSC bulk region. On the other hand, the bottom-electrode configuration allows most of the current to flow near the OSC/substrate interface. The current probes the interfacial states, resulting in a space-charge conduction regime. The results shed some light on the so-called “contact effects” commonly observed in organic thin-film transistors. The findings presented here have implications for both the understanding of the charge transport in OSC films and the design of organic semiconductor devices.

Long-Range Coherent Tunneling in Physisorbed Molecular Ensembles

Leandro Merces, Rafael Furlan de Oliveira, Davi Henrique Starnini de Camargo, Carlos César Bof Bufon
Publicado por The Journal of Physical Chemistry C, 05/2017

O transporte de carga em sistemas moleculares é governado por uma série de interações quânticas entre moléculas e portadores, resultando em um vasto conjunto de fenômenos químicos e físicos. O controle preciso destes fenômenos é um dos principais desafios no desenvolvimento de conceitos inovadores de dispositivos. Nos sistemas moleculares, o tunelamento direto (através de barreiras de 1 a 10 nm) e a condução por hopping (através de distâncias maiores) têm sido descritos como os mecanismos de transporte predominantes. A transição contínua de um para o outro, como função da distância de transporte, tem sido reportada principalmente para moléculas adsorvidas quimicamente aos eletrodos. O conjunto elementar de junções moleculares formadas por moléculas adsorvidas fisicamente, entretanto, permanece inexplorado do ponto de vista da transição entre o transporte coerente e a condução ativada. Neste trabalho, a primeira evidência experimental de tunelamento sequencial coerente é reportada para conjuntos moleculares adsorvidos fisicamente. A investigação foi conduzida tendo como base o estudo do transporte eletrônico em conjuntos finos e ultrafinos de ftalocianina de cobre (com espessuras de 5 a 60 nm). Como observado para estruturas adsorvidas quimicamente, uma transição gradual de tunelamento coerente para condução com ativação térmica foi observada entre 10 e 22 nm. Assim, este trabalho contribui para conectar o fenômenos quânticos do transporte na nano escala aos fenômenos difusivos para o referido sistema elementar de moléculas adsorvidas fisicamente.

A simple capacitive method to evaluate ethanol fuel samples

Tatiana Parra Vello, Rafael Furlan de Oliveira, Gustavo Oliveira Silva, Davi Henrique Starnini de Camargo, Carlos César Bof Bufon
Publicado por Scientific Reports, 02/2017

O etanol é um biocombustível usado em todo o mundo. No entanto, a presença de excesso de água durante o processo de destilação ou por adulteração fraudulenta é uma das principais preocupações no uso de etanol combustível. Altos níveis de água podem causar mau funcionamento do motor, além de serem considerados ilegais. Aqui, descrevemos o desenvolvimento de uma plataforma simples, rápida e precisa baseada em sensores nanoestruturados para avaliar amostras de etanol. A fabricação do dispositivo é fácil, baseada em microfabricação padrão e métodos de deposição de filme fino. A operação do sensor depende de medições de capacitância empregando um capacitor de placa paralela contendo uma camada fina de óxido de alumínio conformacional (Al2O3) (15 nm). O sensor opera sobre toda a faixa de concentração de água, isto é, de aproximadamente 0% a 100% vol. de água em etanol, com traços de água detectáveis ​​até 0,5% vol. Essas características tornam o dispositivo proposto único em relação a outras plataformas. Finalmente, a boa concordância entre a resposta do sensor e as análises realizadas por cromatografia gasosa do etanol biocombustível endossa a precisão do método proposto. Devido à faixa de operação completa, o sensor relatado tem o potencial tecnológico para uso como uma ferramenta analítica de ponto de atendimento em postos de gasolina ou nas indústrias química, farmacêutica e de bebidas, para mencionar alguns.

Unveiling One‐Dimensional Supramolecular Structures Formed through π–π Stacking of Phenothiazines by Differential Pulse Voltammetry

Fernando R. Carvalho; Eduardo H. Zampieri;Wilker Caetano; Rafael Silva
Publicado por ChemPhysChem, 03/2017

Organic‐based nanomaterials can be self‐assembled by strong and directional intermolecular forces such as π–π interactions. Experimental information about the stability, size, and geometry of the formed structures is very limited for species that easily aggregate, even at very low concentrations. Differential pulse voltammetry (DPV) can unveil the formation, growth, and also the stability window of ordered, one‐dimensional, lamellar self‐aggregates formed by supramolecular π stacking of phenothiazines at micromolar (10−6 mol L−1) concentrations. The self‐diffusion features of the species at different concentrations are determined by DPV and used to probe the π staking process through the concept of the frictional resistance. It is observed that toluidine blue and methylene blue start to self‐aggregate around 9 μmol L−1, and that the self‐aggregation process occurs by one‐dimensional growth as the concentration of the phenothiazines is increased up to around 170 μmol L−1 for toluidine blue and 200 μmol L−1 for methylene blue. At higher concentrations, the aggregation process leads to structures with lower anisometry.

Hybrid Materials and Nanocomposites as Multifunctional Biomaterials

Heveline D. M. Follmann, Alliny F. Naves, Rafael A. Araujo, Viktor Dubovoy, Xiaoxi Huang, Tewodros Asefa, Rafael Silva, Osvaldo N. Oliveira
Publicado por Current Pharmaceutical Design, 08/2017

This review article provides an overview of hybrid and nanocomposite materials used as biomaterials in nanomedicine, focusing on applications in controlled drug delivery, tissue engineering, biosensors and theranostic systems. Special emphasis is placed on the importance of tuning the properties of nanocomposites, which can be achieved by choosing appropriate synthetic methods and seeking synergy among different types of materials, particularly exploiting their nanoscale nature. The challenges in fabrication for the nanocomposites are highlighted by classifying them as those comprising solely inorganic phases (inorganic/inorganic hybrids), organic phases (organic/organic hybrids) and both types of phases (organic/inorganic hybrids). A variety of examples are given for applications from the recent literature, from which one may infer that significant developments for effective use of hybrid materials require a delicate balance among structure, biocompatibility, and stability.

Poisoning Effects of Water and Dyes on the [Bmim][BF4] Catalysis of Poly(Ethylene Terephthalate) (PET) Depolymerization under Supercritical Ethanol

Cátia S. Nunes , Paulo R. Souza, Adonilson R. Freitas, Michael Jackson Vieira da Silva, Fernanda A. Rosa, Edvani C. Muniz
Publicado por Catalysts, 01/2017

Supercritical ethanolysis (scEtOH) is a method that allows the production of monomers,e.g., diethyl terephthalate (DET), from Polyethylene terephthalate PET chemical recycling. The use of the ionic liquids (ILs) such as 1-n-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) as a catalyst has advantages in such processes by enhancing the yield at reduced times, as shown in previous work from our lab. However, the effects of water and dyes (from the coloured PET-bottles) regarding those advantages have not been investigated. Here, a study of the effects of water and dyes on IL-catalysis is provided. Results showed that the yield related to DET formation was 98% when anhydrous ethanol was employed, but decreased to 30% (or less) when water was present in the reaction even in low amounts. Furthermore, the DET-formation yield also decreased to 66% orto 21% if 2-aminoanthraquinone or zinc phthalocyanine were present, respectively, even inanhydrous conditions. Poisoning effect on the IL-catalysis was observed in both cases. Thus, these data are relevant for expanding the study of ILs as catalysts in this and other reaction systems.

Chondroitin sulfate immobilization at the surface of electrospun nanofiber meshes for cartilage tissue regeneration approaches

Juliana FrancisPiai; Marta Alvesda Silva; AlbinoMartins; Ana BelaTorres; SusanaFaria; Rui L.Reis; Edvani CurtiMuniz; Nuno M.Neves
Publicado por Applied Surface Science, 08/2017

Aiming at improving the biocompatibility of biomaterial scaffolds, surface modification presents a way to preserve their mechanical properties and to improve the surface bioactivity. In this work, chondroitin sulfate (CS) was immobilized at the surface of electrospunpoly(caprolactone) nanofiber meshes (PCL NFMs), previously functionalized by UV/O3 exposure and aminolysis. Contact angle, SEM, optical profilometry, FTIR, X-ray photoelectron spectroscopy techniques confirmed the success of CS-immobilization in PCL NFMs. Furthermore, CS-immobilized PCL NFMs showed lower roughness and higher hydrophilicity than the samples without CS. Human articular chondrocytes (hACs) were cultured on electrospun PCL NFMs with or without CS immobilization. It was observed that hACs proliferated through the entire time course of the experiment in both types of nanofibrous scaffolds, as well as for the production of glycosaminoglycans. Quantitative-PCR results demonstrated over-expression of cartilage-related genes such as Aggrecan, Collagen type II, COMP and Sox9 on both types of nanofibrous scaffolds. Morphological observations from SEM and LSCM revealed that hACs maintained their characteristic round shape and cellular agglomeration exclusively on PCL NFMs with CS immobilization. In conclusion, CS immobilization at the surface of PCL NFMs was achieved successfully and provides a valid platform enabling further surface functionalization methods in scaffolds to be developed for cartilage tissue engineering.

Chitosan/chondroitin sulfate hydrogels prepared in [Hmim][HSO 4 ] ionic liquid

Cátia S. Nunes; Kessily B. Rufato; Paulo R. Souza; Elizângela A. M. S. de Almeida; Michael J. V. da Silva; Débora B.Scariot; Celso V. Nakamura; Fernanda A. Rosa; Alessandro F.Martins; Edvani C. Muniz
Publicado por Carbohydrate Polymers, 08/2017

[Hmim][HSO4] ionic liquid (IL) and bio-renewable sources as chitosan (CHT) and chondroitin sulfate (CS) were used to yield hydrogel-based materials (CHT/CS). The use of IL to solubilize both polysaccharides was considered an innovative way based on “green chemistry” principle, aiming the production of CHT/CS blended systems. CHT/CS hydrogels were carried out in homogeneous medium from short dissolution times. The hydrogels were characterized and achieved with excellent stabilities (in the 1.2–10 pH range), larger swelling capacities, as well as devoid of cytotoxicity towards the normal VERO and diseased HT29 cells. The CHT/CS hydrogels carried out in [Hmim][HSO4] could be applied in many technological purposes, like medical, pharmaceutical, and environmental fields.

Adsorption and controlled release of potassium, phosphate and ammonia from modified Arabic gum-based hydrogel

Fernanda Zonatto; Edvani C.Muniz; Elias B.Tambourgi; Alexandre T.Paulino
Publicado por International Journal of Biological Macromolecules, 12/2017

In this work, a modified Arabic gum-based hydrogel copolymerized with acrylamide was synthesized and characterized for application in adsorption and controlled release of potassium, phosphate and ammonia. From FT-IR results, it would be reasonable to assume that the hydrogel was effectively synthesized. The degree of swelling at pure water with pH 6.0 was 21.0 g water per g dried hydrogel whereas the degrees of swelling at buffer solutions with pH 4.5 and 7.0 were 7.2 and 9.2 g water per g dried hydrogel, respectively. The water diffusion mechanism was governed by Fickian transport with tendency to occur macromolecular relaxation. The adsorption capacities of potassium, phosphate and ammonia were higher by increasing the initial concentrations due to availability of active sites in the hydrogel network, nutrient size and ionic charge. Potassium, phosphate and ammonia concentrations released from the modified Arabic gum-based hydrogel increased by increasing the release time from 0 to 1440 min. Release profiles indicated that this hydrogel could be applied for the enrichment and hydration of deserted soil, avoiding losses of nutrients by leaching and percolation, with an advantage of being constituted by an eco-friendly polysaccharide.

Polyelectrolyte complexes based on alginate/tanfloc: Optimization, characterization and medical application

Débora P.Facchi; Ana C.Lima; Jean Oliveira; Danielle Lazarin-Bidóia; Celso V.Nakamura; Edmilson A.Canesin; Elton G.Bonafé; Johny P.Monteiro; Jesuí V.Visentainer; EdvaniC.Muniz; Alessandro F.Martins
Publicado por International Journal of Biological Macromolecules, 10/2017

Hydrogels based on alginate and tanfloc (a cationic biopolymer obtained from natural condensed tannins) were successfully prepared. Tanfloc (TN) presents high aqueous solubility at pHs lower than 10; it contains substituted amino sites and molar weight of ca. 600,000 g mol−1. A factorial design (22) was used to optimize the yield of alginate/tanfloc polyelectrolyte complexes (PECs). Dialysis recovered the overplus of alginate (AG) no complexed with TN. These materials were characterized by thermal analyses (TGA/DTG and DSC), zeta potential, and FTIR, while SEM technique depicted a rough surface on AG/TN complex, containing non-homogeneous pores. Indeed, the AG and TN were tailored to elicit scaffold materials with outstanding cytocompatibility, mainly upon mouse preosteoblastic cells because of reconstruction of bone tissues (119% at 10 days). The AG/TN complex also displayed antioxidant and bactericidal activities against Staphylococcus aureus (S. aureus). Besides, the pristine TN fostered bacteriostatic and bactericidal performances towards S. aureus and Escherichia coli. However, for our best knowledge, no studies were still carried out on TN and TN-based materials for medical purpose.

Scaffolds based on chitosan/pectin thermosensitive hydrogels containing gold nanoparticles

Fábio R. Tentor; Jean H. de Oliveira; Débora B. Scariot; Danielle Lazarin-Bidóia; Elton G. Bonafé; Celso V. Nakamura; Sandro A. S. Venter; Johny P.Monteiro; Edvani C.Muniz; Alessandro F.Martins
Publicado por International Journal of Biological Macromolecules, 09/2017

Thermosensitive hydrogels based on chitosan/pectin (CS/Pec) and CS/Pec/gold nanoparticles (CS/Pec/AuNPs) were successfully prepared with different AuNP levels. Using a tilting method, gelation temperature was demonstrated to decrease when the amount of AuNPs increased and pectin concentrations decreased. The presence of AuNPs in the CS/Pec composite was evaluated via WAXS and UV–vis techniques, while SEM analysis assessed the average size of pores (350–600 μm). All samples were extremely cytocompatible with many cell types, such as normal kidney epithelial cells (VERO cells), epithelial colorectal adenocarcinoma cells (HT-29 cells), HPV-16 positive human cervical tumour cells (SiHa cells), kidney epithelial cells (LLCMK2 cells) and murine macrophage cells (J774A1 cells). Cell viability assays using the MTT method upon mouse preosteoblastic cells (MC3T3-E1 cells) showed that CS/Pec and CS/Pec/AuNPs composites had the potential to foster proliferation and growth of bone cells, making them possible stimulators for reconstruction of bone tissues.

Polysaccharide-Based Materials Associated with or Coordinated to Gold Nanoparticles: Synthesis and Medical Application.

Débora P. Facchi, Joziel A. da Cruz, Elton G. Bonafé, Antonio G. B. Pereira, André R. Fajardo, Sandro A. S. Venter, Johny P. Monteiro, Edvani C. Muniz, Alessandro F. Martins*
Publicado por Current Medicinal Chemistry, 01/2017

Background: Gold nanoparticles (AuNPs) have enormous potential for application in imaging, diagnosis, and therapies in the medical field. AuNPs are renowned for their localized surface plasmon resonance (LSPR) properties, large surface area, and biocompatibility with body fluids. Further, AuNPs have featured prominently in new methodologies for cancer treatments, like photothermal and imaging therapies. Although AuNPs present enormous potential for application in the medical field, their instability under physiological conditions prevents further uses. However, this limitation may be overcome by associating AuNPs with biopolymers. To the best of our knowledge, a revision paper rationalizing the structure/property relationship and applications of AuNPspolysaccharide composites in the medical field has not been published yet.Methods: This manuscript discusses the most relevant aspects and state-of-art concepts surrounding the synthesis of AuNPs based on green chemistry and their association with polysaccharides that can efficiently function both as stabilizing and reducing agents of Au nanoparticles. Even more, polysaccharide devices may inhibit non-specific interactions between AuNPs and biological macromolecules, suppressing unsuitable “protein corona” formations on AuNP surfaces, thereby increasing the potential of AuNP composites of being employing as drug delivery matrices and wound-healing devices as well as in photothermal/ imaging purposes for cancer treatments and biosensors.

From ionic liquid-modified cellulose nanowhiskers to highly active metal-free nanostructured carbon catalysts for the hydrazine oxidation reaction

Elizângela H. Fragal, Vanessa H. Fragal, Xiaoxi Huang, Alessandro C. Martins, Thelma Sley P. Cellet, Guilherme M. Pereira, Eliška Mikmeková, Adley F. Rubira, Rafael Silva and Tewodros Asefa
Publicado por Journal of Materials Chemistry A, 03/2017

Ionic liquid (or [C4mim][CH3SO3])-modified cellulose nanowhiskers (CNWs) are synthesized and successfully used as precursors to make heteroatom (N and S)-doped nanostructured carbon catalysts. The catalysts can efficiently electrocatalyze the hydrazine oxidation reaction (HOR) with an onset potential close to the reaction's thermodynamic value, or with a value better than those obtained for other related materials. The synthesis of these metal-free carbon electrocatalysts generally involves only a few, relatively less demanding synthetic steps. Based on relevant control experiments, the outstanding catalytic activity of the materials is attributed to the heteroatom dopants and defect sites in the materials, which form during carbonization due to the [C4mim][CH3SO3] placed around the CNWs. However, it is not necessarily the density of heteroatom dopant species introduced into the nanostructured carbon materials by the ILs that directly affect the electrocatalytic activity of these materials; it is rather the specific type of dopant-associated chemical moiety and vacancy site created in the materials, which are the main factors positively affecting the electrocatalytic activity of the materials toward the reaction. The surface areas of the materials play a relatively lesser role in affecting the electrocatalytic properties of the materials toward the HOR as well.

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles

Fernanda G. Santos, Letícia C. Bonkovoski, Francielle P. Garcia, Thelma S. P. Cellet, Maria A. Witt, Celso V. Nakamura, Adley F. Rubira, and Edvani C. Muniz
Publicado por ACS Applied Materials and Interface, 02/2017

In the present study, nanofiber meshes (NFs), composed of polycaprolactone and poly[(2-dimethylamino)ethyl methacrylate] at 80/20 and 50/50 PCL/PDMAEMA blend ratios, were obtained through electrospinning. Silver nanoparticles (AgNPs) formed in situ were then immobilized on NF surfaces through adsorption processes at different pHs. It was possible to observe that the amount of NF-AgNPscan be tuned by changing the pH of AgNPs immobilization and the PCL/PDMAEMA ratio in the blend. The neat NF and NF-AgNPswere characterized with respect to their morphology and mechanical properties. The effects of AgNPs on the antibacterial activities and cytotoxicity of meshes were also evaluated. The antibacterial performance of such NF was improved by the presence of AgNPs. The NF-AgNPs presented good antibacterial effect against S. aureus and partial toxicity against E. coli and P. aeruginosa. Also, compared with neat PCL/PDMAEMA the NF-AgNPs presented lower cytotoxicity against VERO cells, showing their potential for applications in tissue engineering for different types of cell growth.

Synthesis and drug release profile of a dual-responsive poly(ethylene glycol) hydrogel nanocomposite

Ernandes Taveira Tenório-Neto,Diego de Souza Lima, Marcos Rogério Guilherme, Michele Karoline Lima-Tenório, Débora Botura Scariot, Celso Vataru Nakamura, Marcos Hiroiuqui Kunita, Adley Forti Rubira
Publicado por RSC Advances, 05/2017

This work describes the synthesis, characterization and application of a pH- and magnetic-responsive PEG hydrogel (HG) nanocomposite as a platform for drug delivery. PEG was used to produce permanent hydrogels with improved biocompatibility. A specific cross-linking/copolymerization chemistry was used to construct hydrogels with a controlled network organization so as not to affect the PEG biocompatibility. The hydrogels were prepared using vinylated PEG together with DMAAm, acrylic acid, and iron oxide nanoparticles. The water affinity, morphology, drug release profile and cytotoxicity of the resulting materials were studied in depth. The designed hydrogels were shown to be materials of biological relevance and of great pharmacological potential as drug carriers in drug delivery.

Trapped Metallic Cobalt Nanoparticles in Doped Porous Graphite: An Electrocatalyst that Gets Better Over Reaction Time.

Guilherme M. Pereira; Thelma S. P. Cellet; Ricardo H. Gonçalves; Adley F. Rubira; Rafael Silva
Publicado por Applied Catalysis B: Environmental, 11/2017

Hybrid materials synthesis is a pathway to integrating unstable inorganic phases in a protective matrix, as an approach to phase stabilization in harsh environments and to use the unique catalytic properties of such metastable phases. Here, we show a polymer precursor method to synthesize nitrogen-doped carbon nanomaterials from melamine-formaldehyde resin with Co2+ ions coordinated in the precursor material. Co2+ ions are reduced during the pyrolysis process to form metallic nanoparticles. Nitrogen-doped carbon nanotubes, with high nitrogen content, are obtained at pyrolysis temperature of 800 °C or 900 °C. When lower temperature is used (i.e. 700 °C), porous amorphous carbon is obtained. At the highest temperature used (1000 °C), carbon matrix with low nitrogen content is produced, having porous graphitic carbon structure. Graphitic carbon structure and metallic cobalt showed impressive catalytic activity toward water electrooxidation reaction, similar to benchmark catalysts for OER. The stability studies of the electrocatalyst showed an extraordinary 52% current density improvement in the first 8 h of OER, and then a very stable pattern is verified. After 12 h of applied potential, Tafel slope decreases to 57 mV dec−1, which is characteristic of very fast surface kinetics, and therefore it is a promising material to become a reliable alternative to anode manufacture for OER.

Curcumin-loaded dual pH- and thermo-responsive magnetic microcarriers based on pectin maleate for drug delivery

Elizângela A.M.S. Almeida; Ismael C. Bellettini; Francielle P. Garcia; Maroanne T. Farinácio; Celso V. Nakamura; Adley F. Rubira; Alessandro F. Martins; Edvani C. Muniz
Publicado por Carbohydrate Polymers, 10/2017

Magnetic microgels with pH- and thermo-responsive properties were developed from the pectin maleate, N-isopropyl acrylamide, and Fe3O4 nanoparticles. The hybrid materials were characterized by infrared spectroscopy, scanning electron microscope coupled with X–ray energy dispersive spectroscopy, wide angle X–ray scattering, Zeta potential, and magnetization hysteresis measurements. Curcumin (CUR) was loaded into the microgels, and release assays were carried out in simulated environments (SGF and SIF) at different conditions of temperature (25 or 37 °C). A slow and sustainability CUR release was achieved under external magnetic field influence. Loaded CUR displayed stability, bioavailability and greater solubility regarding free CUR. Besides, the cytotoxicity assays showed that magnetic microgels without CUR could suppress the Caco-2 cells growth. So, the pectin maleate, N-isopropyl acrylamide, and Fe3O4 could be tailored to elicit hybrid-based materials with satisfactory application in the medical arena.

Interactions between copper(II) dibrominatedsalen complex and copolymeric micelles of P-123 and F-127

Vilsinski, Bruno H.); Murtinho, Dina M. B.; Serra, Maria E. S.; Soares, Edna F. P.; Cruz, Pedro F.; Braga, Gustavo; Borges, Olga; Muniz, Edvani C.; Rubira, Adley F.; Caetano, Wilker; Valente, Artur J. M.
Publicado por Colloids and Surfaces A-Physicochemicaland Engineering Aspects, 11/2017

Metal-salen complexes have been extensively studied for several applications in nanomedicine as chemotherapic agents substituting, for example, cisplatin based compounds. A recently synthesized copper(II) dibrominatedsalen complex (Cu-salenBr(2)) has shown excellent preliminary results against different cell lines; however, its poor water solubility is a major drawback for the use of Cu-salenBr(2) in biological fluids. In order to overcome this limitation, Cu-salenBr(2) was incorporated in biocompatible micellar systems of Pluronics surfactants F-127 and P-123 by the solid dispersion method, aiming at both the increase in the bioavailability of the complex and the development of a(CusalenBr(2)/copolymer) formulation for intravenous application. The Cu-salenBr(2) formulations were characterized by UVvis and infrared spectroscopies; this has been complemented by studies on the effect of concentration on the self-diffusion coefficients of micelles. The encapsulation efficiency and the thermal and kinetics stability of Pluronic-Cu-salenBr(2) formulations were studied. From these studies, it has been found that P-123-containing formulations are more stable and, consequently, they were chosen for cytotoxicity studies. The cytotoxicity of Cu-salenBr(2) against fibroblast-like kidney cells (COS-7) and BALB/c mice spleen cells was evaluated, either alone or incorporated in P-123. No significant cytotoxicity was observed for Cu-salenBr(2), per se, dissolved in the culture medium, however, Cu-salenBr(2) solubilized in DMSO/DMEM and Cu-salenBr(2)/P-123 formulation showed a concentration dependent toxic effect on both COS-7 cell line and mouse spleen cells. The IC50 values obtained for the Cu-salenBr(2)/P-123 formulation were 0.41 and 1.6 molL(-1) for spleen and COS-7 cells, respectively.

Recent Advances in Designing Hydrogels from Chitin and Chitin-Derivatives and their Impact on Environment and Agriculture: A Review.

Pereira, A. G. B.; Martins, A. F.; Paulino, A. T.; Fajardo, A. R.; Guilherme, M. R.; Faria, M. G. I.; Linde, G. A.; Rubira, A. F.; Muniz E. C.
Publicado por Revista Virtual da Química, 01/2017

Nosso objetivo é mostrar e discutir os dados mais relevantes sobre a abordagem de síntese e a caracterização de hidrogéis à base de quitina e derivados de quitina, como a quitosana,bem como suas aplicações em diversas tecnologias de materiais. A relevância atual e futura dos materiais à base de quitina, quitosana e derivados foi verificada pelo impressionante número de publicações científicas e tecnológicas (tanto papéis como patentes) que aparecem no dia-a-dia. Os hidrogéis, que apresentam propriedades semi-líquidas e semi-sólidas, tornaram-se uma grande promessa para aplicações onde o uso eficiente da água é essencial para melhorar as propriedades físico-químicas dos solos áridos. Eles também são eficazes no tratamento de águas contaminadas com corantes, chumbo cádmio, mercúrio, níquel e assim por diante, minimizando o impacto ambiental.

Bacterial cellulose nanocrystals produced under different hydrolysis conditions: Properties and morphological features

Niédja Fittipaldi Vasconcelos, Judith Pessoa Andrade Feitosa, Francisco Miguel Portela da Gama, João Paulo Saraiva Morais, Fábia Karine Andrade, Men de Sá Moreira de Souza Filho, Morsyleide de Freitas Rosa
Publicado por Carbohydrate Polymers, 01/2017

Bacterial cellulose (BC) is a polymer with interesting physical properties owing to the regular and uniform structure of its nanofibers, which are formed by amorphous (disordered) and crystalline (ordered) regions. Through hydrolysis with strong acids, it is possible to transform BC into a stable suspension of cellulose nanocrystals, adding new functionality to the material. The aim of this work was to evaluate the effects of inorganic acids on the production of BC nanocrystals (BCNCs). Acid hydrolysis was performed using different H2SO4 concentrations and reaction times, and combined hydrolysis with H2SO4 and HCl was also investigated. The obtained cellulose nanostructures were needle-like with lengths ranging between 622 and 1322 nm, and diameters ranging between 33.7 and 44.3 nm. The nanocrystals had a crystallinity index higher than native BC, and all BCNC suspensions exhibited zeta potential moduli greater than 30 mV, indicating good colloidal stability. The mixture of acids resulted in improved thermal stability without decreased crystallinity.

Optimization of the acetosolv extraction of lignin from sugarcane bagasse for phenolic resin production

Francisca Gleyciara Cavalcante Pinheiro, Amanda Kelly Lima Soares, Sandra Tédde Santaella, Lorena Mara Alexandre e Silva, Kirley Marques Canuto, Carlos Alberto Cáceres, Morsyleide de Freitas Rosa, Judith Pessoa de Andrade Feitosa, Renato Carrhá Leitão
Publicado por Industrial Crops and Products, 02/2017

The experimental central composite design 22 was applied to optimize the acetosolv process for lignin extraction from sugarcane bagasse, with an aim to replace the petroleum-derived phenols conventionally used for resin production. The highest acetosolv extraction yield (55% ± 4.5%) was achieved with an acetic acid concentration of 95% (w/w), containing 0.1% (v/v) HCl, at 187 °C for 40 min. Other optimal conditions for extraction, such as 187 °C, 15 min (OC187;15) and 205 °C, 15 min (OC205;15), were calculated from statistical models. The optimized acetosolv lignins were characterized by thermal analysis (TGA and DSC), size exclusion chromatography, and spectroscopic methods (FT-IR and HSQC-NMR). Compared to Kraft lignin, they exhibited higher thermal stability, low molar mass, p-hydroxyphenyl units as their major constituent, higher relative phenolic and total hydroxyl contents, and lower relative methoxyl group content. Accordingly, optimized acetosolv lignins seem to have structural features suitable for phenol-formaldehyde resin synthesis.

Quaternized cashew gum: An anti-staphylococcal and biocompatible cationic polymer for biotechnological applications

Patrick V. Quelemes, Alyne Araújo, Alexandra Plácido, Cristina Delerue-Matos, Jeanny S. Maciel, Lucinda J.Bessa, Alicia S.Ombredane, Graziella A. Joanitti, Maria José dos S. Soares, Peter Eaton, Durcilene A. da Silva, José Roberto S.A.Leite
Publicado por Carbohydrate Polymers, 02/2017

Chemical modifications to cashew gum (CG) structure have been previously reported to obtain new physicochemical characteristics, however until now there were no reports of modifications by introduction of new functional groups to add cationic character. This study presents a quaternization route for CG using a quaternary ammonium reagent. The chemical features of the quaternized cashew gum derivatives (QCG) were analyzed by: FTIR, elemental analysis, degree of substitution, Zeta potential, 1H NMR and 1H-13C correlation (HSQC). QCG were evaluated for their anti-staphylococcal activity by determining minimum inhibitory and bactericidal concentrations against pathogenic Staphylococcus spp. and by imaging using atomic force microscopy. Moreover, the mammalian cell biocompatibility were also assessed through hemolytic and cell toxicity assays. QCG presented promising antimicrobial activity against methicillin-resistant S. aureus and biocompatibility on tested cells. These results show that QCG could be a promising tool in the development of biomaterials with an anti-septic action.

Composite Superabsorbent Hydrogel of Acrylic Copolymer and Eggshell: Effect of Biofiller Addition

Marcos Vinícius A. Queirós, Maslândia N. Bezerra, Judith P. A. Feitosa
Publicado por J. Braz. Chem. Soc., 03/2017

Eggshell (ES) is an abundant waste material which is mainly composed of calcium carbonate. A superabsorbent hydrogel composite based on poly(acrylamide-co-potassium acrylate) as matrix containing 17 wt.% of chicken ES powder as a filler was synthesized and compared with the gel without filler. The characterization was carried out by Fourier transform infrared (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), rheological analysis and kinetics studies. The dispersion of ES in the polymeric matrix was homogeneous. The interaction between the acrylate and calcium cation was detected by FTIR analysis. The composite improved the gel strength and the absorption of water and saline solution increased by 100 and 41%, respectively. The high values for the swelling, the homogeneous structure and the good mechanical properties obtained with the incorporation of a relatively high content of a low-cost waste material indicate that this composite is suitable for application in the agriculture. In addition, this approach provides a more ecologically sound and useful destination for eggshell residue.

Matrix Effect on the Spray Drying Nanoencapsulation of Lippia sidoides Essential Oil in Chitosan-Native Gum Blends

Haroldo C. B. Paula, Erick F. Oliveira, Maria J. M. Carneiro, Regina C. M. de Paula
Publicado por Planta Medica, 03/2017

Essential oils have many applications in the pharmaceutical, chemical, and food fields, however, their use is limited to the fact that they are very labile, requiring their a priori encapsulation, aiming to preserve their properties. This work reports on the preparation of chitosan-gum nanoparticles loaded with thymol containing Lippia sidoides essential oil, using exudates of Anacardium Occidentale (cashew gum), Sterculia striata (chicha gum), and Anadenanthera macrocarpa trees (angico gum). Nanoparticles were produced by spray drying an emulsion of L. sidoides essential oil and aqueous solution of gums with different chitosan: gum ratios. Samples were characterized by FTIR and UV/VIS spectroscopy, particle size, volume distribution, and zeta potential. The FTIR spectrum showed the main signals of chitosan and the gums. Data obtained revealed that the samples had sizes in the nano range, varying from 17 nm to 800 nm. The zeta potential varied from + 30mV to -40mV. Nanoparticle loading values varied from 6.7% to 15.6%, with an average encapsulating efficiency of 62%, where the samples with high ratios of cashew gum and chicha gum presented high oil loading values. The data revealed that both the chitosan: gum ratio and polysaccharide characteristics play major roles in nanoencapsulation processes.

Application of cashew tree gum on the production and stability of spray-dried fish oil

Diego Alvarenga Botrel, Soraia Vilela Borges, Regiane Victória de Barros Fernandes, Rosemar Antoniassi, Adelia Ferreira de Faria-Machado, Judith Pessoa de Andrade Feitosa, Regina Celia Monteiro de Paula
Publicado por Food Chemistry, 04/2017

Evaluation of cashew gum compared to conventional materials was conducted regarding properties and oxidative stability of spray-dried fish oil. Emulsions produced with cashew gum showed lower viscosity when compared to Arabic gum. The particle size was larger (29.9 μm) when cashew gum was used, and the encapsulation efficiency reached 76%, similar to that of modified starch but higher than that for Arabic gum (60%). The oxidation process for the surface oil was conducted and a relative lower formation of oxidation compounds was observed for the cashew gum treatment. GAB model was chosen to describe the moisture adsorption isotherm behaviours. Microparticles produced using Arabic and cashew gums showed greater water adsorption when exposed to higher relative humidities. Microparticles produced using cashew gum were more hygroscopic however encapsulation efficiency were higher and surface oil oxidation were less pronounced. Cashew gum can be further explored as an encapsulant material for spray drying processes.

Binderless Fiberboards Made from Unripe Coconut Husks

Celso Pires Araújo Junior, Carlos Alberto Cáceres Coaquira, Adriano Lincoln Albuquerque Mattos, Men de Sá Moreira de Souza Filho, Judith Pessoa de Andrade Feitosa, João Paulo Saraiva de Morais, Morsyleide de Freitas Rosa
Publicado por Waste and Biomass Valorization, 08/2017

With the growing consumption of coconut water, high amounts of wastes that are hard to manage are produced. Such biomass should be recycled for reducing the accumulation of trash, adding value to the supply chain and generating profits, and increasing the useful lifetime of landfills. White coir contains high amounts of lignin, which can act as a natural binder under suitable conditions of pressure and temperature. Synthetic resins derived from petroleum are commonly used as fiberboard binders; however, they are potentially cancer promoters. Furniture, wallboard, floors, and coatings can be produced using coir-based fiberboards without needing to cut down trees. This study investigated the potential of coconut husks as a raw material for binderless fiberboards. The fiberboards were characterized by thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The swelling, water uptake, and the mechanical properties of the fiberboards were also examined. The use of high temperatures results in the production of fiberboards exhibiting an enhanced water resistance, in accordance with the standard procedure ABNT NBR 15316-2:2015 for High-density fiberboards (HDF). HDF were successfully fabricated in the absence of additional binders. The pressing temperature plays an important role in determining the material characteristics.

The potential of cashew gum functionalization as building blocks for layer-by-layer films

Álvaro J. Leite, Rui R. Costa, Ana M. S. Costa, Jeanny S. Maciel, José F. G. Costa, Regina C. M. de Paula, João F. Mano
Publicado por Carbohydrate Polymers, 10/2017

Cashew gum (CG), an exudate polysaccharide from Anacardium occidentale trees, was carboxymethylated (CGCm) and oxidized (CGO). These derivatives were characterized by FTIR and zeta potential measurements confirming the success of carboxymethylation and oxidation reactions. Nanostructured multilayered films were then produced through layer-by-layer (LbL) assembly in conjugation with chitosan via electrostatic interactions or Schiff bases covalent bonds. The films were analyzed by QCM-D and AFM. CG functionalization increased the film thickness, with the highest thickness being achieved for the lowest oxidation degree. The roughest surface was obtained for the CGO with the highest oxidation degree due to the predominance of covalent Schiff bases. This work shows that nanostructured films can be assembled and stabilized by covalent bonds in alternative to the conventional electrostatic ones. Moreover, the functionalization of CG can increase its feasibility in multilayers films, widening its potential in biomedical, food industry, or environmental applications.

Properties of spray-dried fish oil with different carbohydrates as carriers

Diego Alvarenga Botrel, Soraia Vilela Borges, Maria Irene Yoshida, Judith Pessoa de Andrade Feitosa, Regiane Victória de Barros Fernandes, Hugo Junior Barboza de Souza, Regina Célia Monteiro de Paula
Publicado por Journal of Food Science and Technology, 12/2017

This study evaluated the application of cashew gum, Arabic gum and starch on physical and thermal properties, and fatty acid profiles of spray-dried fish oil. A completely randomized design was used to evaluate the influence of the type of material on the properties of the microparticles. Hygroscopicity and solubility was higher for particles produced using cashew gum and reached 15 g/100 g and 85 g/100 g, respectively. Analyzing the thermogravimetric curves, it was found that cashew gum bulk showed two steps of degradation. For the microcapsules containing encapsulated fish oil in cashew gum, an extra degradation step at 471 °C was found. It was possible to verify the occurrence of diffused and wide peaks in the X-ray diffractograms for all three carbohydrate polymers. The particles produced presented spherical shape with cavities. The fatty acid profile for the fish oil changed only when using modified starch as wall material, where a significant loss of omega-3 fatty acids was observed. The particles produced with cashew gum had physical properties similar to those when applying materials commonly used and this biopolymer has the potential for application as a carrier in spray drying processes .


Andreia Fonseca de Faria, Ana Carolina de Moraes, Patricia Fernanda Andrade, Maria do Carmo Gonçalves & Oswaldo Luiz Alves
Publicado por Cellulose, 02/2017

Bacterial adhesion and consequent biofilm formation are one the biggest hurdles in membrane-based technologies. Due to numerous problems associated with bacterial colonization on membrane surfaces, the development of new approaches to prevent microbial growth has been encouraged. Graphene oxide, produced by the chemical exfoliation of graphite, is a highly water-dispersible nanomaterial which has been used as a platform for the anchoring of nanoparticles and bioactive molecules. In this present study, we propose the fabrication of antimicrobial membranes through the incorporation of grapheme oxide-silver nanocomposites into a cellulose acetate polymeric matrix. Transmission electron microscopy, Raman, and UV–visible diffuse reflectance spectroscopy measurements confirmed the presence of graphene oxide-silver sheets in the modified membranes. In comparison to pristine membranes, membranes containing graphene oxide-silver nanocomposites showed larger surface pores and increased pure water flux. In addition, membranes embedded with graphene oxide-silver presented strong antibacterial activity, being able to inactivate adhered bacteria at a rate of 90% compared to pristine cellulose acetate membranes. Our results strongly suggest that the incorporation of graphene oxide-silver nanocomposites to cellulose acetate is a promising strategy to produce membranes that are able to minimize bacterial attachment and growth.


Silvana da Silva Valter, Carlos Alberto Rodrigues Costa, Liliane Cristina Battirola, Marcelo Alexandre de Farias, Fernando Galembeck & Maria do Carmo Gonçalves
Publicado por Journal of Polymer Research, 02/2017

The aim of this work was to investigate the polymorphic transformation morphology of isotactic poly(1-butene) (iPB-1) in blends with poly (propylene-co-1-butene-co-ethylene) (terPP). The blends were prepared by solution casting followed by compression-molding and were examined immediately after preparation as well as after aging for over 30 days. Morphological changes were firstly observed by polarized optical microscopy, which showed that the terPP promotes the reduction of the spherulite mean size during the crystallization of iPB-1 from the melt. Digital pulsed force microscopy provided data about the terPP interspersion between the interfibrilar and spherulitic regions of the iPB-1 crystals, causing iPB-1 spherulite deformation. However, a better distribution of the amorphous component on the iPB-1 crystals was observed after phase II to I transition, favored by the rearrangement of iPB-1 lamellae and lamellar stacks during phase transition.


Laura C. E. da Silva, Bruna A. Más, Eliana A. R. Duek, Richard Landers, Celso Aparecido Bertran & Maria do Carmo Gonçalves
Publicado por Langmuir, 03/2017

Poly(ε-caprolactone) (PCL) is an aliphatic polyester widely explored in the preparation of guided bone regeneration (GBR) membranes because of its interesting mechanical properties and biodegradability. However, PCL high hydrophobicity often impairs cell adhesion and proliferation as well as calcium phosphate growth, all of which are crucial to achieving suitable bone–tissue integration. In this work, aimed at achieving less-hydrophobic surfaces, amphiphilic molecules were added at low concentrations to the polymeric dope solutions that generated the GBR membranes. During membrane formation, these molecules migrate to the solution/air interface in such a way that, upon liquid–solid phase transition, the negatively charged heads are exposed while the apolar tails are anchored to the polymer bulk. As a consequence, these molecules became nucleating agents for subsequent calcium phosphate growth using an alternating soaking process. Herein, PCL porous membranes containing different amphiphilic molecules, such as stearic acid and bis(2-ethylhexyl) phosphate, were investigated. This new, simple, and atoxic method to superficially treat polymeric membranes could be extended to a wide range of polymers and applications.


Aline Evangelista Aguiar, Mariana de Oliveira Silva, Bianca Cheregatti Longo, Maria do Carmo Gonçalves & Celso Aparecido Bertran
Publicado por JSM Regenerative Medicine & Bioengineering, 09/2017

Scaffold porosity is an essential factor for tissue growth since it allows cell proliferation and vascularization. In this work, three different scaffolds were produced by easy methods. The first one was prepared using Bioglass 45S5 particles and H2O2 as a foaming agent. In the second, glass nanoparticles were arranged as porous structure by the self-assembling of cellulose nanocrystals. In the last, a polymeric xanthan/chitosan composite scaffold was prepared by swelling method. The results showed that the scaffolds presented pore morphology, wall thickness and size distribution that are dependent on the materials and preparation method used, and that they are suitable for a range of applications.


Liliane C. Battirola, Patrticia F. Andrade, Gabriela V. Marson, Miriam D. Hubinger & Maria do Carmo Gonçalves
Publicado por Cellulose, 10/2017

Asymmetric membranes based on cellulose acetate (CA) and cellulose nanofibers (CNF) were prepared by non-solvent induced phase separation. The effect of CNF addition on the morphology, water flux and filtration performance of the CA membranes was investigated. Field emission scanning electron micrographs showed the formation of large macrovoids at low CNF content, while the increase of the CNF content resulted in a sponge-like morphology due to changes in the demixing process rate during membrane formation. Porosity and pure water flux increased with the increment of CNF content. In addition to this, molecular weight cut-off was 200 kg mol−1 for nearly all composite membranes studied. CA/CNF5 composite membranes were also tested to clarify strawberry and raspberry juices as well as whey. Clarification of fruit juices and whey was shown by the decrease of turbidity and solid content. Moreover, the maintenance of antioxidant capacity, as well as overall color for strawberry and raspberry juices, could be seen leading to the conclusion that this composite membrane can be useful in juice production.


Carolina F. Mattos, Fernando Galembeck e Aldo J. G. Zarbin
Publicado por Journal of the Brazilian Chemical Society, 2017

This work describes the preparation, characterization and properties study of multifunctional nanocomposites between poly(styrene-co-butyl acrylate) latex and different carbon nanostructures: iron-filled carbon nanotubes (CNT), graphene or graphene oxide. Different approaches were employed to prepare stable aqueous dispersions of these nanostructures, according to the specificity of each nanomaterial. The nanocomposites were characterized by Raman and Fourier transform infrared (FTIR) spectroscopy, as well as by scanning probe microscopy (SPM) at different modes, providing information regarding the nature of the interaction between the carbon nanostructures and the polymeric matrix. The synergistic effect between the components results in improved mechanical, electrical, thermal and chemical properties of the nanocomposites, when compared to the neat polymer. In addition, the iron species into CNT cavities provide an interesting and unusual magnetic property of the nanocomposites. Results show that the properties of the nanocomposites can be modulated aiming desired application by simply selecting the amount and/or the kind of carbon nanostructure. This work provides information on the features of the three systems used, showing the range of properties that can be covered by using the three nano-fillers.

Antimicrobial activity of the colloids with different size and shapes of silver nanoparticles against Streptococcus mutans

Valdeci Elias Dos Santos Junior, Andrea Gadelha Ribeiro Targino, Miguel Angel Pelagio Flores, Joás Araújo Teixeira, Mônica Vilela Heimer, Hilzethe De Luna Freire Pessoa, André Galembeck, Aronita Rosenblatt, Joan Manuel Rodríguez-Díaz
Publicado por Research on Chemical Intermediates, 05/2017

Silver nanoparticles stabilized with chitosan biopolymer are a new antibacterial agent for treatment of caries. To determine whether the size and morphology of silver nanoparticles in colloidal solution altered their antimicrobial activity, four colored colloids were characterized by ultraviolet–visible (UV–Vis) spectroscopy and transmission electron microscopy (TEM), and their antimicrobial activity [minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)] against reference stocks of Streptococcus mutans ATCC 25175 compared with chlorhexidine and silver diamine fluoride as controls. TEM revealed that the seed solution (SS) contained only spherical nanoparticles with size of 8.7 ± 3.1 nm whereas the other colloids had predominantly spherical nanoparticle shape, although colloid 1 (S1) contained 2.5% triangular nanoparticles. Colloid 2 (S2) had 15.9% triangular and 6.8% cylindrical nanoparticles, while 23.3% of the silver nanoparticles in colloid 3 (S3) were triangular and 1.5% were cylindrical. All the silver nanoparticle colloids showed antimicrobial activity with no statistically significant differences (p > 0.05) in MIC or MBC. The colloids showed antimicrobial activity higher than silver diamine fluoride (p < 0.05) and equivalent to chlorhexidine (p > 0.05). The size and shape of the nanoparticles did not affect the antimicrobial properties of the colored colloids. Thus, the antimicrobial activity of the colloids containing silver nanoparticles against Streptococcus mutans was considered equivalent to that of chlorhexidine, the gold-standard antibiotic in dentistry.

Potentiometric perchlorate determination at nanomolar concentrations in vegetables

Dilmo M.S. Leoterio, Ana Paula S. Paima, Mônica F.Belian, André Galembeck, André F.Lavorante, Edgar Pinto, Célia G. Amorim, Alberto N. Araújo and Maria C.B.S.M. Montenegro
Publicado por Food Chemistry, 07/2017

In this work, an expeditious method based on the multi-commutated flow-analysis concept with poten-tiometric detection is proposed to perform determinations of the emergent contaminant perchlorate invegetable matrices down to nanomolar concentration. To accomplish the task, a tubular shaped potentio-metric sensor selective to perchlorate ion was constructed with a PVC membrane containing 12 mmol/kgof the polyamine bisnaphthalimidopropyl-4,40-diaminodiphenylmethane and 2-nitrophenyl phenyl ether68% (w/w) as plasticizer casted on a conductive epoxy resin. Under optimal flow conditions, the sensorresponded linearly in the concentration range of 6.3107–1.0103mol/L perchlorate. In order toextend the determinations to lower concentrations (4.6(±1.3)1010mol/L perchlorate), a columnpacked with 70 mg of sodium 2,5,8,11,14-pentaoxa-1-silacyclotetradecane-polymer was coupled to theflow-system thus enabling prior pre-concentration of the perchlorate. The proposed procedure providesa simpler alternative for the determination of perchlorate in foods, nowadays only allowed by sophisti-cated and expensive equipment and laborious methods.

AgNPs: The New Allies Against S. Mutans Biofilm - A Pilot Clinical Trial and Microbiological Assay

Priscila L.L. Freire, Allan J.R. Albuquerque, Fabio C. Sampaio, André Galembeck, Miguel A. P. Flores, Thayza C. M. Stamford, Aronita Rosenblatt
Publicado por Brazilian Dental Journal, 07/2017

O objetivo do presente estudo foi avaliar as propriedades antimicrobianas de uma nova formulação composta por nanopartículas de prata, denominada nano silver fluoride (NSF), na inibição de biofilme de Streptococcus mutans sobre a superfície do esmalte dentário de crianças. Variações no pH do biofilme dental e nos valores do índice de Higiene Oral Simplificada (IHO-S) também foram avaliadas após o tratamento com NSF. Trata-se de um estudo piloto, randomizado, duplo cego, cruzado e prospectivo. A amostra foi composta por 12 crianças, de ambos os gêneros, com idades entre 7 e 8 anos, as quais utilizaram as duas soluções testes, S1- NSF e S2- controle negativo (solução salina). O biofilme dental tratado com NSF apresentou menores valores de viabilidade de S. mutans (absorbância) e de unidades formadoras de colônias (UFC) do que o biofilme baseline e o biofilme tratado com S2. Houve diferença estatisticamente significativa entre os valores médios de IHO-S dos grupos baseline e S1, com uma redução dos valores. Não houve qualquer variação nos valores de pH do biofilme dental, antes e depois do tratamento com S1 e S2 e entre os diferentes grupos. Estas propriedades sugerem que NSF possui efeito bactericida sobre o biofilme de S. mutans, podendo ser utilizado clinicamente para o controle e prevenção da formação do biofilme dentário.

Silver nanoparticles in dentistry

Victor T. Noronha, Amauri J.Paula, Gabriela Durán, Andre Galembeck, Karina Cogo-Müller, Michelle Franz-Montan, Nelson Durán
Publicado por Dental Materials, 10/2017

Silver nanoparticles (AgNPs) have been extensively studied for their antimicrobial properties, which provide an extensive applicability in dentistry. Because of this increasing interest in AgNPs, the objective of this paper was to review their use in nanocomposites; implant coatings; pre-formulation with antimicrobial activity against cariogenic pathogens, periodontal biofilm, fungal pathogens and endodontic bacteria; and other applications such as treatment of oral cancer and local anesthesia. Recent achievements in the study of the mechanism of action and the most important toxicological aspects are also presented. Systematic searches were carried out in Web of Science (ISI), Google, PubMed, SciFinder and EspaceNet databases with the keywords “silver nano* or AgNP*” and “dentist* or dental* or odontol. A total of 155 peer-reviewed articles were reviewed. Most of them were published in the period of 2012–2017, demonstrating that this topic currently represents an important trend in dentistry research. In vitro studies reveal the excellent antimicrobial activity of AgNPs when associated with dental materials such as nanocomposites, acrylic resins, resin co-monomers, adhesives, intracanal medication, and implant coatings. Moreover, AgNPs were demonstrated to be interesting tools in the treatment of oral cancers due to their antitumor properties. The literature indicates that AgNPs are a promising system with important features such as antimicrobial, anti-inflammatory and antitumor activity, and a potential carrier in sustained drug delivery. However, there are some aspects of the mechanisms of action of AgNPs, and some important toxicological aspects arising from the use of this system that must be completely elucidated.

Importance of the hierarchical core@multi-shell nanostructure in obtaining white light emission in Ln(III)-doped ZrO2 nanoparticles

Cristine Santos de Oliveira, Jefferson Bettini, Fernando Aparecido Sigoli and Italo Odone Mazali
Publicado por Crystal Growth & Design, 09/2017

The design of the hierarchically tailored 4.4 nm nanoparticles was based on the alternation between undoped and Ln(III)-doped layers (Ln(III) = Eu(III), Tb(III)), ensuring the isolation of different Ln(III) ions in order to prevent energy transfers between them, which may lead to long-term loss of quality of the emission due to one-sided cascading of the excitation energy to a single emitter. Photoluminescence emission and excitation spectra have shown the importance of this design in obtaining white light: for the alternating layer design there is no energy transfer between Tb(III) and Eu(III) ions, and emission spectra with λexc = 260 nm of Tb(III),Eu(III)-codoped ZrO2 nanoparticles over a ZnO-coated silica host show a combination of Tb(III) green, Eu(III) red, and silica defect blue emissions resulting in pure white emission, and warm white with an additional Eu(III)-doped layer. While the ZnO coating layer was vital in improving Eu(III) emission intensity by suppression of SiO2 surface (−OH) oscillators, nanoparticles constructed with gradually fewer features of the main hierarchical nanostructure resulted in Tb(III) → Eu(III) energy transfers, and loss of fine control over the final emission color.

Supramolecular Approach to Decorate Multi-Walled Carbon Nanotubes with Negatively Charged Iron(II) Complexes

Sergio A. V. Jannuzzi, Bianca Martins, Luis E. S. C. Huamanía and André L. B. Formiga
Publicado por Journal of the Brazilian Chemical Society, 2017

Poly(4-vinylpyridine) (P4VP) and P4VP/pentacyanoferrate(II) metallopolymer were used to suspend up to 1 mg mL-1 of multi-walled carbon nanotubes (MWCNT) in ethanol/water mixtures, providing noncolavent decoration of MWCNT with electroactive iron complex. The major interaction between polymer side chains and nanotubes is via π-π stacking, rather than charge-transfer interaction reported for many nitrogenated interacting molecules. Preservation of structural integrity of the nanotubes after functionalization was attested by Raman, which was reflected in the semiconducting character of the dried nanocomposites. Proximity of pentacyanoferrate(II) to MWCNT walls was suggested by its solvatochromic shift of metal-to-ligand charge transfer band attributed to [Fe(CN)5]3− bound to P4VP pyridyl moieties. Electronic microscopy revealed smooth films and good adhesion between MWCNT bundles and the matrix. The procedure described herein can be used to combine unique properties of transition metal compounds able to coordinate to pyridyl groups, with the film-forming ability of P4VP and conductivity provided by MWCNT.

Antimicrobial activity of Melaleuca alternifolia nanoparticles in polymicrobial biofilm in situ

Márcia Ebling de Souza, Dariane Jornada Clerici, Camila Marina Verdi, Gabriela Fleck, Priscilla Maciel Quatrin, Luana Ebling Spat, Pauline Cordenonsi Bonez, Camilla Fillippi dos Santos, Raquel Pippi Antoniazzi, Fabrício Batistin Zanatta, André Gundel, Diego Stefani Teodoro Martinez, Rodrigo de Almeida Vaucher and Roberto Christ Vianna Santos
Publicado por Microbial Pathogenesis, 2017

Microbial biofilms represent a challenge in the treatment of infections, due to the low efficacy of the antimicrobials. This study evaluated the antimicrobial effect of nanoparticles of Melaleuca alternifolia (TTO) in dental biofilm. Thirty-eight volunteers used an oral device in situ in situ including four bovine enamel specimens for 07 days. From the fifth day four solutions were applied randomly for each specimen: Physiological Saline Solution (0.85% NaCl) (C+), Chlorhexidine 0.12% (CHX), M. alternifolia oil 0.3% (TTO), and a nanoparticle solution of 0.3% M. alternifolia oil (NPTTO). The nanoparticles of TTO were characterized for pH, IPD, medium size, zeta potential and Transmission Electron Microscopy. Antimicrobial activity was evaluated by viable microorganisms count and the structure of the biofilm by atomic force microscopy. The NPTTO presented pH 6.4, particle diameter of 197.9 ± 1 nm, polydispersion index of 0.242 ± 0.005, zeta potential of -7.12 mV and ±0:27 spherical shape. The C+ resulted in 100% of bacterial vitality, while CHX, TTO and NPTTO showed 34.2%, 51.4% and 25.8%, respectively. The AFM images showed biofilms with an average roughness of 350 nm for C+, 275 nm for CHX, 500 nm for TTO and 100 nm for NPTTO. The NPTTO demonstrated excellent antimicrobial activity in the biofilm formed in situ and will possibly be used in future for the treatment/prevention of oral biofilms.

Melaleuca alternifolia nanoparticles against Candida species biofilms

M.E. Souza, L.Q.S. Lopes, P.C. Bonez, A. Gündel, D.S.T. Martinez, M.R. Sagrillo, J.L. Giongo, R.A. Vaucher, R.P. Raffin, A.A. Boligon, R.C.V. Santos
Publicado por Microbial Pathogenesis, 2017

Candida infection is an important cause of morbidity and mortality on immunosuppressed patients. This growing trend has been associated with resistance to the antimicrobial therapy and the ability of microorganism to form biofilms. TTO oil is used as antimicrobial which shows antibiofilm activity against Candida species. However, it presents problems due to its poor solubility and high volatility. The present study aimed to evaluate in vitro antibiofilm activity of TTO nanoparticles against many Candida species. It was performed the characterization of the oil and nanoparticles. The levels of exopolysaccharides, proteins, and the biomass of biofilms were measured. The chromatographic profile demonstrated that the TTO oil is in accordance with ISO 4730 with major constituents of 41.9% Terpinen-4-ol, 20.1% of γ-Terpinene, 9,8% of α-Terpinene, and 6,0% of 1,8-Cineole. The TTO nanoparticles showed pH of 6.3, mean diameter of 158.2 ± 2 nm, polydispersion index of 0.213 ± 0.017, and zeta potential of −8.69 ± 0.80 mV. The addition of TTO and its nanoparticles represented a significant reduction of biofilm formed by all Candida species, as well as a reduction of proteins and exopolysaccharides levels. It was possible to visualize the reduction of biofilm in presence of TTO nanoparticles by Calcofluor White method.

Nanopharmaceuticals as a solution to neglected diseases: Is it possible?

German A. Islan, Marcela Durán, Maximiliano L. Cacicedo, Gerson Nakazato, Renata K.T. Kobayashi, Diego S.T. Martinez, Guillermo R. Castro, Nelson Durán
Publicado por Acta tropica, 2017

The study of neglected diseases has not received much attention, especially from public and private institutions over the last years, in terms of strong support for developing treatment for these diseases. Support in the form of substantial amounts of private and public investment is greatly needed in this area. Due to the lack of novel drugs for these diseases, nanobiotechnology has appeared as an important new breakthrough for the treatment of neglected diseases. Recently, very few reviews focusing on filiarasis, leishmaniasis, leprosy, malaria, onchocerciasis, schistosomiasis, trypanosomiasis, and tuberculosis, and dengue virus have been published. New developments in nanocarriers have made promising advances in the treatment of several kinds of diseases with less toxicity, high efficacy and improved bioavailability of drugs with extended release and fewer applications. This review deals with the current status of nanobiotechnology in the treatment of neglected diseases and highlights how it provides key tools for exploring new perspectives in the treatment of a wide range of diseases.

Nanotoxicity of graphene oxide: Assessing the influence of oxidation debris in the presence of humic acid

Zaira Clemente, Vera Lúcia S. S. Castro, Lidiane S. Franqui, Cristiane A. Silva, Diego Stéfani T. Martinez
Publicado por Environmental Pollution, 2017

This study sought to evaluate the toxicological effects of graphene oxide (GO) through tests with Danio rerio (zebrafish) embryos, considering the influence of the base washing treatment and the interaction with natural organic matter (i.e., humic acid, HA). A commercial sample of GO was refluxed with NaOH to remove oxidation debris (OD) byproducts, which resulted in a base washed GO sample (bw-GO). This process decreased the total oxygenated groups in bw-GO and its stability in water compared to GO. When tested in the presence of HA, both GO and bw-GO stabilities were enhanced in water. Although the embryo exposure showed no acute toxicity or malformation, the larvae exposed to GO showed a reduction in their overall length and acetylcholinesterase activity. In the presence of HA, GO also inhibited acid phosphatase activity. Our findings indicate a mitigation of material toxicity after OD removal. The difference in the biological effects may be related to the materials’ bioavailability and biophysicochemical interactions. This study reports for the first time the critical influence of OD on the GO material biological reactivity and HA interaction, providing new data for nanomaterial environmental risk assessment and sustainable nanotechnology.

Structural aspects of graphitic carbon modified SBA-15 mesoporous silica and biological interactions with red blood cells and plasma proteins

Diego S. T. Martinez, João Paulo V. Damasceno, Lidiane S. Franquia, Jefferson Bettini, Italo O. Mazali, Mathias Strauss
Publicado por Materials Science and Engineering: C, 2017

Functional mesoporous materials have been worldwide studied for different applications. Mesoporous silicas are highlighted due to the synthetic possibilities for the preparation of such materials with different particle sizes and morphologies, and controlled pores sizes and structures. Moreover, the silica superficial silanol groups are explored in several chemical modifications, leading to functional materials with tuned functionalities and properties. In this work, an organo-functionalization and pyrolysis synthetic procedure is used to obtain graphitic carbon modified mesoporous SBA-15 silica. The carbon content was tuned during the functionalization step, and the graphitic nanodomains were formed in the pores surface and particles outer surface. Textural and small angle X-ray diffraction analysis accessed the presence of the carbon nanostructures inside the SBA-15 mesopores. Advanced microanalysis using electron energy loss spectroscopy coupled to a transmission electron microscope had confirmed the carbon distribution along the silica pores, which gives higher hydrophobicity and changed the interaction of the mesoporous material with biological systems. Finally, the influence of the surface modification with graphitic carbon species over the interaction with human red blood cells (hemolysis) and human blood plasma (protein corona formation) was elucidated for the very first time for this kind of functional materials. It was observed that the graphitic carbon species considerably reduced the hemolytic effect of the silica particles, and was responsible for modulating the loading and composition of the hard corona plasma proteins. This work deepness the fundamental knowledge on the interaction between such nanomaterials and biological systems, one step further the use of these modified silicas in biomedical applications.

Nanothermometer based on intensity variation and emission lifetime of europium(III) benzoylacetonate complex

Diego A. Gálico, Italo O. Mazali and Fernando A. Sigoli
Publicado por Journal of Luminescence, 2017

Temperature dependence of the photophysical properties of europium(III) complex with the benzoylcetonate ligand were evaluated. The photostability of the complex and the temperature dependence of the 5D07F2 transition band area (maximum relative sensitivity of 5.25% K−1 at 303 K) makes this complex promising as temperature probe. The temperature dependence of the 5D07F2 transition band indicates that the electron-phonon coupling is probably the main mechanism operating in the temperature dependence of the photophysical properties of the complex.

An inquiry-based freshman biochemistry lab set to enhance students' autonomy

Thanuci Silva and Eduardo Galembeck
Publicado por Química Nova, 2017

Inquiry-based laboratory sessions are recognized for contributing to enhancing students' autonomy and they were used in the reorganization of the Biochemistry laboratory offered to freshman Biology students in this university. Students were previously asked to follow rigid laboratory protocols attempting to achieve the correct results of their experiments. The inquiry-based activities were designed to develop students autonomy to plan and to perform experiments, as well as communicating and discussing their results. The inquiry-based and autonomy approach followed is classified in the literature as Organizational, Procedural, and Cognitive. The levels of autonomy required from students were increased sequentially. The first activity was the least demanding, since the students received detailed instructions from the worksheet. The activities became gradually more complex, transferring to students most decisions on setting up and performing the experiments. Student skill improvement was obtained, as verified by excerpts from student reports, by data obtained from content analysis of the exams, and scientific report scores indicate that this approach may have stimulated the improvement of several skills related to different autonomy aspects. Most important, students showed increased ownership of the laboratory materials, reagents, laboratory environment and especially of learning, showing a sense of active participation in the experimental activities.

Novel study guides for biochemistry meaningful learning in biology: a design-based research

Caetano da Costa and Eduardo Galembeck
Publicado por Journal of Biochemistry Education, 2017

Para lidar com a transmissão em geral descontextualizada da informação no ensino de bioquímica, foram aplicadas três intervenções na disciplina Metabolismo para Biologia, na forma de estudos dirigidos inovadores. Descrevem-se a construção, aplicação e avaliação de dois estudos dirigidos, contextualizados como um problema real ou uma visão integrativa, usando temas amplos como evolução e adaptação metabólica. A fim de avaliar o impacto de ambas as intervenções sobre o interesse, motivação e aprendizagem das vias metabólicas, foi realizada uma pesquisa baseada em design com ciclos de aplicação e avaliação, por meio de observação em sala de aula, análise de notas em provas e entrevistas com estudantes. A análise e a interpretação dos resultados indicam benefícios para o ensino e a aprendizagem, com informações úteis para orientar a elaboração e o refino de novos materiais de ensino e para tornar a aprendizagem ativa mais significativa.

Using augmented reality to teach and learn biochemistry

Juan Carlos Vega Garzón, Marcio Luiz Magrini and Eduardo Galembeck
Publicado por Biochemistry and Molecular Biology Education, 2017

Understanding metabolism and metabolic pathways constitutes one of the central aims for students of biological sciences. Learning metabolic pathways should be focused on the understanding of general concepts and core principles. New technologies such Augmented Reality (AR) have shown potential to improve assimilation of biochemistry abstract concepts because students can manipulate 3D molecules in real time. Here we describe an application named Augmented Reality Metabolic Pathways (ARMET), which allowed students to visualize the 3D molecular structure of substrates and products, thus perceiving changes in each molecule. The structural modification of molecules shows students the flow and exchange of compounds and energy through metabolism.

Developing and Supporting Students’ Autonomy To Plan, Perform, and Interpret Inquiry-Based Biochemistry Experiments

Thanuci Silva and Eduardo Galembeck
Publicado por Journal of Chemical Education, 2017

Laboratory sessions are designed to develop the experimental skills and the acquaintance with instruments that may contribute to a successful career in Biochemistry and associated fields. This study is a report on improving a traditional Biochemistry course by devising the laboratory sessions as an inquiry-based environment to develop the students’ autonomy to plan, perform, and interpret experiments. We reformulated our Biochemistry laboratory to have three activities that sequentially increase regarding autonomy. We used an autonomy support structure consisting of varying levels of engagement by the student in such aspects as Organizational, Procedural, and Cognitive, gradually transferring to students the responsibility for their decisions within the laboratory. Our results show that students performed better on the less instructed worksheet activities, characterized by a more complex autonomy support, as compared to the activities tightly controlled by worksheet directions. A review of the group lab reports suggests that students showed skills required to work with different levels of autonomy. Thus, this approach has positively supported the students’ autonomy, not only mapping their progress through the activities proposed but also encouraging them to make decisions during their experiments and stimulating their ability to think and to plan experiments themselves.

Proof of concept for a passive sampler for monitoring of gaseous elemental mercury in artisanal gold mining

Elias de Barros Santos, Paleah Moher, Stacy Ferlin, Anne Hélène Fostier, Italo Odone Mazali, Kevin Telmer and Alexandre Guimarães Brolo
Publicado por Scientific Reports, 2017

Mercury emissions from artisanal gold mining operations occurring in roughly 80 developing countries are a major workplace health hazard for millions of people as well as the largest contributor to global mercury pollution. There are no portable, cheap, and rapid methods able to inform workers or health practitioners of mercury exposure on site in remote locations. In this work, a proof of concept for a miniaturized mercury sampler, prepared by the direct reduction of gold into the porous nanostructures of Vycor glass (PVG), is introduced. Mercury retention on the PVG/Au sampler induces significant color changes, due to the formation of Au-Hg amalgam that affects the surface plasmon resonance characteristics of the material. The color change can potentially be quantified by the analysis of pictures obtained with a cell phone camera rapidly and onsite. Laboratory experiments showed the viability of using PVG/Au as passive sampler for monitoring of Hg°. PVG/Au samplers were then deployed in an artisanal and small-scale gold mining (ASGM) operations in Burkina Faso and it was able to indicate personal mercury exposures. The amount of mercury quantified in the samplers for all miners was higher than the current personal exposure limit set by the US Occupational Safety & Health Administration (OSHA).

Using Gold Nanoparticles as Passive Sampler for Indoor Monitoring of Gaseous Elemental Mercury

Elias de Barros Santos, Stacy Ferlin, Anne Hélène Fostier and Italo Odone Mazali
Publicado por Journal of the Brazilian Chemical Society, 2017

This study reports a functional passive sampler for monitoring gaseous elemental mercury (GEM). The material consists of gold nanoparticles (AuNP) deposited forming a film on thiol-modified glass slides. AuNP colloid was synthesized using sodium citrate, resulting in a size of 24.2 ± 0.8 nm, as determined by transmission electron microscopy analysis. For the indoor test, AuNP films were placed into Petri plates. One part of the lot was kept exposed to the laboratory's atmosphere and the other part was stored in closed plate (control). The films were removed from both plates along a month and analyzed using a direct mercury analyzer. A linear relationship between Hg retention and exposure time was obtained until the 23rd day, which allowed to calculate a GEM retention rate of 2.2 ng g-1 day-1; the maximum retention capacity was around 50 ng g-1. This study provides an efficient method for indoor monitoring of GEM using AuNP films as passive sampler.

Understanding the clay-PEG (and hydrophobic derivatives) interactions and their effect on clay hydration and dispersion: A comparative study

Santiago Villabona-Estupiñán, Jorge de Almeida Rodrigues, Regina Sandra Veiga Nascimento
Publicado por Applied Clay Science, 2017

In oil and gas well drilling, the effective minimization of clay-water interactions is an essential function that water-based drilling fluids must meet in order to maintain the integrity of the shale formations as well as suitable rheological properties. In this work, the protective effect of poly(ethylene glycol) 2000 (PEG2000) and two hydrophobic derivatives on the hydration and dispersion of reactive clay materials was investigated. Thus, conventional inhibition tests were combined with adsorption measurements and analyses by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetry (TGA) in an attempt to establish structure-performance relationships. It was found that both PEG2000 and its hydrophobic derivatives can strongly adsorb, in equimolar amounts, on mineral clay following a Langmuir type behavior, in which bilayers are formed in the clay interlayer region at surface saturation. It was found that the PEG backbone rules the adsorption process, while the hydrocarbon tails of the hydrophobically modified products do not play a decisive role. However, it was verified that hydrocarbon tails play a central role in the mechanism of inhibition of clay particles hydration. Bentonite inhibition test revealed that the incorporation of two hydrocarbon tails at the PEG2000 chain ends duplicate the performance of oligomer, regarding the product with just one tail.

Laser beam backscattering as a new tool to study the effect of inhibitors on shale particles-water interactions: A real-time analysis

Vinicius Kartnaller, Conny Cerai Ferreira, Santiago Villabona-Estupiñán, Elizabeth Roditi Lachter, Jorge de Almeida Rodrigues Junior, Regina Sandra Veiga Nascimento, João Cajaiba
Publicado por Applied Clay Science, 2017

The interaction between clay-rich shales formations and water is one of the most relevant factors for well instability in drilling operations, representing a significant challenge for the oil and gas industry. To minimize the problems related to water sensitivity, chemical additives or inhibitors are incorporated into water-based drilling fluids, acting over the water-shale interactions and maintaining the integrity of the sedimentary rock. In this work a novel approach is proposed to gain new information about the dynamics of the inhibitory process and to evaluate the shale inhibition efficiency of different chemical additives using a laser beam backscattering technique. This technique is based on the analysis of laser backscattering profiles promoted by dispersed particles in a suspension, which results in a particle chord length distribution (CLD). The technique was adequate for monitoring the consequences of the interactions between water and shales, differentiating its reactivities by monitoring the effect of different inhibitors on each system's CLD over time. Two cationic inhibitors (KCl and PDADMAC, a cationic polymer) were tested, and the obtained results showed that the inhibition phenomenon is more than the inhibitor itself, and it depends on the shale structure and the capability of the inhibitor to interact with its clay stacks. A methodology was also developed to calculate an inhibition efficiency score (IES), in which the technique's real-time factor enables it to estimate how much better an inhibitor is when compared to others over time. Among the evaluated systems, the inhibitor that achieved the biggest efficiency for shale was KCl, resulting in 69%.

Glow-wire evaluation of polymeric materials for the electric sector: Effect of the interlayer spacing of montmorillonite

Simone Pereira da Silva Ribeiro, Luciana Rocha de Moura Estevão, Regina Sandra Veiga Nascimento
Publicado por Applied Clay Science, 2017

In this study the glow-wire technique was used in the evaluation of synergistic effects between organophilic montmorillonites with different basal spacings and an intumescent formulation containing ammonium polyphosphate (APP) and pentaerythritol (PER) in a poly (ethylene-co-butyl acrylate), EBA 30, polymeric matrix. The flammability of the samples was also evaluated through limiting oxygen index (LOI) analyses, UL-94 standard rating and heating microscopy. The morphology of the samples was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). These analyses revealed that processing in a twin screw extruder led to the formation of intercalated and exfoliated nanocomposites. The influence of processing via internal mixer and twin-screw extruder was also evaluated. Glow-wire tests revealed that the addition of montmorillonites with smaller basal spacings led to a synergistic effect with the intumescent formulation, an effect which was not observed when using montmorillonites with basal spacings larger than 30 Å. The intumescent materials containing montmorillonites with smaller basal spacings showed GWFI (glow-wire flammability index) as high as 960 °C, which indicates that they could be used in the electrical area.

Multifunctional Hybrid Aerogels: Hyperbranched Polymer-Trapped Mesoporous Silica Nanoparticles for Sustained and Prolonged Drug Release

Heveline D. M. Follmann, Osvaldo N. Oliveira Jr, Danielle Lazarin-Bidóia, Celso V. Nakamura, Xiaoxi Huang, Tewodros Asefa and Rafael Silva
Publicado por Nanoscale, 2017

In this study, we show the synthesis of novel hybrid organic–inorganic aerogel materials with one-dimensionally aligned pores and demonstrate their use as sustained and prolonged release systems for a hydrophobic drug. The materials are synthesized by trapping mesoporous silica nanoparticles within a hyperbranched polymer network made from poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The synthetic method involves dispersing mesoporous silica nanoparticles in a polymer solution, then freeze-drying the solution, and finally subjecting the resulting materials to high temperature to activate a solid-state condensation reaction between PVA and PAA. Before trapping the mesoporous silica nanoparticles within the hyperbranched polymeric network, their pores are decorated with hydrophobic groups so that they can serve as good host materials for hydrophobic drugs. The potential application of the hybrid aerogels as drug carriers is demonstrated using the hydrophobic, anti-inflammatory agent dexamethasone (DEX) as a model drug. Due to their hydrophobic pores, the hybrid aerogels show excellent drug loading capacity for DEX, with an encapsulation efficiency higher than 75%. Furthermore, the release pattern of the payloads of DEX encapsulated in the aerogels is highly tailorable (i.e., it can be made faster or slower, as needed) simply by varying the PVA-to-PAA weight ratio in the precursors, and thus the 3-dimensional (3-D) structures of the cross-linked polymers in them. The materials also show sustained drug release, for over 50 days or more. In addition, the aerogels are biocompatible, as demonstrated with Vero cells, and greatly promote the cell proliferation of L929 fibroblasts. Also, the nanoparticles functionalized with quaternary groups and dispersed within the aerogels display bactericidal activity against E. coli, S. aureus, B. subtilis, and P. aeruginosa. These new hybrid aerogels can, thus, be highly appealing biomaterials for sustained and prolonged drug release, such as wound dressing systems.

Silver nanoparticles biosynthesis and impregnation in cellulose acetate membrane for anti-yeast therapy

Taciana A. Silva, Patrícia F. Andrade, Karen Segala, Larissa S. C. Silva, Larissa P. Silva, Silvia V. G. Nista, Lucia H. I. Mei, Nelson Duran and Maria F. S. Teixeira
Publicado por African Journal of Biotechnology, 2017

Silver nanoparticles (AgNPs) are nanoforms that express higher antimicrobial potential due to their shape and reduced size. The use of fungi to mediate the synthesis of AgNPs has increased the interest of scientists because of their rapid growth, large-scale cultivation and secretion of non-toxic molecules. The aim of this study was to synthesize AgNPs mediated by Aspergillus oryzae DPUA 1624 and evaluate the antimicrobial activity of these molecules incorporated in cellulose acetate nanomembranes (NanoMAC). The synthesis of AgNPs was confirmed by UV-visible spectroscopy and the characterization was performed by dynamic light scattering, transmission electron microscopy, X-ray diffraction, X-ray dispersive energy and advanced spectroscopy and spectroscopy methods. The synthesis of the membrane was done by electro-spinning and its thickness was analyzed in scanning electron microscope. The AgNPs were added to NanoMAC and the antimicrobial effect was evaluated by agar diffusion method against Staphylococcus aureus, Escherichia coli and Candida albicans. The aqueous extract of A. oryzae mediated the synthesis of AgNPs with rounded and some triangular shapes. The diameter and zeta potential of these particles were 61.15±11.45 nm and -28.7 mv, respectively. The NanoMAC with AgNPs showed an increase in antifungal activity of 24.22% when tested against C. albicans. This study demonstrated that A. oryzae is able to mediate AgNP synthesis with anti-yeast action and the impregnation of AgNPs in acetate cellulose nanomembranes resulted in the development of a more efficient antimicrobial nanocomposite.

Silver and Silver Chloride Nanoparticles and their Anti-Tick Activity: a Mini Review

Nelson Durán, Marcela Durán and Celso E. de Souza
Publicado por Journal of the Brazilian Chemical Society, 2017

This overview highlights the importance of characterization of biogenic nanoparticles of silver and silver chloride in order to understand the action on ticks or pathogens transmitted by them. These nanoparticles appear as important active principles in this area. They can act against ticks or against major pathogens transmitted by the bite of ticks such as bacteria, viruses or protozoa with equal or better efficacy of antibiotics, antiviral or antiparasitic agents. Anti-tick activities on Rhipicephalus (Boophilus) microplus, Hyalomma anatolicum, Hyalomma isaaci and Haemaphysalis bispinosa are discussed. Perspectives of these nanoparticles acting on bacteria, viruses and protozoa infections are also discussed

Electrospun poly(ethylene oxide)/chitosan nanofibers with cellulose nanocrystals as support for cell culture of 3T3 fibroblasts

Daniela M. Ridolfi, Ana Paula Lemes, Sheila de Oliveira, Giselle Z. Justo, Marcelly V. Palladino and Nelson Durán
Publicado por Cellulose, 2017

Chitosan/poly(ethylene oxide) (PEO) (5:1) nanofibers with cellulose nanocrystals (CNCs) were produced using an electrospinning technique. The addition of CNCs to the chitosan/PEO solutions allowed the production of uniform fibers (without beads) with a high proportion of chitosan. The fiber diameters were influenced by the concentration of CNCs in the chitosan/PEO solutions. The solutions containing 10% (w/w) of CNCs produced thinner fibers compared to solutions containing 5% (w/w) of CNCs. Thermogravimetric analysis indicated that the nanofibers were thermally stable, despite the CNCs having an effect on the PEO decomposition. Results from the cell assay in cultures of 3T3 fibroblasts indicated that the chitosan/PEO nanofibers (with 10% CNCs) promoted cell attachment with changes in the cytoskeletal organization. The results obtained in this work highlight the favorable effect of CNCs in electrospinning of chitosan/PEO. As expected, the influence of nanofibers on 3T3 fibroblasts F-actin and β-tubulin network revealed alterations in cytoskeleton, leading to changes in cell morphology and spreading

Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

Linping Qian, Zhen Wang, Evgeny V. Beletskiy, Jingyue Liu, Haroldo J. dos Santos, Tiehu Li, Maria do C. Rangel, Mayfair C. Kung and Harold H. Kung
Publicado por Nature Communications, 2017

The ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml−1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s−1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participation in the cycle. Spectroscopic characterization suggests that 7–8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation.

Characterization of PCL and Chitosan Nanoparticles as Carriers of Enoxaparin and Its Antithrombotic Effect in Animal Models of Venous Thrombosis

Lucas Bessa Prado, Stephany Cares Huber, Aline Barnabé, Fernanda Dutra Santiago Bassora, Devanira Souza Paixão, Nelson Duran and Joyce Maria Annichino-Bizzacchi
Publicado por Journal of Nanotechnology, 2017

This study was based on the preparation, characterization, and animal in vivo experiments performed to evaluate nanoparticles of poly(ɛ-caprolactone) (PCL) and chitosan as carriers of enoxaparin. The nanoparticles were characterized and presented satisfactory results in terms of size, polydispersity, and encapsulation efficiency. Anticoagulant activity of the nanoparticles was maintained for 14 hours when the administration was subcutaneous; however no activity was observed after oral administration. There was a significant reduction in thrombus size, in vivo, for both free and encapsulated enoxaparin in comparison with the control group after subcutaneous administration. Oral administration results however were indifferent. In conclusion, the double emulsion method w/o/w was efficient for enoxaparin encapsulation, producing spherical nanoparticles with high encapsulation efficiency. For in vivo studies, the encapsulated enoxaparin showed a sustained anticoagulant activity for a higher period of time compared to free enoxaparin, with an antithrombotic effect when administered subcutaneously.

Design, characterization and in vitro evaluation of linalool-loaded solid lipid nanoparticles as potent tool in cancer therapy

BorisRodenak-Kladniew, German A.Islan, Margarita G. de Bravo, Nelson Durán, Guillermo R. Castro
Publicado por Colloids and Interfaces B: Biointerfaces, 2017

Linalool (LN) is a monoterpene found in essential oils of plants and herbs that produces multiple effects on the mevalonate pathway and interesting antiproliferative activity in cancer cells. However, due to its poor aqueous solubility, an efficient vehicle is needed to improve its administration and bioavailability in physiological media. LN encapsulation in solid lipid nanoparticles (SLN) with different compositions was explored and in vitro tested in two cancer cell lines. SLN of myristyl myristate (MM), cetyl esters (SS) and cetyl palmitate (CP) were prepared by sonication in the presence of Pluronic®F68 as surfactant. Nanoparticle size, morphology and distribution were determined by dynamic light scattering in combination with optical and transmission electron microscopy (TEM). SLN showed spherical shape and mean diameters in the range of 90–130 nm with narrow size dispersion (PDI values lower than 0.2) and Z potentials around −4.0 mV. The encapsulation percentages of LN in SLN were higher than 80% for all tested formulations and exhibited in vitro LN controlled release profiles for at least 72 h. The nanoparticles were physicochemically characterized by FTIR, XRD, DSC and TGA, and the incorporation of LN into SLN was higher than 80% in tested matrices. The developed formulations, and in particular SLN (MM)-LN, showed in vitro antiproliferative effects on hepatocarcinoma (HepG2) and lung adenocarcinoma (A549) cell lines in a dose-dependent response, and higher inhibitory effects were found in comparison with free LN. The cellular uptake of SLN was demonstrated by fluorescence microscopy, enhancing the ability of nanoparticles to intracellularly deliver the cargo molecules.

Development of double emulsion nanoparticles for the encapsulation of bovine serum albumin

Nelida Y. Martinez, Patricia F. Andrade, Nelson Durán and Sebastian Cavalitto
Publicado por Colloids and Interfaces B: Biointerfaces, 2017

In the present work, a double emulsion was developed for the encapsulation of Bovine Serum Albumin (BSA) as a model protein for the future encapsulation of viral proteins. The first emulsion polydispersity index (PDI) was studied with increasing concentrations of poly (ε-caprolactone) (PCL) as stabilizer (from 16% w/v to 5% w/v) and polyvinyl alcohol (PVA) as the surfactant in the second emulsion at 1.5% w/v. Results suggest that at decreasing concentrations of PCL the PDI of the emulsion also decrease, indicating that viscosity of the emulsion is crucial in the homogeneity of the resultant size distribution of the nanoparticles. When PVA concentration in the second emulsion was increased from 1.5% w/v to 2.5% w/v the PDI also increased. To study the relationship between the structure of the surfactant in the second emulsion and the resultant BSA encapsulation, emulsions were prepared with Pluronic F68 and PVA both at 1.5% w/v and PCL in the first emulsion at 5% w/v. Results indicated that Pluronic F68 was a better stabilizer because at the same experimental conditions encapsulation of BSA was 1.5 higher than PVA. FTIR studies confirmed the presence of BSA in the nanoparticles. SEM and TEM microscopies showed a size distribution of 300 nm–500 nm size of nanoparticles. Circular dichroism studies demonstrated that the secondary structure of the protein was conserved after the encapsulation into the nanoparticles.

Nanoscale Structure of Urethane/Urea Elastomeric Films

Dennys Reis, Ana C. Trindade, Maria Helena Godinho, Laura C. Silva, Maria do Carmo Gonçalves and Antônio M. Figueiredo Neto
Publicado por Brazilian Journal of Physics, 2017

The nanostructure of urethane/urea elastomeric membranes was investigated by small-angle X-ray scattering (SAXS) in order to establish relationships between their structure and mechanical properties. The networks were made up of polypropylene oxide (PPO) and polybutadiene (PB) segments. The structural differences were investigated in two types of membranes with the same composition but with different thermal treatment after casting. Type I was cured at 70–80 °C and type II at 20 °C. Both membranes showed similar phase separation by TEM, with nanodomains rich in PB or PPO and 25 nm dimensions. The main difference between type I and type II membranes was found by SAXS. The type I membrane spectra showed, besides a broad band at a 27-nm q value (modulus of the scattering vector), an extra band at 6 nm, which was not observed in the type II membrane. The SAXS spectra were interpreted in terms of PPO, PB soft segments, and urethane/urea links, as well as hard moiety segregation in the reaction medium. This additional segregation (q = 7 nm), although subtle, results in diverse mechanical behavior of in both membranes.

Paving the Way for the Molecular-Level Design of Adsorbents for Carbon Capture: a Quantum-Chemical Investigation of the Adsorption of CO2 and N2 on Pure-Silica Chabazite

Antonio Claudio Pinheiro Barbosa, Pierre Mothé Esteves and Marco Antonio Chaer Nascimento
Publicado por Journal of Physical Chemistry C, 2017

Pure-silica chabazite is a promising material for capturing CO2 from flue gases in adsorption-based carbon capture and storage. The adsorption of CO2 and N2 on pure-silica chabazite has been studied at the molecular level with Density Functional Theory in the finite cluster/supermolecule approach. Molar enthalpies of adsorption of CO2 and N2 have been calculated with excellent agreement (<1.0 kJ/mol) with the experimental values. Additionally, the experimental structural information available in the case of CO2 could be correctly reproduced and even better interpreted. Vibrational frequency shifts for both adsorbate molecules and site-specific information for the case of N2, which are not yet available from experiment, could be anticipated. The results of this work indicate that this type of analysis may pave the way for the development of a new generation of adsorbents, designed at the molecular level, for capturing CO2 from flue gases by adsorptive separation processes.

Methylene blue oxidation over iron oxide supported on activated carbon derived from peanut hulls

Lindaura Almeida da Silva, Sarah Maria Santana Borges, Priscilla Nogueira Paulino, Marco A. Fraga, Sérgio Telles de Oliva, Sérgio Gustavo Marchetti and Maria do Carmo Rangel
Publicado por Catalysis Today, 2017

In order to contribute to the environment preservation, catalysts based on iron oxides supported on activated carbon were prepared from peanut hulls and evaluated in Fenton reaction to remove methylene blue from model wastewaters. The activated carbons were prepared by simultaneous carbonization and activation of peanut hulls with low amounts of sodium hydroxide and then impregnated with iron nitrate solutions to get samples with 5, 7.5,10, 12.5 and 15 wt.% Fe. All solids were microporous and made of hematite and magnetite supported on activated carbon. The amount of magnetite changed with iron content and was related to surface oxidation, producing more oxygenated groups (carboxylic acids, lactones, carboxylic anhydrides and phenols) than activated carbon. Both activated carbons and iron-based catalysts were able to remove methylene blue from aqueous streams by adsorption and oxidation, the activity of activated carbon being assigned to oxygenated groups. For iron oxide-based catalysts, the adsorption capacity was related to the increase of surface oxygenated groups while the oxidation activity was assigned to the amount and crystals size of magnetite, besides the surface oxygenated groups. The association of these properties led to catalysts with close performances, being the catalyst with 10 wt.% Fe slightly more efficient than the others in dye removal. The obtained catalysts produced low amounts of byproducts, being promising to remove dyes in industrial wastewaters. In addition, they have the advantage of being prepared with less sodium hydroxide than the traditional preparations, decreasing the amount of wash water, besides reducing the amounts of peanut hulls disposed in the environment.

Interaction of violacein in models for cellular membranes: Regulation of the interaction by the lipid composition at the air-water interface

Karine Damaceno de Souza, Katia Regina Perez, Nelson Durán, Giselle Zenker Justo, Luciano Caseli
Publicado por Colloids and Interfaces B: Biointerfaces, 2017

Some biological properties of violacein are believed to be associated with their interactions with lipid surfaces, encouraging research on the identification of membrane sites capable of drug binding. In this study, we investigated the interaction of violacein with cell membrane models represented by Langmuir monolayers of selected lipids: one representing healthy cellular membranes: dipalmitoylphosphatidylcholine, DPPC, and the other one representing tumorigenic cellular membranes, dipalmitoylphosphatidylserine, DPPS. It is shown that even small amounts of the compound affect the surface pressure-area isotherms as well as the surface vibrational spectra of the lipid monolayers, which points to a significant interaction. Such effects depend on the electrical charge of the monolayer-forming molecules, with the drug activity being particularly distinctive for negatively charged lipids in relation to zwitterionic lipids. Morphological analysis also suggests that violacein at the air-water interface is homogenized when incorporated in both lipids. Although the interaction of violacein with the lipids affects viscoelastic and structural properties of the Langmuir monolayer, it is not present permeability through lipid bilayers, as investigated using liposomes. These results therefore may have important implications in understanding how violacein acts on specific sites of the cellular membrane, and evidence the fact that the lipid composition of the monolayer modulates the interaction with the lipophilic drug.

Influence of the metallic content on Pt-Ir/Nb2O5 catalysts for decalin selective ring opening

Viviana M. Benitez, Simone P. de Lima, Maria do Carmo Rangel, Doris Ruiz, Patricio Reyes, Carlos L. Pieck
Publicado por Catalysis Today, 2017

Ring opening of naphthenic rings on Pt-Ir catalysts supported on Nb2O5 was studied in this work. The catalysts were prepared by impregnation. In the case of the bimetallic catalyst, the total metallic load was kept constant while varying the individual quantity of impregnated Ir and Pt. The samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 sorption, NH3 TPD and model reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis). The decalin ring opening capacity of the catalysts was evaluated. Monometallic Ir and Pt catalysts as well as bimetallic catalysts were active towards cyclohexane dehydrogenation and cyclopentane hydrogenolysis. Regarding the bimetallic catalysts, an increase on the Pt content promoted the cyclohexane dehydrogenation while hindering the hydrogenolytic activity. In the selective ring opening of decalin, the bimetallic catalysts presented activities comparable to the monometallic catalysts. Nonetheless, Ir(0.3%)/Nb2O5 catalyst presented the highest selectivity towards ring opening products with the lowest selectivity towards dehydrogenated products.

Hydrogen purification over lanthanum-doped iron oxides by WGSR

Maria do Carmo Rangel, Peterson Santos Querino, Sarah Maria Santana Borges, Sergio Gustavo Marchetti, José Mansur Assaf, Doris Polett Ruiz Vásquez, Cristiane Barbieri Rodella, Tatiana de Freitas Silva, Alisson Henrique Marques da Silva, Adriana Paula Ramon
Publicado por Catalysis Today, 2017

Hydrogen technology has been greatly increased in last decades as a promising solution to protect the environment. When carbon-based feedstocks are used, such as natural gas, biomass and biogas, the water gas shift reaction (WGSR) plays an important step in the production of high pure hydrogen for several purposes. By this reaction, the residual carbon monoxide in the gaseous stream (coming from steam reforming of carbon-based feedstocks) can be converted to carbon dioxide and then removed from the stream, avoiding the poisoning of industrial metallic catalysts as well as of electrocatalysts in fuel cells. Aiming to obtain no toxic catalysts that can replace the commercial chromium-doped hematite catalysts, lanthanum-doped hematite was studied in this work. Iron oxide-based samples with different amounts of lanthanum (La/Fe (molar) = 0.02; 0.08 and 0.2) were obtained by sol-gel method and calcined at 600 °C. The catalysts were characterized by X-ray diffraction, specific surface area measurements, temperature programmed reduction, Raman spectroscopy, Mössbauer spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. It was found that lanthanum affected the textural and reducing properties of hematite, depending on the amount. Moreover, lanthanum oxide increased the activity of hematite by decreasing the size of hematite crystals and then increasing the number of exposed active sites. In addition, lanthanum favored hematite reduction to produce magnetite (active phase). The activity increased with the amount of lanthanum in solids, the lanthanum-richest sample being the most active catalyst.

Temperature probing and emission color tuning by morphology and size control of upconverting β-NaYb0.67Gd0.30F4:Tm0.015:Ho0.015 nanoparticles

Emille M. Rodrigues, Diogo A. Gálico, Italo O. Mazali and Fernando A. Sigoli
Publicado por Methods and Applications in Fluorescence, 2017

The chemical composition, shape and size of upconverting nanoparticles are known to have a great influence on their spectroscopic properties, such as the emission color and the emission intensity variation as a function of temperature. This work shows the color tuning and the thermal sensitivity of NaYb0.67Gd0.30F4:Tm0.015:Ho0.015 nanoparticles synthesized by two different approaches of the same synthetic method showing the influence of size and morphology, 250 nm hexagonal-plated and 30 nm spheroidal nanoparticles, on the visible upconversion color under NIR irradiation. According to the 1931-CIE diagram, the hexagonal-shaped nanoparticles show white light emission and the spheroidal ones generate red light emission under 980 nm excitation. Besides, the variation of the luminescence intensity ratio of Tm3+ emissions as a function of temperature was monitored in the 77–293 K temperature range, and the maximum relative sensitivity (Sm) of the samples reached 1.33% K−1 for the hexagonal-plated nanoparticles and 1.76% K−1 for the spheroidal nanoparticles. These maximum sensitivity values are higher compared to the ones found in the literature for temperature sensing using upconverting nanoparticles. These data suggest the versatility of these nanoparticles for applications on white light emission and nanothermometry.

Reversible Oxygen Vacancy Generation on Pure CeO2 Nanorods Evaluated by in Situ Raman Spectroscopy

Isaías de Castro Silva, Fernando Aparecido Sigoli and Italo Odone Mazali
Publicado por Journal of Physical Chemistry C, 2017

To observe oxygen vacancy influence over pure CeO2 Raman spectrum profile, nanorods were synthesized and submitted to an in situ strategy to generate or suppress reversibly the oxygen vacancies. No changes were observed in CeO2 nanorod Raman spectra. However, after the comminution of these nanorods, a reversible frequency downshift in CeO2 T2g Raman band was observed. The catalytic activities of CO oxidation were compared for both pristine and comminuted samples. The results indicate that the comminuted sample show higher catalytic activity than the pristine one. This enhancement on catalytic activity is attributed to the exposure of the CeO2 {110} crystals facets after the comminution process.

Star-shaped ZnO/Ag hybrid nanostructures for enhanced photocatalysis and antibacterial activity

George R. S. Andrade, Cristiane C. Nascimento, Zenon M. Lima, Erico Teixeira-Neto, Luiz P. Costa, Iara F. Gimenez
Publicado por Applied Surface Science, 2017

Zinc oxide (ZnO) particles with a star-shaped morphology have been synthesized by a novel and simple room-temperature method and decorated with silver nanoparticles (SNPs) for enhanced photocatalysis and bactericide applications. The presence of thiourea during the precipitation of ZnO in alkaline conditions allowed the control of morphological features (e.g. average size and shape) and the surface functionalization with thiocyanate ions (SCN). SNPs were deposited into the ZnO surface by a photoreduction method and their sizes could be easily controlled by changing the ZnO/AgNO3 ratio. The presence of SCN− on the semiconductor surface prevents uncontrollable growth of Ag nanoparticles into different morphologies and high degrees of polydispersity. XRD, SEM, TEM, FTIR, UV-vis-NIR and PL were employed for characterizing the structure, morphology and optical properties of the as-obtained pure and hybrid nanostructures. Finally, the hybrid ZnO/Ag particles have shown plasmon-enhanced performance for applications in photocatalysis and antibacterial activity compared to the pure ZnO counterpart. In this work, evaluation of the photodegradation of an aqueous methylene blue solution under UV-A irradiation and the antibacterial activity toward 4 bacterial strains, including Gram-positive bacteria Staphylococcus aureus (ATCC 43300, ATCC 25923 and ATCC 33591) and Gram-negative bacteria Pseudomonas aeruginosa (ATCC 27853).


Mayrla R. Lima, Haroldo C.B. Paula, Flávia O. M. S. Abreu, Rudson B. C. da Silva, Fernanda M. Sombra, Regina C. M. de Paula
Publicado por International Journal of Biological Macromolecules, 2017

Cashew gum (GC) is a polysaccharide whose structural modification has the potential to extend its applications on varied fields such as to the formation of self-organized nanoparticulated systems. In this work, a 23 factorial design was carried out, aiming at evaluation of the influence of the reactional parameters of an acetylation reaction on the final properties of cashew gum. The effects of temperature, reaction time and amount of acetylating agent on the reaction yield and degree of GC acetylation were investigated. Data obtained revealed that the aforementioned parameters influenced both yield and degree of acetylation. Statistical analysis showed that the different derivatives had their variables influenced mainly by temperature and interaction effect between the factors time and quantity of acetylating agent. Acetylated derivatives were obtained with yield higher than 90% and degrees of acetylation above 2.42. Data on the formation of self-organized systems, revealed particle sizes in the range 190–300 nm, where smaller particle sizes were obtained for derivatives with acetylation degrees lower than 1.5. Release profiles of Amphotericin-B incorporated in derivative nanoparticles, yielded 70% encapsulation efficiency and long release profiles, corroborating their potential application to delivery of hydrophobic active principles.

Selective cytotoxicity and luminescence imaging of cancer cells with a dipicolinato-based EuIII complex

J. H. S. K. Monteiro, D. Machado, L. M. de Hollanda, M. Lancellotti, F. A. Sigoli and A. de Bettencourt-Dias
Publicado por Chemical Communications, 10/2017

Four new species [Ln(dipicNH2)3]3− (Ln = LaIII, EuIII, GdIII, TbIII), with the ligand dipicNH22- (dipic = dipicolinato), were synthesized. Incubation of the EuIII complex with glioma NG97 and pancreatic cancer PANC1 cells showed that it penetrates the cell membrane and can be used to image the cells, while also being moderately cytotoxic.

Functionalization of Mesoporous Silicas as Strategy for Obtaining Nanocomposites with Controlled Graphitic Domains Quantity and Carbon Content

Mathias Strauss, João Paulo Vita Damasceno, Fernando Aparecido Sigoli and Italo Odone Mazali
Publicado por Journal of Nanoscience and Nanotechnology, 04/2017

We report in this work the use of a synthetic procedure to prepare silica-carbon composites with controlled carbon content and number of graphitic nanocarbon domains. This synthetic protocol was applied to prepare carbon nanostructures supported at two different amorphous silicas that have similar disordered pore system structure but different specific surface areas and pore volumes. The carbon nanostructures were obtained by the silica surface grafting with different amounts of 2,3-dihydroxynaphthalene (DN) using a dehydration reaction followed by pyrolysis at temperatures between 973 and 1173 K. We observed that the number of the graphitic nanodomains and the carbon loading at the pyrolysed samples could be tuned by the synthetic parameters during the functionalization and thermal treatment steps, as by the textural properties of the support.

Temperature-Driven Restructuring of Silver on AuAg Porous Nanotubes: Impact on CO Oxidation

Jean C. S. Costa, Renato V. Gonçalves, Érico Teixeira‐Neto and Liane M. Rossi
Publicado por Chemistry Select, 01/2017

Gold porous nanotubes (PNTs) prepared by the galvanic replacement reaction between HAuCl4 and a sacrificial metal nanowire have received attention as a platform for developing self‐sustained catalysts. However, due to an alloying process, the PNT contains a complex mixture of the two metals. Their thermal behavior, e. g., atom restructuring and morphological changes, under reaction conditions has been scarcely studied and difficult to predict. Here, we demonstrate that restructuring of silver atoms occurs after the thermal treatment of AuAg PNTs obtained through galvanic replacement reaction. Using various characterization techniques such as X‐ray diffraction, analytical electron microscopy, and X‐ray photoelectron spectroscopy, we were able to elucidate the structure and surface composition of this novel nanoarchitecture, which approaches an Ag nanoparticle‐decorated AuAg PNT like structure. The surface changes were studied through the catalytic oxidation of CO, a model reaction for surface science investigations.

Surface composition and structural changes on titanium oxide-supported AuPd nanoparticles during CO oxidation

A. A. Teixeira-Neto, R. V. Gonçalves, C. B. Rodella, L. M. Rossi and E. Teixeira-Neto
Publicado por Catalysis Science & Technology, 03/2017

To investigate the influence of morphological changes on the performance of bimetallic catalyst nanoparticles, two AuPd/TiO2 catalysts with the same starting composition were synthesized via thermal treatments in reducing (H2) or oxidizing (O2) atmospheres, resulting in different morphologies. The surface composition of the bimetallic particles evolved under a CO oxidation reaction environment, thereby changing the performance of both catalysts in repeated heat ramps. In the oxidized material, composed mainly of large AuPd particles and PdO particles, the CO oxidation reaction led to a broadening in the size distribution caused by the appearance of smaller particles, together with an increase in the surface Pd concentration. In the reduced material, the CO oxidation reaction led to particle aggregation, Pd oxidation, and surface Pd enrichment in Pd-rich particles. During the CO oxidation experiments, the oxidized material was activated (decrease of Tlight-off), while the reduced catalyst suffered a deactivation process (increase of Tlight-off). Our results showed that the catalysts converge to a common surface composition and performance, and this convergence seemed to be independent of the initial particle morphology.

One-pot organometallic synthesis of alumina-embedded Pd nanoparticles

Natália J. S. Costa, Lucas L. R. Vono, Robert Wojcieszak, Érico Teixeira-Neto, Karine Philippot and Liane M. Rossi
Publicado por Dalton Transactions, 09/2017

Herein we report a one pot organometallic strategy to access alumina-embedded Pd nanoparticles. Unexpectedly, the decomposition of the organometallic complex tris(dibenzylideneacetone)dipalladium(0), Pd2(dba)3, by dihydrogen in the presence of aluminum isopropoxide, Al(iPrO)3, and without extra stabilizers, was found to be an efficient method to generate a Pd colloidal solution. Careful characterization studies revealed that the so-obtained Pd nanoparticles were stabilized by an aluminum isopropoxide tetramer and 1,5-diphenyl-pentan-3-one, which was produced after reduction of the dba ligand from the organometallic precursor. Moreover, calcination of the obtained nanomaterial in air at 773 K for 2 h resulted in a nanocomposite material containing Pd nanoparticles embedded in Al2O3. This stabilization strategy opens new possibilities for the preparation of transition metal nanoparticles embedded in oxides.

Biosilica from diatomaceous earth as support to CdS-mediated photocatalysis in dry and aqueous phase

Cristiane C. Nascimento, George R. S. Andrade, Oseas S. Santos, Erico Teixeira Neto, Silvanio S. L. Costa and Iara F. Gimenez
Publicado por Materials & Design, 08/2017

This work reports the use of diatomite biosilica as support to deposition of homogeneously dispersed CdS nanoparticles by aqueous reaction. Time evolution of the process revealed that 30 min are sufficient to obtain well dispersed hexagonal CdS nanoparticles, without formation of external particles. Characterization by UV/visible reflectance spectroscopy allowed estimating nanocrystal size as ranging from 4 to 6 nm, while TEM and STEM images showed that those primary CdS nanocrystals formed aggregates with 14.2–71.8 nm depending on the reaction time. Photocatalysis in flow setup through glass column under solar light, under UVA irradiation and adsorption in dark conditions showed that the process under solar light was the most efficient. Photocatalytic tests in dry phase under solar light revealed that the presence of CdS favors dye degradation when compared to diatomite containing the adsorbed dye. Finally, photocatalysis of aqueous suspensions under solar light was also more efficient than adsorption or photolysis, following pseudo-first order kinetics with a half time of 46.2 min.

Direct comparison among the formation of terephthalate- and carbonate-intercalated Mg-Al-LDH: The influence of the high aluminum content

Inna M. Nangoi, Arnaldo C. Faro Jr., Wladmir F. Souza, Sandra S. X. Chiaro and Alexandre A. Leitão
Publicado por Applied Clay Science, 10/2017

First principles calculations based on Density Functional Theory (DFT) were used to investigate the standard thermodynamic potentials and also structural and electronic properties of terephthalate (TA) and carbonate intercalated Layered Double Hydroxides (LDH) with molar ratios, x = Al3 +/Al3 + +Mg2 +, equal to 0.25, 0.33 and 0.50. Herein we discuss how the interlayer species and formation of the LDH are influenced by the layer charge. Mg-Al-CO3 with high Al3 + content,x over 0.33, is hard to be obtained by synthetic methods in its pure phase, and LDH with high molar ratio is desirable for several applications such as intercalation reactions and obtainment of mixed oxides with better synergistic effects. This structure profile is easily to be acquired by the use of terephthalate as counterion than carbonate. The reason for this behaviour was found to be the competition among water molecules and anions for the interlayer sites. The dehydration process was simulated with excellent agreement with experimental data and showed important structural changes of TA in the interlayer space.

Charge carrier transport in defective reduced graphene oxide as quantum dots and nanoplatelets in multilayer films

Mawin J. M. Jimenez, Rafael F. Oliveira, Tiago P. Almeida, Rafael C. Hensel Ferreira, Carlos Cesar B. Bufon, Varlei Rodrigues, Marcelo A. Pereira-da-Silva, Ângelo L. Gobbi, Maria H. O. Piazzetta and Antonio Riul Jr
Publicado por Nanotechnology, 11/2017

Graphene is a breakthrough 2D material due to its unique mechanical, electrical, and thermal properties, with considerable responsiveness in real applications. However, the coverage of large areas with pristine graphene is a challenge and graphene derivatives have been alternatively exploited to produce hybrid and composite materials that allow for new developments, considering also the handling of large areas using distinct methodologies. For electronic applications there is significant interest in the investigation of the electrical properties of graphene derivatives and related composites to determine whether the characteristic 2D charge transport of pristine graphene is preserved. Here, we report a systematic study of the charge transport mechanisms of reduced graphene oxide chemically functionalized with sodium polystyrene sulfonate (PSS), named as GPSS. GPSS was produced either as quantum dots (QDs) or nanoplatelets (NPLs), being further nanostructured with poly(diallyldimethylammonium chloride) through the layer-by-layer (LbL) assembly to produce graphene nanocomposites with molecular level control. Current–voltage (I–V) measurements indicated a meticulous growth of the LbL nanostructures onto gold interdigitated electrodes (IDEs), with a space-charge-limited current dominated by a Mott-variable range hopping mechanism. A 2D intra-planar conduction within the GPSS nanostructure was observed, which resulted in effective charge carrier mobility (μ) of 4.7 cm2 V−1 s−1 for the QDs and 34.7 cm2 V−1 s−1 for the NPLs. The LbL assemblies together with the dimension of the materials (QDs or NPLs) were favorably used for the fine tuning and control of the charge carrier mobility inside the LbL nanostructures. Such 2D charge conduction mechanism and high μ values inside an interlocked multilayered assembly containing graphene-based nanocomposites are of great interest for organic devices and functionalization of interfaces.

Unsupported trimetallic Ni(Co)-Mo-W sulphide catalysts prepared from mixed oxides: Characterisation and catalytic tests for simultaneous tetralin HDA and dibenzothiophene HDS reactions

Yordy E. Licea, Ricardo Grau-Crespo, Luz A. Palacio and Arnaldo C. Faro Jr.
Publicado por Catalysis Today, 09/2017

Unsupported A-Mo-W (A = Ni or Co) sulphide catalysts were obtained from mixed oxides containing different W:Mo ratios. An in situ liquid-phase sulphidation of the mixed oxides in a batch reactor was followed by catalytic tests in a liquid-phase reaction (at 613 K and 70 bar), using a mixture of dibenzotiophene (DBT) and tetralin (THN) as the feed. After the catalytic tests, the bulk sulphide catalysts were characterised by nitrogen physical adsorption, XANES/EXAFS, SEM and HR-(S)TEM. The HR-TEM images showed randomly oriented, stacked-layer particles typical of Mo (W) sulphides and an elemental HR-STEM mapping evidenced Mo/W homogeneous distribution in the trimetallic sulphides. The EXAFS results for the trimetallic catalysts are consistent with the presence of nickel or cobalt sulphide domains, and Mo1-xWxS2 solid solutions. The intralayer Mo:W solid solutions were confirmed to be thermodynamically stable with respect to phase separation by DFT calculations, which were also used to aid in the interpretation of the EXAFS results. The effect of the W:Mo ratio on the catalytic properties of the Ni- and Co-containing series was found to be different. For the Ni series, increasing the W content caused an activity increase in THN hydrodearomatization (HDA) relative to DBT hydrodesulphurization (HDS), while it had little influence on the relative contribution of the direct desulphurisation (DDS) route with respect to the previous hydrogenation (HYD) route for DBT HDS. In contrast, for the Co series, the activities and selectivities were essentially insensitive to the W content. Both the Ni and Co series of unsupported sulphides were more selective for the HYD route in DBT HDS than a supported NiMo/Al2O3 catalyst.

Mixed NiMo, NiW and NiMoW sulfides obtained from layered double hydroxides as catalysts in simultaneous HDA and HDS reactions

Santiago Arias, Yordy E.Licea, Douglas Soares, Jean Guillaume Eon, Luz Amparo Palacio, Arnaldo C.Faro Jr.
Publicado por Catalysis Today, 11/2017

NiMoAl, NiWAl and NiMoWAl hydrotreating catalysts were prepared from NiAl-terephthalate layered double hydroxides (LDHs), by ion exchange of the therephthalate anion by heptamolybdate (Mo7O246−) and/or metatungstate (H2W12O406−). The Mo- and/or W-containing LDHs were sulfided, either by direct sulfidation (DS route) or after previous calcination (PC route).

Biomass-assisted Zeolite Syntheses as a Tool for Designing New Acid Catalysts

Benoît Louis, Elisa S. Gomes, Pit Losch, Gaëtan Lutzweiler, Tiago Coelho, Arnaldo Faro Jr., Joana F. Pinto, Cristiane S. Cardoso, Alessandra V. Silva and Marcelo M. Pereira
Publicado por ChemCatChem, 03/2017

The aim of this Concept article is to highlight different aspects of using biomass residues or extracted molecules in the synthesis of zeolites (mainly), aluminas and layered doubled hydroxides (LDHs). The strategies presented should serve as a basis for rationally preparing those aforementioned materials for catalytic purposes. Indeed, the presence of sugars, lignin, lignocellulosic biomass usually induces morphological/textural changes as well as (in some cases) modified chemical composition and surface properties.


Ivana Elena Camejo Aviles and Eduardo Galembeck
Publicado por Aprendizagem Significativa em Revista, 03/2017

Nesta pesquisa de natureza documental, questionamos em que medida a Teoria Cognitiva de Aprendizagem Multimídia (TCAM) de Mayer (2009) poderia incorporar os elementos da Teoria de Aprendizagem Significativa (TAS) na visão de Ausubel, Novak, Gowin e Moreira. Assim, desenvolvemos uma análise teórico-reflexiva dos elementos da TCAM que forneça evidências de seu nível de correspondência com a TAS. Os focos de interesse e categorias de análises desta análise crítica e reflexiva, foram definidos a priori pelos autores, tais como: conceptualização de aprendizagem, mecanismos para alcançar a aprendizagem e materiais didáticos para facilitar a aprendizagem. Embora a Teoria Cognitiva de Aprendizagem Multimídia e a Teoria de Aprendizagem Significativa representem dois robustos referenciais teóricos-pedagógicos com potencial para superar as limitações de ensino de ciências na atualidade, na opinião dos autores deste trabalho, a TCAM não incorpora elementos suficientes da TAS, gerando inconsistências teórico-pedagógicas e, portanto, posturas antagônicas entre as duas teorias.

A water-soluble Tb III complex as a temperature-sensitive luminescent probe

Jorge H. S. K. Monteiro, Fernando A. Sigoli and Ana de Bettencourt-Dias
Publicado por Canadian Journal of Chemistry, 11/2017

The water soluble [Tb(dipicCbz)3]3− (dipicCbz = 4-(9H-carbazol-9-yl-)pyridine-2,6-dicarboxylato) complex was isolated and evaluated as a temperature sensor in water. The 1:3 (TbIII:dipicCbz2−) stoichiometry in solution was confirmed by luminescence titration and high-resolution mass spectrometry. The quantum yield of sensitized emission is 3.8% ± 0.4% at 25.0 ± 0.1 °C, and the emission intensity depends on the temperature in the range of 5–70 °C with a relative thermal sensitivity of 3.4% °C−1 at 35 °C and temperature resolution < 0.01 °C in the range of 30–40 °C. The reversibility of this behavior was demonstrated for three heating–cooling cycles. Calculations of the energy gap between donor and acceptor show that the temperature dependence of the emission intensity is due to back-energy transfer from the Tb 5D4 excited state to the triplet and twisted intramolecular charge transfer (TICT) states of the dipicCbz. The assignment of one of the energy levels as a TICT state was confirmed by the temperature-dependent behavior of the phosphorescence band.

The Effect of Hydrothermal Treatment on the Morphologies and Optical Properties of Upconversion NaYF4: Ln3+ Crystals

Marcos A. Calil Júnior, Átila A. C. Melo, Emille M. Rodrigues, Fernando A. Sigoli and Marcelo O. Rodrigues
Publicado por Journal of the Brazilian Chemical Society, 09/2017

This work deals with the synthesis and characterization of upconversion NaYF4:Ln3+ crystals. Co-precipitation and hydrothermal methods were used to synthesize NaYF4:Ln3+ crystals. The experimental procedures were modified to obtain crystals in the cubic (α) phase, hexagonal (β) phase or a mixture between cubic and hexagonal (α/β) phases. Reaction temperature was maintained at 200 °C and the time of hydrothermal treatments were maintained at 24 and 48 h. The average diameter of the crystals ranged from 25 nm to 6.4 µm, depending on the chosen synthetic route. These materials can be applied in areas such as photodynamic therapy and bioimaging.

Multifunctional Nanocomposites of Natural Rubber Latex and Carbon Nanostructures

Carolina F. Matos, Fernando Galembeck and Aldo José G. Zarbin
Publicado por Revista Virtual de Química, 01/2017

Este trabalho descreve o preparo, caracterização e estudo das propriedades de materiais nanocompósitos multifuncionais obtidos entre a combinação do látex de borracha natural (NR) e quatro diferentes nanoestruturas de carbono: nanotubos de carbono, nanografite, óxido de grafeno e óxido de grafeno reduzido. O efeito da presença de cada nanoestrutura na morfologia e na melhora de propriedades da borracha natural foi estudado. A dispersão e a boa aderência de todas as nanoestruturas na matriz polimérica foram confirmadas por imagens de microscopia eletrônica de varredura. Os materiais obtidos apresentam multifuncionalidade, com novas propriedades elétricas, mecânicas e químicas, moduladas de acordo com a natureza da espécie de nanocarbono utilizada, fazendo com que esses materiais apresentem um grande potencial para aplicações em um elevado número de sistemas.

Nanoparticulated Nitric Oxide Donors and their Biomedical Applications

Amedea B. Seabra and Nelson Duran
Publicado por Mini-Reviews in Medicinal Chemistry, 04/2017


M. de Sousa, C.H.Z. Martins, L.S. Franqui, L.C. Fonseca, F.S. Delite, D.S.T. Martinez and O.L. Alves
Publicado por Jounal of Materials Chemistry B, 04/2018

In this work, graphene oxide (GO) was covalently functionalized with D-mannose (man-GO) using mannosylated ethylenediamine. XPS (C1s and N1s) confirmed the functionalization of GO through the binding energies at 288.2 eV and 399.8 eV, respectively, which are attributed to the amide bond. ATR-FTIR spectroscopy showed an increase in the amine bond intensity, at 1625 cm−1 (stretching CO), after the functionalization step. Furthermore, the man-GO toxicity to human red blood cells (hemolysis) and its nanobiointeractions with human plasma proteins (hard corona formation) were evaluated. The mannosylation of GO drastically reduced its toxicity to red blood cells. SDS-PAGE analysis showed that the mannosylation process of GO also drastically reduced the amount of the proteins in the hard corona. Additionally, proteomics analysis by LC–MS/MS revealed 109 proteins in the composition of the man-GO hard corona. Finally, this work contributes to future biomedical applications of graphene-based materials functionalized with active biomolecules.



M. Sousa, L.A.V. Luna, L.C. Fonseca, S. Giorgio and O.L. Alves
Publicado por ACS Applied Nano Materials, 01/2018

In this work, we developed and screened the potential antitumor activity of a nanocarrier based on graphene oxide (GO) and folic acid (FA) for the delivery of chemotherapy drugs. GO was synthesized by the graphite exfoliation process. FA was linked to PEG (4,7,10-trioxa-1,13-tridecanediamine) to form FA–PEG, followed by coupling to the GO surface. Camptothecin (CPT) was further adsorbed on GO for use as a drug model in the delivery study. The synthesis of the intermediate FA–PEG molecule and coupling to GO for the formation of the GO–FA nanocarrier were confirmed by basic and state-of-the-art characterization techniques, including infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), electrospray ionization (ESI) mass spectrometry, transmission electron microscopy (TEM), and magic-angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. FTIR spectroscopy showed a significant reduction in the signal intensity of the carboxylic groups after the functionalization of GO with FA–PEG. TGA of GO–FA revealed that approximately 20% of the functional groups were from FA–PEG. GO–FA indicated a high CPT loading capacity (37.8%). In vitro studies confirmed prolonged drug release over 200 h. Acidic pH (5.0) slowed the release of CPT from the nanocarrier compared to that at physiological pH (7.4). The toxicity screening of GO–FA and GO–FA + CPT was investigated for two widely studied preclinical cell models: J774, a tumor cell with macrophage phenotype and high proliferation rate; and HepG2, a tumor cell obtained from human hepatocellular carcinoma with folate transporters. The toxicity of the GO–FA nanocarrier without drug loading was dependent on the cell type and presented no toxicity to J774 but high toxicity to HepG2. The presence of FA in the nanocarrier loaded with CPT was crucial to achieve apoptosis in both tumor cell lines. In addition, confocal microscopy revealed both the adhesion and internalization of the FITC-labeled GO–FA by the tumor cell lines.

DOI: 10.1021/acsanm.7b00324


A.P.M. Monteiro, R.D. Holtz, L.C. Fonseca, C.H.Z. Martins, M. Sousa, L.A.V. Luna, D.S. Maia and O.L. Alves
Publicado por Chemical Record (Chemical Society of Japan), 01/2018

Silver vanadates have been widely investigated because of their many interesting properties and their potential use in several applications. In addition to this, a large number of groups have investigated silver vanadates in the form of nanostructures. Here, we address first the synthesis and properties of nanosilver vanadate. Different techniques, such as precipitation, thermal decomposition, hydrothermal treatment, and sol-gel, are among the methods that have been employed for the controlled synthesis of silver vanadate. The use of nanosilver vanadate for the development of novel electronic devices, catalysts, and antibacterial agents for industry and biomedical applications will then be discussed. In this sense, the present review highlights the major advances regarding the synthesis, properties and applications of nanostructured silver vanadates.DOI:10.1002/tcr.201700086


L.C. Fonseca, M.M. de Araújo, A.C.M. de Moraes, D.S. da Silva, A.G. Ferreira, L.S. Franqui, D.S.T. Martinez and O.L. Alves
Publicado por Journal of Applied Surface Science, 04/2018

The current work refers to the development of a novel nanocomposite based on graphene oxide (GO) and mesoporous amino silica nanoparticles (H2N-MSNs) and its biological interaction with red blood cells (RBCs) and human blood plasma toward the investigation of nanobiointeractions. Silica nanoparticles and several graphene oxide-based materials are, separately, known for their high hemolytic potential and strong interaction with human plasma proteins. In this context, the GO-MSN interaction and its influence in minimizing the reported effects were investigated. The materials were synthesized by covalently attaching H2N-MSNs onto the surface of GO through an amidation reaction. GO-MSN nanocomposites were obtained by varying the mass of H2N-MSNs and were characterized by FTIR, NMR, XRD, TGA, zeta potential and TEM. The characterization results confirm that nanocomposites were obtained, suggest covalent bond attachment mostly by amine-epoxy reactions and evidence an unexpected reduction reaction of GO by H2N-MSNs, whose mechanism is proposed. Biological assays showed a decrease of hemolysis (RBC lysis) and a minimization of the interaction with human plasma proteins (protein corona formation). These are important findings toward achieving in vivo biocompatibility and understanding the nanobiointeractions. Finally, this work opens possibilities for new nanomedicine applications of GO-MSN nanocomposites, such as drug delivery system.


J.V. Silveira, L.L. Vieira, A.L. Aguiar, P.T.C. Freire, J. Mendes Filho, O.L. Alves and A.G. Souza Filho
Publicado por Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 03/2018

MoO3 nanoribbons were studied under different pressure conditions ranging from 0 to 21GPa at room temperature. The effect of the applied pressure on the spectroscopic and morphologic properties of the MoO3 nanoribbons was investigated by means of Raman spectroscopy and scanning electron microscopy techniques. The pressure dependent Raman spectra of the MoO3 nanoribbons indicate that a structural phase transition occurs at 5 GPa from the orthorhombic α-MoO3 phase (Pbnm) to the monoclinic MoO3-II phase (P21/m), which remains stable up to 21 GPa. Such phase transformation occurs at considerably lower pressure than the critical pressure for α-MoO3 microcrystals (12 GPa). We suggested that the applanate morphology combined with the presence of crystalline defects in the sample play an important role in the phase transition of the MoO3 nanoribbons. Frequencies and linewidths of the Raman bands as a function of pressure also suggest a pressure-induced morphological change and the decreasing of the nanocrystal size. The observed spectroscopic changes are supported by electron microscopy images, which clearly show a pressure-induced morphologic change in MoO3 nanoribbons.


N. Bibi, R. B. Guerra, L. E. S. C. Huaman & A. L. B. Formiga
Publicado por Acta Crystallographica Section E, 05/2018

The crystal structure of the title compound, [Ru(C7H6N4)3](PF6)2.3H2O, a novel Ru II complex with the bidentate ligand 2-(1H-imidazol-2-yl)pyrimidine, comprises a complex cation in the meridional form exclusively, with a distorted octahedral geometry about the ruthenium(II) cation. The Ru—N bonds involving imidazole N atoms are comparatively shorter than the Ru—N bonds from pyrimidine because of the stronger basicity of the imidazole moiety. The three-dimensional hydrogen-bonded network involves all species in the lattice with water molecules interacting with both counter-ions and NH hydrogen atoms from the complex. The supramolecular structure of the crystal also shows that two units of the complex bind strongly through a mutual N—H...N bond. The electronic absorption spectrum of the complex displays an asymmetric band at 421 nm, which might point to the presence of two metal-to-ligand charge-transfer (MLCT) bands. Electrochemical measurements show a quasi-reversible peak referring to the RuIII/RuII reduction at 0.87 V versus Ag/AgCl.


Maitê Munhoz Scherer, Catina Prochnow, Andressa Borin Venturini, Gabriel Kalil Rocha Pereira, Thiago Augusto de Lima Burgo, Marília Pivetta Rippe & Luiz Felipe Valandro
Publicado por Dental Materials, 05/2018

To evaluate the effect of different glass-ceramic surface treatments and aging on the fatigue failure load of a lithium disilicate glass-ceramic adhesively cemented to a dentin analogue material.
One hundred and twenty (120) disc-shaped lithium disilicate specimens (Ø = 10 mm, thickness = 1.5 mm) were produced and randomly allocated (n = 20) into 6 groups, considering 2 study factors: “surface treatment” in 3 levels (SIL—silane application only; HF5+SIL—5% hydrofluoric acid etching and silane application; ME&P—etching with an one-step ceramic primer), and “storage” in 2 levels (baseline—storage for 7 days; aging—storage for 90 days + 12,000 thermal cycles). Ceramic discs were adhesively cemented to discs of a dentin analogue material (Ø = 10 mm, thickness = 2.0 mm) following the manufacturers’ instructions. The fatigue failure load was determined by the staircase approach (250,000 cycles; 20 Hz; initial load = 1050 N [∼70% of mean load-to-failure]; step size = 52.5 N [5% of initial load]). Micro-morphologic, fractographic, and atomic force microscope analysis were also performed. Fatigue failure load data were evaluated by one-way ANOVA, Bonferroni and t-tests for independent samples.
HF5+SIL presented higher fatigue failure load in both conditions (baseline and aging); ME&P presented intermediary mean values, while the SIL group presented the worst performance. All groups had a statistically significant decrease in the fatigue performance after aging.
Hydrofluoric acid followed by silane application showed the best fatigue performance for an adhesively-cemented lithium disilicate ceramic. Aging negatively influenced the fatigue performance for all tested groups.

Graphene Oxide as Scaffolds for Stem Cells: An Overview.

Marcela Durán, Angela Cristina Malheiros Luzo, Joel Gonçalves de Souza, Wagner José Fávaro, Patrick Garcia, Nelson Durán
Publicado por Current Molecular Medicine, 12/2018

Graphene and graphene oxide topography have an effect on the fate of stem cells such as adhesion, differentiation, and proliferation. This overview clearly shows that a new design and manipulation of associated graphene oxide stem cell culture platforms are of paramount importance as a focus in stem cell to tissue engineering applications. This overview also proposes that a film of graphene oxide is an efficient platform to modulate structure and function of multipotent mesenchymal stem/stromal cells (MSCs) and in special human adipose tissue derived mesenchymal stromal/stem cells (AT-MSCs). The implication of graphene oxide on osteogenesis, neurogenesis, oligodendrogenesis, adipogenic and epithelial differentiation is also discussed. Graphene oxide toxicity on stem cells and the importance of GO application on ATMSCs differentiation and proliferation are final topics that are being discussed.

Cellulose nanocrystals as carriers in medicine and their toxicities: A review.

Amedea B.Seabra, Juliana S.Bernardes, Wagner J.Fávaro, Amauri J.Paula, NelsonDurán
Publicado por Carbohydrate Polymers, 02/2018

Cellulose nanocrystals (CNCs) are crystalline nanoparticles that present myriad applications. CNCs are produced from a variety of renewable sources, and they can be chemically modified. Although there are promising perspectives for introducing CNCs into pharmaceutical formulations, prior to achieving commercial products the influence of many parameters such as extraction and toxicity of the resulting products must be revealed. Since there is great physicochemical flexibility in the steps of obtaining and conjugating CNCs, there are uncountable and complex outcomes from the interactions of those parameters. We present a discussion that helps to unveil the whole panorama on the use of CNCs as drug delivery systems. The methods of producing CNCs are correlated to the resulting nanotoxicity from the cellular to organism level. This review points to relevant concerns that must be overcome to attain safe use of these nanostructures. We also discuss the patents and commercially available products based on CNCs.


Nelson Durán & Wagner José Fávaro
Publicado por Journal of the Brazilian Chemical Society, 05/2018

The primary treatment for high-grade non-muscle invasive bladder cancer (NMIBC) is based on surgery by transurethral resection of bladder tumor (TURBT), followed by intravesical immunotherapy with Bacillus Calmette-Guerin (BCG) to prevent recurrence and to reduce the tumor progression. However, BCG therapy shows several undesirable effects. The current treatment on NMIBC is doxorubicin (DOX), but with high toxicity. Our nanotechnology strategy was done through scaffolds for the NMIBC treatment: graphene oxide (GO) and a nanostructured lipid carrier (NLC). A GO hybrid for administration of DOX and small interfering RNA (siRNA) was developed. This hybrids administered in vivo against NMIBC in rats gave absence of lesions. NLC was prepared by using a mixture of two lipids stabilized by a surfactant and DOX by high homogenization pressure technique. In this case showed a 20% of the animals exhibited benign lesions (papillary hyperplasia), however, in the presence of siRNA reached 40% of rats with benignant lesions. These two scaffolds are potential new drugs for DOX for bladder cancer treatment without any cardiotoxicity problems.


Nelson Durán & Wagner José Fávaro
Publicado por Química Nova, 05/2018

The ecological processes in which metabolites with industrial or medical applications are produced are of great importance. Magnesium plays many important roles in environmental and medical applications. Phosphorus is obtained by mining. It is estimated to have a very limited half-life and expected to be depleted as a resource in 100 years. Its recovery by mining and subsequent marketing as phosphate has important environmental implications. These processes are part of an important recovery technology. Bacteria have contributed to the formation of minerals since the advent of life on Earth. Bacterial and/or fungal biomineralizations play a critical role in biogeochemical cycles. These processes have important technological and environmental applications. In many past publications dealing with bacterial and fungal recovery of phosphates as insoluble products, magnesium played an important role. This is a review of recent progress in the microbial recovery of biogenic magnesium phosphate compounds, their importance, and their roles in treatment of several human diseases.

Advances and Perspectives in Urinary Bladder Cancer Nanotherapy.

Rogério Cardoso da Silva, Joel Gonçalves de Souza, Amedea Barozzi Seabra, Nelson Durán, Wagner José Fávaro
Publicado por European Medical Journal Urology, 05/2018

Bladder cancer treatment remains a challenge in the pharmaceutical field due to the recurrence and progression of the disease, as well as the pronounced side effects associated with the available therapeutic modalities. Although important strategies have been investigated in different clinical trial phases, efficient and well-tolerated treatment approaches need to be developed to improve therapeutic efficacy and the quality of life for bladder cancer patients. This review discusses conventional protocols used in the clinical setting, detailing the use of Bacillus Calmette–Guérin, new immunomodulators, and drug delivery systems. New therapeutic approaches have been investigated with the aim of better therapeutic efficacy with low rates of recurrence and progression of non-muscle invasive bladder cancer and muscle invasive bladder cancer. Therefore, this review highlights the progression of therapy with the use of conventional treatments and the recent progress achieved from the use of innovative strategies, such as nanoparticles for sustained, controlled drug delivery and increased drug uptake by tumour cells.

Effects of intravesical therapy with platelet-rich plasma (PRP) and Bacillus Calmette-Guérin (BCG) in non-muscle invasive bladder cancer

Lara Paro Dias, Ângela C. Malheiros Luzo, Bruno B. Volpe, Marcela Durán, Sofia E. M. Galdames, Luiz A. B. Ferreira, Nelson Durán, Wagner J. Fávaro
Publicado por Tissue and Cell, 06/2018

This study describes the effects of a promising therapeutic alternative for non-muscle invasive bladder cancer (NMIBC) based on Bacillus Calmette-Guerin (BCG) intravesical immunotherapy combined with Platelet-rich plasma (PRP) in an animal model. Furthermore, this study describes the possible mechanisms of this therapeutic combination involving Toll-like Receptors (TLRs) 2 and 4 signaling pathways. NMIBC was induced by treating female Fischer 344 rats with N-methyl-N-nitrosourea (MNU). After treatment with MNU, the animals were distributed into four experimental groups: Control (without MNU) group, MNU (cancer) group, MNU + PRP group, MNU + BCG group and MNU + PRP + BCG group. Our results demonstrated that PRP treatment alone or associated with BCG triggered significant cytotoxicity in bladder carcinoma cells (HTB-9). Animals treated with PRP associated to BCG clearly showed better histopathological recovery from the cancer state and decrease of urothelial neoplastic lesions progression in 70% of animals when compared to groups that received the same therapies administered singly. In addition, this therapeutic association led to distinct activation of immune system TLRs 2 and 4-mediated, resulting in increased MyD88, TRIF, IRF3, IFN-γ immunoreactivities. Taken together, the data obtained suggest that interferon signaling pathway activation by PRP treatment in combination with BCG immunotherapy may provide novel therapeutic approaches for non-muscle invasive bladder cancer.

Biogenic silver nanoparticles inducing Leishmania amazonensis promastigote and amastigote death in vitro.

Fanti, J.R., Tomiotto-Pellissier, F., Miranda-Sapla, M.M., Cataneo, A.H.D., Andrade, C.G.T.J., Panis, C., Rodrigues, J.H.S., Wowk, P.F., Kuczera, D., Costa, I.N., Nakamura, C.V., Nakazato, G., Durán, N., Pavanelli, W.R., Conchon-Costa, I
Publicado por Acta Tropica, 02/2018

American Cutaneous Leishmaniasis (ACL) is a zoonosis caused by Leishmania protozoa. The ACL chemotherapy available is unsatisfactory motivating researches to seek alternative treatments. In this study, we investigated the action of biogenic silver nanoparticle (AgNp-bio) obtained from Fusarium oxysporium, against Leishmania amazonensis promastigote and amastigote forms. The AgNp-bio promastigote treatment results in promastigote death leading to apoptosis-like events due an increased production of reactive oxygen species (ROS), loss of mitochondrial integrity, phosphatidylserine exposure and damage on promastigotes membrane. In L. amazonensis infected macrophages, AgNp-bio treatment was still able to reduce the percentage of infected macrophages and the amount of amastigotes per macrophage, consequently, the amount of promastigotes recovered. This leishmanicidal effect was also accompanied by a decrease in the levels of ROS and nitric oxide. By observing the ultrastructural integrity of the intracellular amastigotes, we found that the AgNp-bio treatment made a significant damage, suggesting that the compound has a direct effect on intracellular amastigotes. These results demonstrated that AgNp-bio had a direct effect against L. amazonensis forms and acted on immunomodulatory ability of infected macrophages, reducing the infection without inducing the synthesis of inflammatory mediators, which continuous stimulation can generate and aggravate leishmaniotic lesions. Overall, our findings suggest that the use of AgNp-bio stands out as a new therapeutic option to be considered for further in vivo investigations representing a possible treatment for ACL.

Nitric oxide donors for prostate and bladder cancers: Current state and challenges.

Seabra, A.B., Durán, N.
Publicado por Eurpean Journal of Pharmacology, 05/2018

Nitric oxide (NO) is an endogenous molecule that plays pivotal physiological and pathophysiological roles, particularly in cancer biology. Generally, low concentrations of NO (pico- to nanomolar range) lead to tumor promotion. In contrast, high NO concentrations (micromolar range) have pro-apoptotic functions, leading to tumor suppression, and in this case, NO is involved in immune surveillance. Under oxidative stress, inducible NO synthase (iNOS) produces high NO concentrations for antineoplastic activities. Prostate and bladder cancers are the most commonly detected cancers in men, and are related to cancer death in males. This review summarizes the state of the art of NO/NO donors in combating prostate and bladder cancers, highlighting the importance of NO donors in cancer treatment, and the limitations and challenges to be overcome. In addition, the combination of NO donors with classical therapies (radio- or chemotherapy) in the treatment of prostate and bladder cancers is also presented and discussed. The combination of NO donors with conventional anticancer drugs is reported to inhibit tumor growth, since NO is able to sensitize tumor cells, enhancing the efficacy of the traditional drugs. Although important progress has been made, more studies are still necessary to definitely translate the administration of NO donors to clinical sets. The purpose of this review is to inspire new avenues in this topic.

Synthesis of extracellular stable gold nanoparticles by Cupriavidus metallidurans CH34 cells.

Montero, F., Durán, N., Seeger, M.
Publicado por IET Nanobiotechnology, 01/2018

In this study, spontaneous synthesis of a gold (Au) colloid using cells of Cupriavidus metallidurans CH34 is reported, and compared with results obtained using cells of the model bacterium Escherichia coli MG1655. To investigate the synthesis mechanism, bacterial biomass and secretomes from both strains were incubated with Au(III) ions. Only CH34 cells were capable of producing extracellular dispersions of Au nanoparticles (NPs). Transmission electron microscopy images showed that AuNPs morphology was dominated by triangular and decahedral nanostructures. Energy dispersive X-ray spectroscopy and Fourier transform infrared spectra showed the presence of sulphur and vibrations associated to proteins. Average AuNPs diameter was obtained by dynamic light-scattering measurements (DLS), NP tracking analysis measurements and analysis of electron microscopy images. Moreover, DLS measurements showed that the biogenic colloid was stable after exposure to ultrasound, high ionic strength and extreme pH conditions. The biogenic AuNPs produced by strain CH34 did not show antibacterial activity, in contrast to biogenic silver NPs. Comparative bioinformatic analysis of genomes from strain CH34 and strain MG1655 showed potential CH34 proteins that may be electron donors during reduction of Au(III) ions. On the basis of these results, a mechanism for the extracellular Au reduction by strain CH34 is proposed.

Applications of hesperidin as an anticancer pro-drug: Phytotherapy or an alternative chemotherapy.

Stanisic, D., Costa, A.F.,Cruz, G., Durán, N., Tasic, L.
Publicado por Studies in Natural Products Chemistry, Elsevier B.V., Pre-publ. 05/2018. Release: 08/2018

Hesperidin is an abundant flavanone and a cheap by-product of the citrus industry. It is especially present in oranges and lemons, and it can make up to 14% of the weight of an immature orange fruit. It has many interesting properties in terms of its biological activity, which include its anticancer prodrug effects against different cancer cell lines. This review discusses flavonoids, with a particular emphasis on hesperidin; it considers their phytochemical data, the known and/or hypothesized mechanisms of action based on structural data, and their chemoprotective roles in carcinogenesis. There are many different kinds of cancer in which it is known that bioflavonoids and hesperidin can act effectively, such as colon cancer (adenoma and adenocarcinoma), breast cancer, melanoma, prostate cancer, hepatocellular carcinoma, and many others, as well as in metastasis reduction. It is also known that in lung, liver, breast, stomach, and colon cancer, they probably act through the promotion of apoptosis in cancer cells via multiple mechanisms. Also, antiinflammatory properties have been described that may cause a reduction in proinflammatory mediators and enzymes that participate in the carcinogenesis process. Similarly, hesperidin and other bioflavonoids may improve antioxidant defense mechanisms by increasing the levels of enzymatic and nonenzymatic antioxidants. Finally, special attention has been paid to drug delivery systems that are described in the patents published on their use as drugs in chemotherapy.

Hybrid nanomembrane-based capacitors for the determination of the dielectric constant of semiconducting molecular ensembles

Paula A. Petrini, Ricardo M. L. Silva, Rafael F. de Oliveira, Leandro Merces, Carlos C Bof Bufon
Publicado por Nanotechnology, 05/2018

Avanços consideráveis no campo da eletrônica molecular foram alcançados nos últimos anos. Entretanto, um desafio ainda persistente é a exploração das propriedades eletrônicas de moléculas totalmente integradas a dispositivos. Tipicamente, essas propriedades moleculares são investigadas com a utilização de técnicas sofisticadas, incompatíveis com uma tecnologia prática de dispositivos, como por exemplo a microscopia de varredura por tunelamento (STM). A incorporação de materiais moleculares em dispositivos não é uma tarefa trivial, pois as dimensões típicas de contatos elétricos são muito maiores que as dos filmes moleculares. Para resolver este problema, reportamos aqui capacitores híbridos que utilizam nanomembranas mecanicamente compatíveis para encapsular conjuntos moleculares ultra-finos, de forma a possibilitar a investigação de propriedades dielétricas moleculares. Como material de análise, a ftalocianina de cobre (II) (CuPc) foi escolhida, já que ainda faltam informações sobre sua constante dielétrica (kCuPc) em escala molecular. Neste trabalho, capacitores híbridos ultracompactos contendo nanomembranas metálicas, camadas isolantes de Al2O3 e conjuntos moleculares de CuPc foram fabricados e avaliados. O Al2O3 desempenha o papel de isolante elétrico no sistema, evitando curto-circuitos através das placas do capacitor, uma vez que o filme molecular é consideravelmente fino (<30 nm). A partir das medidas elétricas de dispositivos com diferentes espessuras de camadas moleculares, a constante dielétrica da CuPc foi determinada de forma confiável (kCuPc = 4,5 ± 0,5). Os resultados sugerem uma leve contribuição da orientação molecular nas propriedades dielétricas da CuPc. O capacitor baseado em nanomembranas relatado é uma estratégia viável para a caracterização dielétrica de conjuntos moleculares ultrafinos integrados a uma tecnologia de dispositivo prática e real.

Single-Electron Charging Effects in Hybrid Organic/Inorganic Nanomembrane-Based Junctions

Rafael Furlan de Oliveira, Leandro Merces, Felipe Marques, Érico Teixeira-Neto, Davi Henrique Starnini de Camargo, Carlos César Bof Bufon
Publicado por The Journal of Physical Chemistry C, 02/2018

A transferência controlada de um elétron individual em dispositivos é uma das rotas viáveis para novos tipos de tecnologia. Entretanto, aplicações inovadoras demandam estratégias diferenciadas para fabricar e avaliar tais dispositivos, chamados de SEDs (do inglês, single eléctron devices). Neste trabalho, um SED híbrido – que combina um conjunto molecular semicondutor a nanopartículas metálicas oriundas da migração de átomos induzida pelo campo elétrico – é demonstrado. Tal dispositivo foi fabricado usando uma plataforma integrada, baseada em nanomembranas enroladas que conectam os conjuntos moleculares e formam junções túnel na nano escala. A combinação de altos campos elétricos (1-4 MV/cm), pontos de contato nos eletrodos, baixas temperaturas (10 K) e camadas moleculares ultrafinas (< 10 nm) leva à migração de nanopartículas de ouro provenientes dos eletrodos para dentro do conjunto molecular no canal da junção. Este fenômeno pode ser tanto observado em junções recém preparadas como também em junções com migração induzida intencionalmente pela aplicação de campo (> 1 MV/cm). As nanopartículas propelidas se tornam armadilhadas no interior do material molecular e agem como ilhas de Coulomb em uma junção de tunelamento duplo. Como resultado, efeitos de carga individual podem ser observados – isto é, bloqueio de Coulomb e degraus de condutância. A referida migração metálica induzida pelo campo abre novas possibilidades para a criação de SEDs inovadores e mais complexos, utilizando diferentes materiais. De outra perspectiva, a difusão metálica reportada neste trabalho é também importante uma vez que tal fenômeno pode, eventualmente, mascarar respostas elétricas que deveriam depender apenas de moléculas.

Low-cost and mass-production microfluidic electrochemical double-layer capacitors for fast, sensitive, and selective cancer diagnosis.

Ricardo A. G. de Oliveira, Caroline Y. N. Nicoliche, Anielli M. Pasqualeti, Flavio M. Shimizu, Iris R. Ribeiro, Matias E. Melendez, André L. Carvalho, Angelo L. Gobbi, Ronaldo C. Faria, E Renato S. Lima.
Publicado por ACS Analytical Chemistry, 06/2018

This technical note describes a new microfluidic sensor that combines low-cost (US$0.97) with large-scale manufacturing and user-friendly, fast, sensitive, and accurate quantification of cancer biomarker. The electrodes consisted of cost-effective bare stainless-steel capillaries, whose mass-production is already well-established. These capillaries were used as received, without any surface modification. Microfluidic chips containing electrical double-layer capillary capacitors (μEDLC) were obtained by a cleanroom- free prototyping that allows the fabrication of dozens to hundreds of chips in 1 h. This sensor provided the successful quantification of CA 15-3, a biomarker protein for breast cancer, in serum samples from cancer patients. Antibody-anchored magnetic beads were utilized for immunocapture of the marker and, then water was added to dilute the protein. Next, the CA 15-3 detection (< 2 min) was conducted in a label-free mode without using redox probes, secondary Ab, or signal amplification strategies. In addition, the capacitance tests presented low sample volume (5 μL) and high sensitivity utilizing bare capillaries in a new design for double-layer capacitors. The achieved limit-of-detection (92.0 μU mL–1) is lower than the most approaches reported in the literature for CA15-3, which are usually based on nanostructured electrodes.

Multifunctional hybrid aerogels: hyperbranched polymer-trapped mesoporous silica nanoparticles for sustained and prolonged drug release

Heveline D. M. Follmann, Osvaldo N. Oliveira, Jr, Danielle Lazarin-Bidóia, Celso V. Nakamura, Xiaoxi Huang,TewodrosAsefa, Rafael Silva
Publicado por Nanoscale, 01/2018

In this study, we show the synthesis of novel hybrid organic–inorganic aerogel materials with one-dimensionally aligned pores and demonstrate their use as sustained and prolonged release systems for a hydrophobic drug. The materials are synthesized by trapping mesoporous silica nanoparticles within a hyperbranched polymer network made from poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The synthetic method involves dispersing mesoporous silica nanoparticles in a polymer solution, then freeze-drying the solution, and finally subjecting the resulting materials to high temperature to activate a solid-state condensation reaction between PVA and PAA. Before trapping the mesoporous silica nanoparticles within the hyperbranched polymeric network, their pores are decorated with hydrophobic groups so that they can serve as good host materials for hydrophobic drugs. The potential application of the hybrid aerogels as drug carriers is demonstrated using the hydrophobic, anti-inflammatory agent dexamethasone (DEX) as a model drug. Due to their hydrophobic pores, the hybrid aerogels show excellent drug loading capacity for DEX, with an encapsulation efficiency higher than 75%. Furthermore, the release pattern of the payloads of DEX encapsulated in the aerogels is highly tailorable (i.e., it can be made faster or slower, as needed) simply by varying the PVA-to-PAA weight ratio in the precursors, and thus the 3-dimensional (3-D) structures of the cross-linked polymers in them. The materials also show sustained drug release, for over 50 days or more. In addition, the aerogels are biocompatible, as demonstrated with Vero cells, and greatly promote the cell proliferation of L929 fibroblasts. Also, the nanoparticles functionalized with quaternary groups and dispersed within the aerogels display bactericidal activity against E. coli, S. aureus, B. subtilis, and P. aeruginosa. These new hybrid aerogels can, thus, be highly appealing biomaterials for sustained and prolonged drug release, such as wound dressing systems.

The Inclusion of Chitosan in Poly-ε-caprolactone Nanoparticles: Impact on the Delivery System Characteristics and on the Adsorbed Ovalbumin Secondary Structure

Jesus, S.; Fragal E. H.; Rubira, A.F.; Muniz E.C.; Valente A.J.M.; Borges, O.
Publicado por AAPS PharmSciTech, 01/2018

This report extensively explores the benefits of including chitosan into poly-ε-caprolactone (PCL) nanoparticles (NPs) to obtain an improved protein/antigen delivery system. Blend NPs (PCL/chitosan NPs) showed improved protein adsorption efficacy (84%) in low shear stress and aqueous environment, suggesting that a synergistic effect between PCL hydrophobic nature and the positive charges of chitosan present at the particle surface was responsible for protein interaction. Additionally, thermal analysis suggested the blend NPs were more stable than the isolated polymers and cytotoxicity assays in a primary cell culture revealed chitosan inclusion in PCL NPs reduced the toxicity of the delivery system. A quantitative 6-month stability study showed that the inclusion of chitosan in PCL NPs did not induce a change in adsorbed ovalbumin (OVA) secondary structure characterized by the increase in the unordered conformation (random coil), as it was observed for OVA adsorbed to chitosan NPs. Additionally, the slight conformational changes occurred, are not expected to compromise ovalbumin secondary structure and activity, during a 6-month storage even at high temperatures (45°C). In simulated biological fluids, PCL/chitosan NPs showed an advantageous release profile for oral delivery. Overall, the combination of PCL and chitosan characteristics provide PCL/chitosan NPs valuable features particularly important to the development of vaccines for developing countries, where it is difficult to ensure cold chain transportation and non-parenteral formulations would be preferred.

Mechanically improved polyvinyl alcohol-composite films using modified cellulose nanowhiskers as nano-reinforcement

Cristiane Spagnol, Elizângela. H. Fragal, Maria A.Witt, Heveline D.M. Follmann, Rafael Silva, Adley F.Rubira
Publicado por Carbohydrate Polymers, 07/2018

Cellulose nanowhiskers (CWs) extracted from cotton fibers were successfully modified with distinct anhydrides structures and used as additives in poly(vinyl alcohol) (PVA) nanocomposite films. The surface modification of CWs was performed with maleic, succinic, acetic or phthalic anhydride to compare the interaction and action the carboxylic groups into PVA films and how these groups influence in mechanical properties of the nanocomposites. CWs presented a high degree of crystallinity and good dispersion in water, with average length at the nanoscale. The addition of specific amounts (3, 6 and 9 wt.%) of modified-CWs increased up to 4.4 times the storage modulus (PVA88-CWSA 9 wt.%), as observed from dynamic mechanical analysis (DMA), compared to the bare PVA films. A significant increase in mechanical properties such as tensile strength, elastic modulus, and elongation at break showed a close relationship to the amount and chemical surface characteristics of CWs added, suggesting that these modified-CWs could be explored as reinforcement additives in PVA films.

Physical-chemical properties of dental composites and adhesives containing silane-modified SBA-15

Gedalias Custódio Martim; Vicente Lira Kupfer; Murilo Pereira Moisés; Andressa dos Santos; Paulo Henrique Maciel Buzzetti; Andrelson Wellington Rinaldi; Adley Forti Rubira; Emerson Marcelo Girotto
Publicado por Journal of the Mechanical Behavior of Biomedical Materials, 04/2018

The aim of this study was to synthesize and characterize mesoporous materials SBA-15 and SBA-15 modified with 3-(methacryloxy)-propyl-trimethoxysilane (MPS) to be used as inorganic filler in restorative dental composites and adhesives, and evaluate the main physical-chemical properties of the resulting material. The SBA-15 and SBA-15/MPS were characterized by FTIR, BET and X-Ray and combined with TEGDMA, bis-GMA and commercial spherical silica to produce dental composites. Afterwards, the mesoporous materials were combined with TEGDMA, bis-GMA and HEMA to make adhesives. To compare the results, composites and adhesives containing only commercial spherical silica were investigated. Some physical-chemical properties such as degree of conversion (DC), flexural strength (FS) and modulus (FM), water sorption and solubility (Wsp and Wsl), specific area (BET), and the leachable components were evaluated. The SBA-15/MPS can be used to prepare dental restorative materials, with some foreseeable advantages compared with pure SBA-15 dental materials and with improved properties compared with commercial spherical silica dental materials. An important improvement was that the dental materials based on modified SBA-15 presented a reduction of approximately 60% in leaching of unreacted monomers extracted by solvent compared to the control group.

Synthesis, characterization and sorption studies of aromatic compounds by hydrogels of chitosan blended with β-cyclodextrin-and PVA-functionalized pectin

Cesar M. C. Filho, Pedro V. A. Bueno, Alan F. Y. Matsushita, Adley F. Rubira, Edvani C. Muniz, Luísa Durães, Dina M. B. Murtinho, Artur J. M. Valente.
Publicado por RSC Advances, 04/2018

Petroleum comprises the monoaromatic and polycyclic aromatic hydrocarbons, which exhibit acute toxicity towards living animals. Consequently, their removal from natural environment is a priority challenge. On the other hand, biomaterials are increasingly being used as adsorbents. Pectin and chitosan are well-known polysaccharides able to form coacervate hydrogels. Aiming an increase of sorption ability by hydrophobic compounds, pectin was also functionalized with two amphiphilic compounds: β-cyclodextrin (β-CD) and poly(vinyl alcohol) (PVA). Both the modified pectin and the hydrogels were evaluated using nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The hydrogels were further characterized in terms of thermogravimetric analysis (TGA) and swelling kinetics. The interaction between the hydrogel and mix solutions containing six different aromatic compounds (BTXs and the following PAHs: pyrene, benzo(b)fluoranthene and benzo(a)pyrene) has been evaluated through sorption isotherms and kinetics. The mechanism of sorption interaction and the selectivity of the adsorbents towards different aromatic compounds were discussed. The results clearly show that the presence of β-CD and PVA into gel leads to an increase in the removal efficiency of both, BTXs and PAHs. The gels were subjected to two sorption/desorption cycles to have an assessment of the capability of adsorbents for re-use. Finally, the sorption quantification of those six aromatic compounds from a real gasoline sample onto gels has been tested.

Hydrophobization of cashew gum by acetylation mechanism and amphotericin B encapsulation

Mayrla R. Lima; Haroldo C. B. Paula; Flávia O. M. S. Abreu; Rudson B. C. da Silva; Fernanda M. Sombra; Regina C. M. de Paula
Publicado por International Journal of Biological Macromolecules, 03/2018

Cashew gum (GC) is a polysaccharide whose structural modification has the potential to extend its applications on varied fields such as to the formation of self-organized nanoparticulated systems. In this work, a 23 factorial design was carried out, aiming at evaluation of the influence of the reactional parameters of an acetylation reaction on the final properties of cashew gum. The effects of temperature, reaction time and amount of acetylating agent on the reaction yield and degree of GC acetylation were investigated. Data obtained revealed that the aforementioned parameters influenced both yield and degree of acetylation. Statistical analysis showed that the different derivatives had their variables influenced mainly by temperature and interaction effect between the factors time and quantity of acetylating agent. Acetylated derivatives were obtained with yield higher than 90% and degrees of acetylation above 2.42. Data on the formation of self-organized systems, revealed particle sizes in the range 190-300 nm, where smaller particle sizes were obtained for derivatives with acetylation degrees lower than 1.5. Release profiles of Amphotericin-B incorporated in derivative nanoparticles, yielded 70% encapsulation efficiency and long release profiles, corroborating their potential application to delivery of hydrophobic active principles.

Pickering emulsion stabilized by cashew gum- poly-L-lactide copolymer nanoparticles: Synthesis, characterization and amphotericin B encapsulation

A. R. Richter, J. P. A. Feitosa, H. C. B. Paula, F. M. Goycoolea, R. C. M. de Paula
Publicado por Colloids and Surfaces B: Biointerfaces, 04/2018

In this work, we provide proof-of-concept of formation, physical characteristics and potential use as a drug delivery formulation of Pickering emulsions (PE) obtained by a novel method that combines nanoprecipitation with subsequent spontaneous emulsification process. To this end, pre-formed ultra-small (d.∼10 nm) nanoprecipitated nanoparticles of hydrophobic derivatives of cashew tree gum grafted with polylactide (CGPLAP), were conceived to stabilize Pickering emulsions obtained by spontaneous emulsification. These were also loaded with Amphotericin B (AmB), a drug of low oral bioavailability used in the therapy of neglected diseases such as leishmaniasis. The graft reaction was performed in two CG/PLA molar ratio conditions (1:1 and 1:10). Emulsions were prepared by adding the organic phase (Miglyol 812®) in the aqueous phase (nanoprecipitated CGPLAP), resulting the immediate emulsion formation. The isolation by centrifugation does not destabilize or separate the nanoparticles from oil droplets of the PE emulsion. Emulsions with CGPLAP 1:1 presented unimodal distributions at different CGPLA concentration, lower values in size and PDI and the best stability over time. The AmB was incorporated in the emulsions with a process efficiency of 21–47%, as determined by UV–vis. AmB in CGPLAP emulsions is in less aggregated state than observed in commercial AmB formulation.

Nanocellulose nanocomposite hydrogels: technological and environmental issues

Diego M. Nascimento, Yana L. Nunes, Maria C. B. Figueirêdo, Henriette M. C. de Azeredo, Fauze A. Aouada, Judith P. A. Feitosa, Morsyleide F. Rosa, Alain Dufresne
Publicado por Green Chemistry, 04/2018

Over the last decade, nanocellulose-based nanocomposite hydrogels have emerged as promising materials in different fields of application such as medicine, food, and agriculture. The present review addresses the advances in the synthesis methods and technological applications of these hydrogels. Different chemical and physical cross-linking methods used for the design of cellulose nanocrystals, cellulose nanofibrils, and bacterial cellulose hydrogels are discussed in detail. Nanocomposite hydrogels based on nanocellulose or reinforced with nanocellulose have good mechanical properties, biocompatibility, and biodegradability and allow the incorporation of several molecules or solutes, which can provide a slow and controlled release profile. The major advances exploring these hydrogels in biomedicine, food, and agriculture are reviewed. Finally, challenges and environmental issues related to their production are briefly discussed.


Laura Caetano Escobar da Silva, Luiz Guilherme L. Germiniani, Tomás S. Plivelic & Maria do Carmo Gonçalves
Publicado por Soft Matter, 03/2018

Biocompatible chemically cross-linked organic–inorganic (O–I) hybrid nanocomposites were developed using a new atoxic, simple and fast, solvent-free pathway. Poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG), which are both biocompatible, were used as the organic moieties (at different PCL/PEG ratios), while in situ synthesized polysilsesquioxanes made up the inorganic moiety. The O–I hybrid nanocomposites’ molecular structures were characterized using solid-state 29Si NMR, TGA and ATR-IR. Results showed an unusually high condensation yield of approximately 90% and two distinct silsesquioxane structures. No traces of the remaining isocyanate groups were found. Advanced morphological characterization of the ternary O–I hybrids was performed using a combination of electron microscopy and X-ray scattering techniques such as SEM, TEM, ESI-TEM, WAXS and temperature-dependent SAXS. Results showed the occurrence of spherical nanoparticles, associated with polysilsesquioxane, and ordered network grains, associated with PCL and/or PEG chains cross-linked by silsesquioxane cages. As a consequence, a four-phased nanostructured morphology was proposed. In this model, PCL and PEG are undistinguishable, while polysilsesquioxane nanoparticles are uniformly distributed throughout a homogeneous cross-linked matrix, which shows gel-like behavior. Moreover, a mobile phase made up of unbound polymer chains occurs at the grain interface.

From aqueous dispersion to functional materials: capillarity and electrostatic adhesion

Fernando Galembeck
Publicado por The Chemical Record, 02/2018

The author was first acquainted with polymer lattices as model particles for studying sedimentation phenomena, evolving towards the elucidation of synthetic and natural latex heterogeneity and microchemistry. This brought new elements to understand the remarkable mechanical properties of natural rubber, leading to the latex route for making nanocomposites. These materials show exceptional properties that are largely due to electrostatic adhesion, a concept that had been previously presented by Deryagin but was later abandoned. Electrostatic adhesion is the outcome of ion partition and self‐assembly within drying aqueous dispersions, producing co‐existing domains with opposite charges. Their examination allowed several experimental observations leading to the proposal of mechanisms to explain hitherto challenging electrostatic phenomena shown by solids and liquids. Water plays a decisive role in all the different phenomena described in this account.

Hydrofluoric acid concentrations: Effect on the cyclic load-to-failure of machined lithium disilicate restorations

Catina Prochnow, Andressa Borin Venturini, Luís Felipe Guilardi, Gabriel Kalil Rocha Pereira, Thiago Augusto Lima Burgo, Marco Cícero Bottino, Cornelis Johannes Kleverlaan, Luiz Felipe Valandro
Publicado por Dental Materials, 09/2018

Objectives: To evaluate the effects of the etching with different hydrofluoric acid (HF) concentrations on the cyclic load-to-failure of machined lithium disilicate crowns cemented to dentin analogue material. Methods: Pairs of dentin analogue prosthetic preparations and lithium disilicate ceramic crowns with simplified and standardized designs were machined (n = 18). The preparations were etched with 10% HF (60 s), followed by primer application. The intaglio surface of the ceramic crowns was treated as follows: non-etched (control, CTRL); or etched for 20 s with different HF concentrations — 3% (HF3), or 5% (HF5), or 10% (HF10). A silane coating was then applied onto the treated ceramic surfaces, and they were adhesively cemented to the preparations. To perform the fatigue tests (staircase approach), a hemispheric stainless-steel piston (Ø = 40 mm) applied cyclic loads in the center of the crowns under water (initial load: 720 N; step-size: 70 N; cycles: 500,000; frequency: 20 Hz). Additionally, topographic, fractographic, and fractal analyses were carried out. The fatigue data were analyzed using the Dixon and Mood method. Results: Although the topographic and fractal analyses depicted the action of HF etching altering the superficial complexity and topography, the preponderant topography pattern was established by machining on CAD/CAM. All groups showed similar CLf (in N) (CTRL = 805.00 ± 91.23; HF3 = 781.25 ± 29.87; HF5 = 755.00 ± 154.49; HF10 = 833.75 ± 100.74). Significance: Etching with different HF acid concentrations did not promote a deleterious effect on the cyclic load-to-failure of machined lithium disilicate crowns.

Towards superlubricity in nanostructured surfaces: the role of van der Waals forces

Fernando G. Echeverrigaray, Saron R. S. de Mello, Leonardo M. Leidens, Marcelo E. H. Maia da Costa, Fernando Alvarez, Thiago A. L. Burgo, Alexandre F. Michels and Carlos A. Figueroa
Publicado por Physical Chemistry Chemical Physics, 07/2018

Hydrogenated amorphous carbon (a-C:H) thin films have a unique combination of properties that are fundamental in mechanical and electromechanical devices aimed at energy efficiency issues. The literature brings a wealth of information about the ultra-low friction (superlubricity) mechanism in a-C:H thin films. However, there is persistent controversy concerning the physicochemical mechanisms of contact mechanics at the atomic/molecular level and the role of electrical interactions at the sliding interface is still a matter of debate. We find that the hydrogenation of the outermost nanostructured surface atomic layers of a-C:H thin films is proportional to the surface potential and also to the friction forces arising at the sliding interface. A higher hydrogen-to-carbon ratio reduces the surface potential, directly affecting frictional forces by a less effective long-term interaction. The structural ultra-low friction (superlubricity) is attributed to a lower polarizability at the outermost nanostructured layer of a-C:H thin films due to a higher hydrogen density, which renders weaker van der Waals forces, in particular London dispersion forces. More hydrogenated nanodomains at the surface of a-C:H thin films are proposed to be used to tailor superlubricity.

Influence of Carboxylic Acids on Poly(lactic acid)/Thermoplastic Starch Biodegradable Sheets Produced by Calendering–Extrusion

Marianne Ayumi Shirai, Juliano Zanela, Marcos Hiroiuqui Kunita, Guilherme Miranda Pereira, Adley Forti Rubira, Carmen Maria Olivera Müller, Maria Victória Eiras Grossmann and Fabio Yamashita
Publicado por Advances in Polymer Technology, 03/2018

Sheets of poly(lactic acid) (PLA) and thermoplastic starch (TPS) with citric and adipic acid additives were produced through a calendering–extrusion process at pilot scale, and its mechanical, barrier, thermal, and morphological characteristics were determined. According to the micrographs, citric acid improved the fragmentation and dispersion of starch granules by facilitating interactions with PLA chains and increasing interfacial adhesion. Citric acid also induced a significant increase in the tensile strength and elongation at break, reducing water vapor permeability, increasing crystallinity, but decreased slightly the thermal stability. Adipic acid did not demonstrate the same efficiency, even when mixed with citric acid.

Cellulose nanowhiskers decorated with silver nanoparticles as an additive to antibacterial polymers membranes fabricated by electrospinning

Cristiane Spagnol, Elizângela H. Fragal, Antonio G. B. Pereira, Celso V. Nakamura, Edvani C. Muniz, Heveline D. M. Follmann, Rafael Silva and Adley F. Rubira
Publicado por Journal of Colloid and Interface Science, 12/2018

Antimicrobial films based on distinct polymer matrices, poly (vinyl alcohol) (PVA) or poly (N-isopropylacrylamide) (PNIPAAm), and silver nanoparticles (AgNPs) immobilized onto cellulose nanowhiskers (CWs) were successfully prepared by either casting or electrospinning. CWs were first functionalized with carboxylate groups (labeled as CWSAc) and later they were immersed in a silver nitrate solution (AgNO3). After Ag+ ions anchored in the COO groups are chemically reduced to produce AgNPs. The CWSAc/AgNPs biological activity was evaluated against Staphylococcus aureus (S. aureus), Bacillus Subtilis (B. subtilis), Escherichia coli (E. coli), and Candida albicans (C. albicans). The materials were more effective against C. albicans that showed a MIC of 15.6 µg/mL. In the process of AgNPs synthesis, the activity of the stabilizing agent (gelatin) and concentration of precursor and reducing agents were evaluated. The synthesized polymeric films displayed good antimicrobial activity against S. aureus, E. coli, and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The PVA films with CWSAc/AgNPs showed diameter of the inhibition halo of up to 11 mm. The results obtained displayed that the films obtained have a potential application to be used in different fields such as packaging, membrane filtration, wound dressing, clothing and in different biomedical applications.

Chitosan-based hydrogels: From preparation to biomedical applications

Michelly C. G. Pellá, Michele K. Lima-Tenório, Ernandes T. Tenório-Neto, Marcos R. Guilherme, Edvani C. Muniza, Adley F. Rubira
Publicado por Carbohydrate Polymers, 09/2018

The advances in the field of biomaterials have led to several studies on alternative biocompatible devices and to their development focusing on their properties, benefits, limitations, and utilization of alternative resources. Due to their advantages like biocompatibility, biodegradability, and low cost, polysaccharides have been widely used in the development of hydrogels. Among the polysaccharides studied on hydrogels preparation, chitosan (pure or combined with natural/synthetic polymers) have been widely investigated for use in biomedical field. In view of potential applications of chitosan-based hydrogels, this review focuses on the most recent progress made with respect to preparation, properties, and their salient accomplishments for drug delivery and tissue engineering.

pH-responsive alginate-based hydrogels for protein delivery

Diego S. Lima, Ernandes T. Tenório-Neto, Michele K. Lima-Tenório, Marcos R. Guilherme, Débora B. Scariot, Celso V. Nakamura, Edvani C. Muniz and Adley F. Rubira
Publicado por Journal of Molecular Liquids, 07/2018

This work describes the synthesis and characterization of pH-responsive hydrogels based on alginate for protein delivery. Synthesis approach shown here has included the modification of sodium alginate to convert it into a covalently crosslinkable polysaccharide and the subsequent radical polymerization reaction with sodium acrylate and N-vinylpyrrolidone for hydrogelation. To evaluate the applicability of the obtained hydrogels as an oral protein delivery system, we studied the cytotoxicity, the drug release profile (using BSA as a protein model), and the swelling performance in the basic and acidic environments. The hydrogels showed a pH-dependent swelling profile with higher value at pH 7.4. The protein release mechanism was demonstrated to be dependent on pH and composition. The proposed materials were shown to be compatible with living cells, indicating great pharmacological potential. These results show that the hydrogels are ideally suited for use as an oral drug delivery device.

Water Droplet Self-Assembly to Au Nanoporous Films with Special Light Trapping and Surface Electromagnetic Field Enhancement

Vanessa H. Fragal, Elizângela H. Fragal, Adley F. Rubira and Rafael Silva
Publicado por Langmuir, 11/2018

Gold nano “breath figure” films are for the first time reported and their function as ideal systems for plasmonics demonstrated. Metal nano-breath figure substrates are metal thin films containing nanohole arrays supported on a solid substrate. Au nanohole arrays are prepared from the dynamic breath figure phenomenon, in which the pore formation is controlled to provide holes smaller than 100 nm. Au layer is deposited on polymer substrates containing breath figure topology. The breath figure topology can be fully translated to the Au layer. The nanofabrication process is completed within few minutes. A simplified preparation process but very impressive light trapping and surface electromagnetic field enhancement are related to the Au breath figure films obtained in this work. The porous films demonstrated higher absorbance in the region of 500–1100 nm than nonporous Au films. In the case of 10 nm Au film, the plasmon absorbance becomes more intense than the electronic band absorbance. The electromagnetic enhancement is proved by surface enhanced Raman spectroscopy effect, which is found to be very close to the maximum possible value predicted for nonresonant species.

In vitro anti-Leishmania activity of T6 synthetic compound encapsulated in yeast-derived β-(1,3)-D-glucan particles

Hélito Volpato, Débora Botura Scariot, Edna Filipa Pais Soares, Andrey Petita Jacomini, Fernanda Andreia Rosa, Maria Helena Sarragiotto, Tânia Ueda-Nakamura, Adley Forti Rubira, Guilherme Miranda Pereira, Rui Manadas, Alcino J. Leitão, Olga Borges, Celso Vataru Nakamura, Maria do Céu Sousa
Publicado por International Journal of Biological Macromolecules, 11/2018

The objective of this study was to encapsulate a synthetic compound, the 4-[(2E)-N′-(2,2′-bithienyl-5-methylene)hydra-zinecarbonyl]-6,7-dihydro-1-phenyl-1H-pyrazolo[3,4-d]pyridazin-7-one (T6) in glucan-rich particles mainly composed by the cell wall of Saccharomyces cerevisiae (GPs) and to study their individual and combined activity on Leishmania infantum. The possible mechanism of action of T6 was also investigated. Our results showed the activity of T6 compound in both promastigote (IC50 = 2.5 μg/mL) and intracellular amastigote (IC50 = 1.23 μg/mL) forms. We also found activity against intracellular amastigote forms (IC50 = 8.20 μg/mL) when the T6 compound was encapsulated in GPs. Another interesting finding was the fact that T6 encapsulated in GPs showed a significant decrease in J774A1 macrophage toxicity (CC50 ≥ 18.53 μg/mL) compared to the T6 compound alone (IC50 = 2.27 μg/mL). Through electron microscopy and biochemical methodologies, we verified that the activity of T6 in promastigote forms of L. infantum was characterized by events of cell death by apoptosis like increased ROS production, cell shrinkage, phosphatidylserine exposure and DNA fragmentation. We conclude that T6 can be considered a promising anti-Leishmania compound, and that the use of GPs for drug encapsulation is an interesting approach to the development of new effective and less toxic formulations.

Bionanocomposites based on mesoporous silica and alginate for enhanced drug delivery

Hugo H. C. de Lima, Vicente L. Kupfer, Murilo P. Moisés, Marcos R. Guilherme, Jaqueline de C. Rinaldi, Sérgio L. Felisbino, Adley F. Rubira, Andrelson W. Rinaldi
Publicado por Carbohydrate Polymers, 09/2018

This work reports the preparation, the characterization and the prednisolone release profile of biocompatible hydrogel nanocomposites containing mesoporous silica (SBA) and alginate as a biomaterial for enhanced drug delivery with reduced burst effect and improved mechanical properties. Such systems, which were prepared using specific SBA/alginate-crosslinking chemistry, exhibited interconnecting pore hybrid network owing to both mesoporous silica and hydrogel characteristics. Activated SBA was shown to be a determinant factor in inhibiting initial burst by nearly 90% and the drug was released with minimal burst kinetics. The nanoparticles reduced the movements of polymer chains, affecting macromolecular relaxation, and the distribution of mesoporous silica within the hydrogel made drug release into surrounding liquid less favorable. The proposed systems are biocompatible with human immortalized RWPE-1 prostatic epithelial cells. This report offers an approach of up-to-date interest for the development of advanced biomaterials for further physiological and pathological applications.

Conversion of “Waste Plastic” into Photocatalytic Nanofoams for Environmental Remediation

Geovania C. de Assis, Euzébio Skovroinski, Valderi D. Leite, Marcelo O. Rodrigues, André Galembeck, Mary C. F. Alves, Julian Eastoe and Rodrigo J. de Oliveira
Publicado por ACS Applied Materials & Interfaces, 02/2018

Plastic debris is a major environmental concern, and to find effective ways to reuse polystyrene (PS) presents major challenges. Here, it is demonstrated that polystyrene foams impregnated with SnO2 are easily generated from plastic debris and can be applied to photocatalytic degradation of dyes. SnO2 nanoparticles were synthesized by a polymeric precursor method, yielding specific surface areas of 15 m2/g after heat treatment to 700 °C. Crystallinity, size, and shape of the SnO2 particles were assessed by X-ray diffraction (XRD) and transmission electron microscopy (TEM), demonstrating the preparation of crystalline spherical nanoparticles with sizes around 20 nm. When incorporated into PS foams, which were generated using a thermally induced phase separation (TIPS) process, the specific surface area increased to 48 m2/g. These PS/SnO2 nanofoams showed very good efficiency for photodegradation of rhodamine B, under UV irradiation, achieving up to 98.2% removal. In addition the PS/SnO2 nanofoams are shown to retain photocatalytic activity for up to five reuse cycles.

In Vitro morphological, optical and microbiological evaluation of nanosilver fluoride in the remineralization of deciduous teeth enamel

Amitis Vieira Costa e Silva, Joás Araújo Teixeira, Cláudia C. B. O. Mota, Emery Clayton Cabral Correia Lins, Paulo Correia de Melo Júnior, Maria Goretti de Souza Lima, Manuela Arnaud, André Galembeck, Andrea Targino Gadelha, José Ricardo Dias Pereira, Anderson S. L. Gomes, Aronita Rosenblatt
Publicado por Nanotechnology Reviews, 11/2018

Background: Nanosilver fluoride (NSF) was developed as an alternative in the prevention of dental caries. Purpose: The aim of this study was to test the remineralizing action of NSF on incipient enamel caries and its antimicrobial action on the acid production and adhesion of Streptococcus mutans. Methods: Deciduous enamel fragments were treated with sodium fluoride (NaF), NSF and deionized water. Microhardness, fluorescence spectroscopy and optical coherence tomography imaging were performed on each specimen before chemical caries induction, after caries induction and after 14 days of pH cycling. The treated enamel fragments were also placed into test tubes containing bacterial suspension and saliva. The pH readings and quantification of the adhered microorganisms to the dental enamel were determined. Analysis of variance, Kruskal-Wallis, Mann-Whitney, Tukey and mixed linear regression model were applied. Results: NSF and NaF were effective in enamel remineralization, with a statistically significant difference (p<0.001) to deionized water, and they had no statistically significant difference between themselves (p>0.005). NSF had greater effectiveness compared to NaF in preventing decreases of pH and adhesion of S. mutans to the enamel surface, with statistically significant (p<0.001) differences. Conclusion: NSF may be more effective than conventional fluorides in treating incipient caries lesions due to its remineralization and antibacterial actions.

Highly Conducting, Sustainable, Nanographitic Rubber Composites

Katerina Kampioti, Carolina F. Matos, Fernando Galembeck, Christèle Jaillet, Alain Derré, Aldo J. G. Zarbin and Alain Pénicaud
Publicado por ACS Omega, 02/2018

Environmentally friendly multifunctional rubber composites are reported. Graphitic nanocarbon (NC) deriving from cracking of biogas (methane/carbon dioxide) and natural rubber extracted directly from the Hevea brasiliensis tree are the two components of these composites produced via latex technology. While maintaining and enhancing the intrinsic thermal and mechanical characteristics of rubber, the presence of NC shows a significant improvement on the electrical response. For a 10 wt % NC content, a 1010-fold increase in conductivity has been achieved with a conductivity value of 7.5 S·m–1, placing these composites among the best obtained using other carbon fillers. In addition, the piezoresistive behavior has also been verified. These promising green composites have a potential use in a variety of applications such as sealing of electronic devices and sensors.

Rubber Surface Change and Static Charging under Periodic Stress

Leandra P. Santos, Yan A. S. Campo, Douglas S. da Silva, Thiago A. L. Burgo and Fernando Galembeck
Publicado por Colloids and Interfaces, 11/2018

Rubber materials play an important role in robotics, due to their sensing and actuating abilities, that are exploited in soft smart materials endowed with shape-adaptive and electroadhesive properties. The application of an electric field produces non-linear deformation that has been extensively modelled, but is not understood at the molecular level. The symmetric effect (the production of an electric field due to rubber deformation) was recently discovered and explained as follows: rubber surface chemical composition and adsorptive properties change during rubber deformation, allowing the surface to exchange charge with the atmosphere. The present work describes the complex surface morphology and microchemistry of tubing made from vulcanized natural rubber, showing that it is rough and made from two domain types: stiffer elevations containing Br or Al (depending on the sample used) and O, that rise above an elastic base that is exempt of elements other than C and H. The surface area fraction occupied by the elastic base is higher in the strained rubber than when it is relaxed. Electrostatic potential on rubber surfaces was measured as a function of the stretching frequency, using Kelvin electrodes and showing frequency-dependent potential variation. This is explained considering charge exchange between the atmosphere and rubber surface, mediated by water vapor adsorbed in the stretched rubber and trapped when it relaxes.

Synergy in food, energy and advanced materials production from biomass

Fernando Galembeck
Publicado por Pure and Applied Chemistry, 09/2018

Biomass is a sustainable alternative to fossil fuels, as a source of energy and raw materials for industry. However, this is often criticized, based on an alleged competition with food production due to the presumed scarcity of agricultural land. Data from Brazil and Ethiopia show that the creation and dissemination of new agricultural technology actually allows a significant increase in the production of food as well as energy and raw materials from biomass, bringing economic, social and environmental benefits. Moreover, polymers from biomass display unique features that make them suitable as the basis for making advanced materials, with desirable combinations of chemical and physical properties required for some applications. For instance, natural rubber and cellulose have been used to create new complex nanostructured solids capable of performing new functions. Biomass can thus be exploited as a source of new materials as well as petrochemical-like building blocks.

Effect of clay minerals structure on the polymer flame retardancy intumescent process

Simone Pereira da SilvaRibeiro, Leonardo dos Santos Cescon, Rodrigo Quilelli Correa Rocha Ribeiro, Alexandre Landesmann, Luciana Rocha de Moura Estevão, Regina Sandra Veiga Nascimento
Publicado por Applied Clay Science, 09/2018

This study aimed at investigating the influence of the crystalline structure of a series of clay minerals on the flame retardancy of ethylene based polymer materials with and without an intumescent formulation. The clay minerals tested were mica, kaolinite (Kaol) and palygorskite (Pal). K-feldspar (K-Fsp) was also tested. The intumescent formulation used was composed of ammonium polyphosphate (APP) and pentaerythritol (PER). The flammability was evaluated using UL-94 classification, limiting oxygen index (LOI) and cone calorimeter analyses. The addition of Pal to the intumescent formulation led to the highest LOI value and a rate of heat release (RHR) close to zero, indicating that a great synergy occurred from the interaction of this clay mineral crystalline structure with the polymer chains and the intumescent formulation. The K-Fsp showed the lowest performance. The TGA and heating microscopy analyses showed that the addition of mica, Kaol or Pal led to the formation of a more thermally stable intumescent layer, and the crystalline structure of the clay minerals' appears to affect the synergy with APP/PER. The presence of the tetrahedral SiO4 sheets on both sides of the interlayer space, as in the mica structure, or in the internal face of the channels, as in the Pal, seems to lead to a greater synergistic action.

Cationic starch derivatives as reactive shale inhibitors for water‐based drilling fluids

Leonardo dos Santos Cescon, Priscila Quartarone, Simone Pereira da Silva Ribeiro, Regina Sandra Veiga Nascimento
Publicado por Journal of Applied Polymer Science, 05/2018

One of the major problems associated with the use of water‐based drilling fluids is the interaction of water with specific rock formations, such as shales, and the consequent swelling of reactive clays that may be present in that type of rock. Several types of clays reactivity inhibitors have been used by the oil industry, and the most effective ones are the cationic polyelectrolytes, such as the poly(diallyldimethylammonium chloride) (PDADMAC). However, this polyelectrolyte is very toxic. In this work, a series of cationic starch derivatives with different cationic degrees were synthesized with the objective of evaluating their potential as environmentally correct shale reactivity inhibitors. The results showed that the synthesized derivatives presented a good capacity of adsorption on bentonite and an efficient inhibition of the shale reactivity. The derivative with an intermediate cationic degree presented the best performance. In the tests with the formulated fluids this derivative provided an intact cuttings recovery of 84.8% and a total recovery of 92.3%. These values are very close to those found for the PDADMAC additive, therefore indicating that this cationic starch derivative presents a good potential as inhibitor of the shale reactivity.

Template conversion of MoO3 to MoS2 nanoribbons: synthesis and electrochemical properties

Luciana Vieira, Jose de Ribamar Martins Neto, Odair Pastor Ferreira, Roberto Manuel Torresi, Susana Ines Cordoba de Torresi and Oswaldo Luiz Alves
Publicado por RSC Advances, 08/2018

Hydrothermally synthesized α-MoO3 nanoribbons were converted to MoS2 whilst retaining the same morphology by a solid–gas reaction at 800 °C in a H2S/H2/N2 atmosphere. In order to keep the nanoribbon morphology from the oxide in the sulfide, it was crucial to have a H2S stream during the whole heating process. Thereby, the first layer of sulfide is formed as soon as the oxide is activated avoiding coalescence of the nanoribbons. Afterwards, the sulfidization takes place from the outer shell to the inner core of the nanoparticles. Both α-MoO3 and MoS2-NR were investigated for the electrochemical intercalation of lithium-ions. The electrochemical insertion and removal of lithium in the molybdenum oxide are accompanied by a change of color, which was measured by in situ UV-Vis. Spectroelectrochemical experiments showed a distinguished electrochromic behavior with a significant potential-dependent change in absorbance at 660 nm upon Li+ insertion. Analysis of in situ voltammetry revealed the presence of three active sites for lithium insertion in the MoO3-NRs, which are accompanied by only two chromophores in the same potential range. Voltammetric measurements of the MoS2 nanoribbons presented a reversible reduction of MoS2 to LixMoS2, followed by Mo and Li2S, which can be further reduced to Li and S at more negative potentials. Such sulfide materials are highly promising for lithium batteries. This template synthesis is a simple method to obtain high purity MoS2 nanoparticles with a controlled morphology of nanoribbons.

Microwave-assisted synthesis of palladium nanoparticles intercalated nitrogen doped reduced graphene oxide and their electrocatalytic activity for direct-ethanol fuel cells

Rajesh Kumar, Everson T. S. G. da Silva, Rajesh K. Singh, Raluca Savu, Andrei V. Alaferdov, Leandro C. Fonseca, Lory C. Carossi, Arvind Singh, Sarita Khandka, Kamal K. Kar, Oswaldo L. Alves, Lauro T. Kubota, Stanislav A.Moshkalev
Publicado por Journal of Colloids and Interface Science, 04/2018

Palladium nanoparticles decorated reduced graphene oxide (Pd-rGO) and palladium nanoparticles intercalated inside nitrogen doped reduced graphene oxide (Pd-NrGO) hybrids have been synthesized by applying a very simple, fast and economic route using microwave-assisted in-situ reduction and exfoliation method. The Pd-NrGO hybrids materials show good activity as catalyst for ethanol electro oxidation for direct ethanol fuel cells (DEFCs) as compared to Pd-rGO hybrids. The enhanced direct ethanol fuel cell can serve as alternative to fossil fuels because it is renewable and environmentally-friendly with a high energy conversion efficiency and low pollutant emission. As proof of concept, the electrocatalytic activity of Pd-NrGO hybrid material was accessed by cyclic voltammetry in presence of ethanol to evaluate its applicability in direct-ethanol fuel cells (DEFCs). The Pd-NrGO catalyst presented higher electro active surface area (∼6.3 m2 g−1) for ethanol electro-oxidation when compared to Pd-rGO hybrids (∼3.7 m2 g−1). Despite the smaller catalytic activity of Pd-NrGO, which was attributed to the lower exfoliation rate of this material in relation to the Pd-rGO, Pd-NrGO showed to be very promising and its catalytic activity can be further improved by tuning the synthesis parameters to increase the exfoliation rate.

Chemically cross-linked aerogels based on cellulose nanocrystals and polysilsesquioxane

Daniela de Morais Zanata, Liliane Cristina Battirola, Maria do Carmo Gonçalves
Publicado por Cellulose, 12/2018

In this work, we report one-pot synthesis of free standing and porous hybrid cross-linked aerogels based on cellulose nanocrystals (CNCs) and polysilsesquioxane (PSS). The synthesis of the aerogel was carried out in two steps. The first was CNC surface modification, using a 3-isocyanatopropyltriethoxysilane, and the second, a sol–gel process, resulting in the formation of a PSS network which cross-linked with the nanoparticles. 29Si solid state NMR analysis revealed that this network was mostly made up of linear and three-dimensional PSS domains. Aerogels showed shape stability and high porosity (> 89%). The presence of macro and mesopores was confirmed by SEM and BET analyses, respectively, and the presence of the PSS network domains in the pore walls was characterized by TEM. In addition, these CNC/PSS aerogels were omniphilic, absorbing approximately the same amount of both water and toluene. These characteristics make these aerogels interesting material to be used as absorbents for a wide variety of spills.

A multistep mild process for preparation of nanocellulose from orange bagasse

Mayra A. Mariño, Camila A. Rezende, Ljubica Tasic
Publicado por Cellulose, 08/2018

Orange bagasse in natura and industrial orange bagasse were investigated as starting materials for the production of nanocellulose under moderate chemical sequential extraction conditions. The latter accounted for acid (5% v v−1 and 100 °C) and/or alkaline conditions (NaOH 1.6–4.0% m v−1, 120 °C); and bleaching with NaClO2 (1–3% m v−1, 80 °C). Ultrasound treatment yielded very similar cellulose nanofibers with 60–70% of crystallinity and highly pure (over 98%). As seen by field emission scanning electron microscopy, cellulose nanofibers showed mean diameters of 18.4 nm ± 6.0 nm from bagasse in natura, while 20.5 nm ± 7.0 nm mean diameters were observed for the nanofibers isolated from the industrial bagasse. Crystallinity indices were determined using X-ray diffraction and solid-state nuclear magnetic resonance (CP–MAS 13C NMR) data. The obtained materials have numerous potential applications and represent a green alternative for the treatment of orange fruit biomass.

Mechanochemical transduction and hygroelectricity in periodically stretched rubber

Leandra P. Santos, Douglas S. da Silva, Bruno C. Batista, Kelly S. Moreira, Thiago A. L. Burgo and Fernando Galembeck
Publicado por Polymer, 05/2019

This work reports the rubber electrostatic potential due to repeated strain as a function of time for periods as long as the lifetime of the sample. Rubber potential depends on two main contributions: hygroelectricity added to the mechanochemical reactions evidenced by spectroscopy and microscopy/microanalytical experiments. Hygroelectricity produces fast periodic charging in phase with rubber strain, while a slower charging process is assigned to the mechanochemical reaction products, in conjunction with residual hygroelectricity. This result explains the significant negative potential displayed by rubber over long periods in the absence of any external applied voltage. These findings may contribute to improving dielectric elastomer performance in many applications that are currently of great interest in robotics and energy harvesting. Additionally, electric potential real-time measurements show desirable features as a tool for real-time, non-contact detection of rubber structural change and fatigue.

Conduction and Excess Charge in Silicate Glass/Air Interfaces

Victor T. C. Paiva, Leandra P. Santos, Douglas S. da Silva, Thiago A. L. Burgo and Fernando Galembeck
Publicado por Langmuir, 05/2019

The glass/air interface shows electrical properties that are unexpected for a widely used electrical insulator. The mobility of interfacial charge carriers under 80% relative humidity (RH) is 4.81 × 10–5 m2 s–1 V–1, 3 orders of magnitude higher than the electrophoretic mobility of simple ions in water and less than 2 orders of magnitude lower than the electron mobility in copper metal. This allows the glass/air interface to reach the same potential as a biased contacting metal quickly. The interfacial surface resistance R increases by more than 5 orders of magnitude when the RH decreases from 80 to 2%, following an S-shaped curve with small hysteresis. Moreover, the biased surfaces store charge, as shown by Kelvin potential measurements. Applying an electric field parallel to the surface produces RH-dependent results: under low humidity, the interface behaves as expected for an ideal two-dimensional parallel-plate capacitor, while under high RH, it acquires and maintains excess negative charge, which is lost under low RH. The glass surface morphology and potential distribution change on the glass/air interface under high RH and applied potential, including the extensive elimination of nonglass contaminating particles and potential levelling. All these surprising results are explained by using a protonic-charge-transfer mechanism: mobile protons dissociated from silanol groups migrate rapidly along a field-oriented adsorbed water layer, while the matrix-bound silicate anions remain immobile. Glass may thus be classified as the ionic analogue of a topological insulator but based on structural features and charge-transfer mechanisms different from the chalcogenides that have been receiving great attention in the literature.

Polysaccharide-based adsorbents prepared in ionic liquid with high performance for removing Pb(II) from aqueous systems

Késsily B. Rufato, Vitor C. Almeida, Matt J. Kipper, Adley F. Rubira, Alessandro F. Martins, Edvani C. Muniz
Publicado por Carbohydrate Polymers, 07/2019

Alginate/chitosan (ALG/CHT) and alginate/N,N-dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO4]). The [Hmim][HSO4] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (qm) of 529.4 mg g−1 and 560.2 mg g−1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO4] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO4] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents.

Multifunctional coatings of exfoliated and reassembled graphite on cellulosic substrates

Leandra Pereira dos Santos, Douglas Soares da Silva, Joao Paulo Ferreira Bertacchi, Kelly Schneider Moreira, Thiago Augusto de Lima Burgo, Bruno Batista, Jeferson dos Santos, Patrick Alvarenga de Paula and Fernando Galembeck
Publicado por Faraday Discussions, 02/2020

Graphite is spontaneously exfoliated within aqueous alkaline cellulose solutions, forming stable dispersions that can be used to coat cellulosic, ceramic and other substrates with continuous macroscopic layers. These are stable under various conditions and adhere strongly to wood, paper, cardboard, fabric, charcoal and brick. Coating morphology changes from highly smooth to porous and rough, depending on the coat finishing procedure used. Coated paper sheets perform as leads in electric circuitry and as electrodes in electrodeposition, supercapacitors, hygroelectricity cells and other electrochemical devices. Exfoliated and reassembled graphite (ERG) coatings also show low-friction, low-adhesion properties and they prevent fire propagation. This unique combination of properties is explained as a consequence of singular features of cellulose that allow it to play various roles during ERG fabrication and use as an exfoliant, dispersant, stabilizer and adhesive.

Activity and Cell-Death Pathway in Leishmania infantum Induced by Sugiol: Vectorization Using Yeast Cell Wall Particles Obtained From Saccharomyces cerevisiae

D.B. Scariot, H. Volpato, N.S. Fernandes, E.F.P. Soares, T. Ueda-Nakamura, B.P. Dias-Filho, Z. Ud Din, E. Rodrigues-Filho, A.F. Rubira, O. Borges, M. do Céu Souza, C.V. Nakamura
Publicado por Frontiers in Cellular and Infection Microbiology, 06/2019

Visceral leishmaniasis, caused by Leishmania infantum, is a neglected tropical disease, to which efforts in the innovation of effective and affordable treatments remain limited, despite the rising incidence in several regions of the world. In this work, the antileishmanial effects of sugiol were investigated in vitro. This compound was isolated from the bark of Cupressus lusitanica and showed promising activity against L. infantum. In spite of the positive results, it is known that the compound is a poorly water-soluble diterpene molecule, which hinders further investigation, especially in preclinical animal studies. Thus, in an alternative delivery method, sugiol was entrapped in glucan-rich particles obtained from Saccharomyces cerevisiae yeast cell walls (YCWPs). To evaluate the activity of sugiol, the experiments were divided into two parts: (i) the in vitro investigation of antileishmanial activity of free sugiol against L. infantum promastigotes after 24, 48, and 72 h of treatment and (ii) the evaluation of antileishmanial activity of sugiol entrapped in glucan-rich particles against intracellular L. infantum amastigotes. Free sugiol induced the cell-death process in promastigotes, which was triggered by enhancing cytosolic calcium level and promoting the autophagy up to the first 24 h. Over time, the presence of autophagic vacuoles became rarer, especially after treatment with lower concentrations of sugiol, but other cellular events intensified, like ROS production, cell shrinkage, and phosphatidylserine exposure. Hyperpolarization of mitochondrial membrane potential was found at 72 h, induced by the mitochondria calcium uptake, causing an increase in ROS production and lipid peroxidation as a consequence. These events resulted in the cell death of promastigotes by secondary necrosis. Sugiol entrapped in glucan-rich particles was specifically recognized by dectin-1 receptor on the plasma membrane of macrophages, the main host cell of Leishmania spp. Electron micrographs revealed particles containing sugiol within the infected macrophages and these particles were active against the intracellular L. infantum amastigotes without affecting the host cell. Therefore, the YCWPs act like a Trojan horse to successfully deliver sugiol into the macrophage, presenting an interesting strategy to deliver water-insoluble drugs to parasitized cells.

Deriving Efficient Porous Heteroatom‐Doped Carbon Electrocatalysts for Hydrazine Oxidation from Transition Metal Ions‐Coordinated Casein

Vanessa H. Fragal, Elizângela H. Fragal, Tao Zhang, Xiaoxi Huang, Thelma S. P. Cellet, Guilherme M. Pereira, Andrei Jitianu, Adley F. Rubira, Rafael Silva and Tewodros Asefa
Publicado por Advanced Functional Materials, 01/2019

In this work, the synthesis of high‐performance, metal ion‐imprinted, mesoporous carbon electrocatalysts for hydrazine oxidation reaction (HzOR) using casein or a family of phosphoproteins derived from cow's milk as a precursor is shown. The synthesis is made possible by mixing trace amounts of non‐noble metal ions (Fe3+ or Co2+) with casein and then producing different metal ions‐functionalized casein intermediates, which upon carbonization, followed by acid treatment, lead to metal ion‐imprinted catalytically active sites on the materials. The materials effectively electrocatalyze HzOR with low overpotentials at neutral pH and exhibit among the highest electrocatalytic performances ever reported for carbon catalysts. Their catalytic activities are also better than the corresponding control material, synthesized by carbonization of pure casein and other materials previously reported for HzOR. This work demonstrates a novel synthetic route that transforms an inexpensive protein to highly active carbon‐based electrocatalysts by modifying its surfaces with trace amounts of non‐noble metals. The types of metal ions employed in the synthesis are found to dictate the electrocatalytic activities of the materials. Notably, Fe3+ is found to be more effective than Co2+ in helping the conversion of casein into more electrocatalytically active carbon materials for HzOR.

In vitro immunotoxicological assessment of a potent microbicidal nanocomposite based on graphene oxide and silver nanoparticles

Luis Augusto V. de Luna, Nahiara E. Zorgi, Ana Carolina M. de Moraes, Douglas S. da Silva, Sílvio R. Consonni, Selma Giorgio and Oswaldo L. Alves
Publicado por Nanotoxicology, 02/2019

Graphene oxide (GO) and silver nanoparticles (AgNPs) can be formed into a hybrid nanomaterial, known as GOAg nanocomposite, which presents high antibacterial activity. The successful translation of this nanomaterial into medical use depends on critical information about its toxicological profile. In keeping with a Safe-by-design approach, we evaluated the immunotoxicity of GOAg using J774 and primary murine macrophages. The interaction between GOAg and macrophages was investigated with a scanning electron microscope (SEM). High-throughput technologies were employed to evaluate cell viability, apoptosis/necrosis, mitochondrial depolarization and lipid peroxidation. The inflammogenicity of nanomaterials was predicted after quantification of the cytokines IL-1β, TNF-α and IL-10 before and after stimulation with interferon-γ (IFN-γ). The ratio between CD80 and CD206 macrophage populations were also estimated. In addition, the production of nitric oxide (NO) was investigated. SEM surveys revealed the potential of GOAg to induce frustrated phagocytosis. GOAg induced a dose-dependent mitochondrial depolarization, apoptosis and lipid peroxidation to J774 macrophages. GOAg toxicity was not modified in an inflammatory microenvironment, but its toxicity was within the range of concentrations used in bacterial inactivation. GOAg did not induce primary macrophages to significantly produce inflammatory cytokines, and previous macrophage stimulation did not enhance GOAg inflammogenicity. Additionally, the pristine nanomaterials and GOAg do not shift macrophages polarization towards M1. Sublethal concentrations of GOAg did not impair macrophages NO production. Finally, we suggest options for improvement of GOAg nanocomposite in ways that may help minimize its possible adverse outcomes to human health.

Designing hybrid materials with multifunctional interfaces for wound dressing, electrocatalysis, and chemical separation

Heveline D. M. Follman,Igor Messias, Maria N. Queiroz, Rafael A. Araujo, Adley F. Rubira and Rafael Silva
Publicado por Journal of Colloid and Interface Science, 01/2019

An infinite number of possibilities can emerge from the combination of phases in hybrid systems. Interfacing phases is a strategy to obtain a set of properties in one system that are beyond the abilities of single phases. Herein, the progress in materials science exploring hybrid systems are discussed from the point of view of three important applications: wound dressing; electrocatalysis; and chemical separation. These three unrelated applications exemplify the broad impact of hybrid materials, which can be coherently designed to achieve outstanding performance. Many inspiring works have been published in the last few years, remodeling the edges of human knowledge on hybrid materials. However, the challenges in the coherent design seem to rely on the development of synthetic processes to achieve stronger integration among the phases in a hybrid material.

Fe3O4@SiO2 Nanoparticles Concurrently Coated with Chitosan and GdOF:Ce3+,Tb3+ Luminophore for Bioimaging: Toxicity Evaluation in the Zebrafish Model

Latif U. Khan, Gabriela H. da Silva, Aline M. Z. de Medeiros, Zahid U. Khan, Magnus Gidlund, Hermi F. Brito, Oscar Moscoso-Londoño, Diego Muraca, Marcelo Knobel, Carlos A. Pérez and Diego Stéfani T. Martinez
Publicado por ACS Applied Nano Materials, 05/2019

In this work, design and physiochemical characterization of a biocompatible nanoplatform with integrated photoluminescence and magnetic properties were reported. The potential in vivo toxicity was assessed by exploring the biodistribution of nanoparticles using synchrotron X-ray fluorescence (SXRF) imaging in the zebrafish embryos as a biological model. Their synthesis is accessible through combining magnetic iron oxide nanoparticles with Ce3+- and Tb3+-doped GdOF luminophore and concurrent capping in situ with chitosan biopolymer. The Fe3O4@SiO2/GdOF:xCe3+,yTb3+ nanoparticles manifested near superparamagnetic behavior at 300 K, displaying green emission lines, arising from the characteristic 5D47FJ transitions (J = 6–0) of Tb3+ ion. The limited permeability of the chorion membrane is a critical factor in toxicity screening, a potential approach to remove the chorion and expose the chorion-off zebrafish embryos to nanoscale materials. Accordingly, multifunctional nanoparticles exhibited no acute toxicity to the with-chorion and chorion-off zebrafish embryos up to 100 mg L–1 exposure concentration, suggesting remarkable in vivo biocompatibility. By assessing the nanobio interaction via deep-tissue SXRF imaging, it was visualized that the distribution of Gd and Fe elements had occurred with a roughly constant relative ratio in the whole body of early-stage embryos. However, the elements mapping data revealed a predominant localization of Gd and Fe in the gastrointestinal tract, manifesting bioaccumulation of magneto-luminescent nanoparticles as an integrated nanoplatform in the respective region. This result demonstrated that the particles’ uptake by embryos were mostly through oral exposure rather than the dermal pathway, offering a new route to oral administration of nanoparticles for future biological and environmental applications.

Interaction of graphene oxide with cell culture medium: Evaluating the fetal bovine serum protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions

Lidiane S. Franqui, Marcelo A. de Farias, Rodrigo V. Portugal, Carlos A. R. Costa, Romenia R. Domingues, Antonio G. Souza Filho, Vitor R. Coluci, Adriana F. P. Leme and Diego Stéfani T. Martinez
Publicado por Materials Science and Engineering: C, 07/2019

The interaction of single-layer graphene oxide (SLGO) and multi-layered graphene oxide (MLGO) with a cell culture medium (i.e. DMEM) was studied by evaluating fetal bovine serum (FBS) protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions. SLGO and MLGO exhibited different colloidal behavior in the culture medium, which was visualized by cryogenic transmission electron microscopy in situ analysis. Exploring proteomics and bioinformatics tools, 394 and 290 proteins were identified on the SLGO and MLGO hard corona compositions, respectively. From this amount, 115 proteins were exclusively detected on the SLGO and merely 11 on MLGO. SLGO enriched FBS proteins involved in metabolic processes and signal transduction, while MLGO enriched proteins involved in cellular development/structure, and lipid transport/metabolic processes. Such a distinct corona profile is due to differences on surface chemistry, aggregation behavior and the surface area of GO materials. Hydrophilic interactions were found to play a greater role in protein adsorption by MLGO than SLGO. Our results point out implications for in vitro studies of graphene oxide materials concerning the effective dose delivered to cells and corona bioactivity. Finally, we demonstrated the importance of integrating conventional and modern techniques thoroughly to understand the GO-FBS complexes towards more precise, reliable and advanced in vitro nanotoxicity assessment.

Characterization of novel thermoresponsive poly(butylene adipate-co-terephthalate)/poly(N-isopropylacrylamide) electrospun fibers

Breno A. T. T. da Silva, Liege A. Pascoalino, Ricardo L. de Souza, Edvani C. Muniz and Priscila S. Curti
Publicado por Polymer Bulletin, 04/2019

In this work, electrospun fibers of poly(butylene adipate-co-terephthalate) (PBAT) and poly(N-isopropylacrylamide) (PNIPAAm) blends, PBAT/PNIPAAm, with different mass ratios, were obtained. For characterization of their morphological, structural, thermal and wettability properties, scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetry (TG), differential scanning calorimetry (DSC) and drop water contact angle (DWCA) measurements were carried out. The optimum conditions determined for electrospinning were: voltage of 25 kV, flow rate of 1.3 mL·h−1 and working distance of 15 cm. The most important result was achieving PBAT/PNIPAAm electrospun fibers with a thermoresponsive behavior and a sudden response to temperature at PNIPAAm’s LCST (lower critical solution temperature). From SEM analysis, the higher the content of PNIPAAm in the blend, the higher the average diameter of the electrospun fibers was; also, the higher content of PNIPAAm in the blend allowed the fibers to be rounded with no presence of beads. From ATR-FTIR analysis, no formation of strong intermolecular interactions, such as hydrogen bonding, between the PBAT and PNIPAAm chains was observed. From TG and DSC analyses, the thermal stability of the PBAT/PNIPAAm fibers remained unchanged in respect to the electrospinning. DWCA measurements for PBAT/PNIPAAm 70/30 and 50/50 fibers, in response to temperature, indicated a gap of 50° to 60° at PNIPAAm’s LCST, evidencing their high thermosensitivity. With these results, PBAT/PNIPAAm electrospun fibers with 30% or more in mass ratio of PNIPAAm might find a potential application for the cell adhesion/detachment field.

In situ growth of manganese oxide nanosheets over titanium dioxide nanofibers and their performance as active material for supercapacitor

Elisangela P. da Silva, Adley F. Rubira, Odair P. Ferreira, Rafael Silva and Edvani C. Muniz
Publicado por Journal of Colloid and Interface Science, 11/2019

In recent years, electrochemical energy devices, i.e. batteries, fuel cells, solar cells, and supercapacitors, have attracted considerable attention of scientific community. The architecture of active materials plays a crucial role for improving supercapacitors performance. Herein, titanium dioxide (TiO2) nanofibers (1D) have been synthesized by electrospinning process and used as a backbone to manganese dioxide (MnO2) nanosheets (2D) growth through hydrothermal method. This strategy allows the obtaining of 1D/2D heterostructure architecture, which has demonstrated superior electrochemical performance in relation to pristine MnO2. The highest electrochemical performance is due to the synergic effect between the metal oxides, where TiO2 nanofibers provide electrochemical stability for active MnO2 phase. Thus, the designed TiO2@MnO2 structure can reach maximum specific capacitance of 525 F·g−1 at a current density of 0.25 A·g−1, and it demonstrates an excellent stability by retaining 81% of the initial capacitance with coulombic efficiency of 91%. Therefore, the novel architecture of TiO2@MnO2 based on nanofibers and nanosheets exhibits superior electrochemical properties to be used in supercapacitor applications.

Influence of process variables on the yield and diameter of zein-poly(N‑isopropylacrylamide) fiber blends obtained by electrospinning

Ana Clara B. Vicente, Gabriela B. Medeiros, Délia do Carmo Vieira, Francielle P. Garcia, Celso V. Nakamura, Edvani C. Muniz and Elisângela Corradini
Publicado por Journal of Molecular Liquids, 10/2019

In this study, zein-poly(N‑isopropylacrylamide) fiber blends (PNIPAAm) were obtained by electrospinning. The effects of solution concentration and process parameters were evaluated by means of factorial design. The concentration proved to have a stronger effect on fiber diameter than the flow rate, although a positive interaction was identified between the factors of concentration and flow rate. Fibers with smaller diameters can be obtained at lower concentration within the electrospinnable window. The simultaneous increase in flow rate and concentration increases the fiber diameter. Concentration and flow rate have similar effects on the yield response. Higher yields can be obtained using higher concentrations and higher flow rate rates. FTIR confirmed the presence of zein and PNIPAAm in the fibers and indicated some interaction between the two polymers. The fibers showed behavior hydrophilic below 33 °C and hydrophobic from 38 °C. The mean diameter of the fibers increased with increasing solution viscosity due to the greater entanglement of the polymer chains. VERO cell viability tests made at 37 °C showed at least >90%, viability which means that the samples did not inhibit cell growth after 72 h of incubation, demonstrating good biocompatibility.

Optical, morphological and dielectric characterization of MBBA liquid crystal-doped hydrogels

Paulo R. G. Fernandes, Keila A. da Silva, Hatsumi Mukai and Edvani C. Muniz
Publicado por Journal of Molecular Liquids, 03/2017

In this work, MBBA liquid crystal-doped hydrogels are investigated through of Scanning Electron Microscopy (SEM), Polarized Optical Microscopy (POM), Optical Transmittance (OT) and Dielectric Spectroscopy (DS) techniques. For the synthesis of the hydrogels and of their composites a solution (20% water and 80% acetone) of the potassium periodate (KIO4) was prepared. The samples were prepared by radicalar photochemical polymerization of acrylamide monomer (AAm) in the presence of N, N′-methylene-bis-acrylamide (MBAAm) as a cross-linking agent. Potassium periodate (KIO4) was used as a photopolymerization initiator. In such synthesis, acrylamide monomer (AAm-Aldrich, 14, 866–5) was added with cross-linking agent MBAAm (N, N-methylene-bis-acrylamide) and liquid crystals MBBA (N-(4-methoxybenzilidene)-4(butylaniline)). The acetone was used to solubilize the liquid crystal MBBA in the solution. The resulting solution was placed and sealed between two glass plates coated with transparent and conducting films of tin oxide (SnO2) with spacer of 25 μm. All samples were investigated at 15.0 °C, 23.0 °C and 35.0 °C. The electrical behavior of the samples was characterized by using a Solartron 1260A impedance-gain phase analyzer in the frequency range from 10 mHz to 10 MHz with amplitude of 10 mV. The experimental results from DS technique are discussed by using Davidson–Cole and Havriliak–Negami approaches. As one of main results of this work we noticed that the cavities of the hydrogels synthesized with the use of acetone can be able to confine the free ions of the liquid crystal added to the polymeric matrix.

Hybrid Materials and Nanocomposites as Multifunctional Biomaterials

Heveline D. M. Follmann, Alliny F. Naves, Rafael A. Araujo, Viktor Dubovoy, Xiaoxi Huang, Tewodros Asefa, Rafael Silva and Osvaldo N. Oliveira
Publicado por Current Pharmaceutical Design, 03/2017

This review article provides an overview of hybrid and nanocomposite materials used as biomaterials in nanomedicine, focusing on applications in controlled drug delivery, tissue engineering, biosensors and theranostic systems. Special emphasis is placed on the importance of tuning the properties of nanocomposites, which can be achieved by choosing appropriate synthetic methods and seeking synergy among different types of materials, particularly exploiting their nanoscale nature. The challenges in fabrication for the nanocomposites are highlighted by classifying them as those comprising solely inorganic phases (inorganic/inorganic hybrids), organic phases (organic/organic hybrids) and both types of phases (organic/inorganic hybrids). A variety of examples are given for applications from the recent literature, from which one may infer that significant developments for effective use of hybrid materials require a delicate balance among structure, biocompatibility, and stability.

Chemical Recycling of Poly(ethylene terephthalate) (PET) by Alkaline Hydrolysis and Catalyzed Glycolysis

Tânia Marina P. Zanela, Edvani C. Muniz and Carlos Alberto P. Almeida
Publicado por Orbital: The Electronic Journal of Chemistry, 05/2018

The poly(ethylene terephthalate) (PET) is a thermoplastic polyester, non-degradable in the environment with high resistance to chemical and physical agents. Due to the substantial amount of waste generated and accumulated in the environment, chemical recycling of post-consumer PET has been considered the most successful method for polymer recycling. This work presents results of chemical recycling of post-consumer PET via alkaline hydrolysis and glycolysis. The alkaline hydrolysis is considered the most suitable to the green chemistry and this method can be carried out using mild reaction conditions. The process results in a good yield (97%) to terephthalic acid (TPA). The catalyzed glycolysis of post-consumer PET was carried out in a short reaction time and relatively low temperature, with bis (2-hydroxyethyl) terephthalate (BHET) yield of 75%. TPA and BHET were characterized by FTIR and 1H NMR techniques. The analyses proved to be successful in obtaining both products. Therefore, this work contributes to the chemical recycling studies of PET waste and encourages further studies along this research area.

Formulation of chloroaluminum phthalocyanine incorporated into PS-b-PAA diblock copolymer nanomicelles

Bruno H. Vilsinski, Maria A. Witt, Patrícia M. Barbosa, Maiara C. Montanha, Cátia S. Nunes, Ismael C. Bellettini, Lidiane V. de Castro, Francielle Sato, Mauro L. Baesso, Edvani C. Muniz and Wilker Caetano
Publicado por Journal of Molecular Liquids, 12/2018

Chloroaluminum phthalocyanine (ClAlPc) is considered to be an important photosensitizer compound, and it has been extensively explored in photodynamic therapy (PDT) against several types of cancer cell lines. However, ClAlPc is known to be a highly hydrophobic compound. Thus, it requires physical association with a drug delivery system for clinical use. In this study, distinct formulations of PS70.5-b-PAA13 diblock copolymer nanostructures containing ClAlPc were studied. Results found in this study showed that the ClAlPc/PS70.5-b-PAA13 diblock composite presented micellar morphology and a size of 200 nm while dispersed in aqueous media. Additionally, zeta potential studies revealed that such formulations presented colloidal stability with low polydispersity index (PDI) values (0.121). The encapsulation efficiency of ClAlPc by such copolymer micelles, made through spectroscopic measures, was higher than 95% while at the phthalocyanine concentration range from 9.0 to 70 μmol L−1. Spectroscopic studies also showed that the existence of monomeric ClAlPc in such nanostructured micelles is closely dependent on the PS concentration. Low PS concentration resulted in monomeric ClAlPc, as observed from the correspondent absorption and emission spectra of freshly-prepared composite. However, even after 15 days of storage and at low PS concentration, the ClAlPc can self-aggregate within the polymer-micellar nanoenvironment (as observed through spectroscopic studies). Photophysical properties of ClAlPc incorporated in the PS-b-PAA copolymer system revealed promising values of oxygen singlet generation (ΦΔ1O2 = 0.3). Skin permeation studies performed by photoacoustic spectroscopy showed that the ClAlPc/PS-b-PAA nanosystem permeates and reaches the superficial dermis layer. In vitro tests, using Caco-2 cell-lines incubated with ClAlPc/PS-b-PAA formulations at different phthalocyanine concentrations, showed cellular damage after 30 min under light radiation (663 nm with LED, fluence of 1.62 μJ cm−2). The IC50 obtained for the system containing ClAlPc/PS-b-PAA was 1.74 · 10−7 mol L−1. Furthermore, no cytotoxicity effect was observed during cell growth tests performed using both ClAlPc/PS-b-PAA composite and pristine PS-b-PAA nanomicelles in the absence of light irradiation. These findings suggested that the PS-b-PAA diblock copolymer produced a promising nanostructured system suitable for the incorporation of the hydrophobic ClAlPc photosensitizer and for subsequent use in the PDT field.

Magnetic microspheres composite from poly(ethylene terephthalate) (PET) waste: Synthesis and characterization

M. F. Viante, T. M. P. Zanela, A. Stoski, E. C. Muniz and C. A. P. Almeida
Publicado por Journal of Cleaner Production, 10/2018

In this study, a novel composite of magnetic microspheres was prepared using the bis-(2-hydroxyethyl) terephthalate (BHET) monomer obtained from the catalyzed glycolysis of post-consumer poly(ethylene terephthalate) (PET). BHET, the main product obtained from a complete PET glycolysis, was modified with glycidyl methacrylate (GMA) at 60 °C in dimethylsulphoxide (DMSO) and catalyzed by N,N,N′,N′-tetramethylethylenediamine (TEMED). The magnetic composite was obtained through the synthesis of polymeric matrix and magnetite nanoparticles (Fe3O4@AO) via chemical co-precipitation. The samples were characterized by HPLC-UV, 1H NMR, 13C NMR, dynamic light scattering (DLS), X-ray diffraction (XRD), magnetization (VSM), and scanning electronic microscopy (SEM). The analysis showed the predominant insertion of vinyl groups, derived from GMA in the BHET structure, via opening the epoxide ring. The magnetic microspheres presented pores and iron uniformly distributed on their surfaces. The novel composite can have promising applications such as in the removal of pollutants from the environment.

Biomimetic nanocomposite based on hydroxyapatite mineralization over chemically modified cellulose nanowhiskers: An active platform for osteoblast proliferation

Elizângela H. Fragal, Thelma S. P. Cellet, Vanessa H. Fragal, Maria A. Witt, Mychelle V. P. Companhoni, Tânia Ueda-Nakamura, Rafael Silva and Adley F. Rubira
Publicado por International Journal of Biological Macromolecules, 03/2019

Functionalized-cellulose nanowhiskers (CNWs) were obtained and used to improve hydroxyapatite (HAp) growth by the biomimetic method. CNWs were obtained through HCl hydrolysis and then submitted to chemical functionalization with carboxylate or amine groups that can induce selective HAp mineralization efficiently. Functionalized-CNWs were tested against HAp growth through the biomimetic method using a simulated body fluid (SBF) as a medium during 14 and 28 days of mineralization. Both chemical surface nature (bearing carboxylate or amine reactive groups) and contact time with SBF influenced the nucleation and growth of HAp crystals over CNWs surface. Nanocomposites immersed for 28 days showed a higher amount of HAp crystals compared to bare CNWs or the ones immersed for 14 days. Biocompatibility of the nanomaterials immersed for 14 days in SBF was evaluated through cell viability test using pre-osteoblasts (MC3T3-E1). In general, functionalized-CNWs containing HAp crystals deposited through biomimetic method showed promising results, with CNWs bearing amine groups showing a slightly larger biocompatibility compared to the ones bearing carboxylate groups during an incubation period of 24 h.

Effect of phase composition on the photocatalytic activity of titanium dioxide obtained from supercritical antisolvent

Elisangela P. da Silva, Manuel E. G. Winkler, Willyan M. Giufrida, Lucio Cardozo-Filho, Christian G. Alonso, Jardel B. O. Lopes, Adley F. Rubira and Rafael Silva
Publicado por Journal of Colloid and Interface Science, 02/2019

Photocatalytic activity of TiO2 nanoparticles is highly dependent on their phase composition. The coexistence of anatase and rutile phases in a single nanoparticle eases the electron transfer process between the phases, and favors the separation of photogenerated pairs. In this work, highly photoactive mixed-phase TiO2 nanostructures were prepared by supercritical antisolvent precipitation (SAS), an environmentally friendly technology. It is shown here that this methodology has the remarkable ability to produce highly porous (515 m2/g) and crystalline TiO2 nanoparticles. The phase composition of as-prepared TiO2 samples can be tailored through annealing process. Several mixed-phase TiO2 samples were tested to assess the correlation between photocatalytic activity and phase composition. The photocatalytic performance is strongly affected by the anatase-rutile ratio, since the synergism between phases enhances the charge separation, reducing the recombination effect of the photogenerated pairs (e/h+). It was found that the nanocatalyst composed by 7.0 wt% of rutile phase and 93.0 wt% of anatase phase, named as TiO2_650, presented the highest photodegradation for both methyl orange (MO) and methylene blue (MB) dyes. Interestingly, TiO2 samples prepared by SAS have superior photoactivity than the benchmark photocatalyst names as P25, which is a widely used TiO2 material composed of anatase and rutile phases.

Nanoporous Heteroatom-Doped Carbons Derived from Cotton Waste: Efficient Hydrazine Oxidation Electrocatalysts

Taís L. Silva, André L. Cazetta, Tao Zhang, Katherine Koh, Rafael Silva, Tewodros Asefa and Vitor C. Almeida
Publicado por ACS Applied Energy Materials, 02/2019

In this work, cotton-based denim waste is successfully used as a precursor to synthesize nanoporous P- and N-co-doped carbon materials that can serve as efficient electrocatalysts for the hydrazine oxidation reaction (HzOR). In the synthesis, the cotton denim waste is mixed with H3PO4 in two different denim/H3PO4 (wt/vol) ratios, namely, 1:1 and 1:3, wherein H3PO4 serves as both an activating agent and a source of P dopant atoms while the indigo carmine dye present in denim serves as a source of N dopant atoms to the carbon materials. The resulting P- and N-co-doped carbon materials, named PNC1 and PNC3, respectively, are characterized by various analytical techniques. The XPS spectra show that PNC1 has ca. 2.17 atomic % P and 1.95 atomic % N whereas PNC3 has 2.54 atomic % P and 0.71 atomic % N. Pore analyses by N2 porosimetry indicate that PNC1 has a higher surface area (1582 m2 g–1) than PNC3 (486 m2 g–1), although the former has a lower mesopore volume (0.39 cm3 g–1) than the latter (0.58 cm3 g–1). The SEM images of the two materials also show some notable structural differences. The results overall indicate that the structures and compositions of the materials can be easily tailored by varying the ratio of denim/H3PO4 in the precursor. The electrocatalytic activities of PNC1 and PNC3 toward HzOR were then evaluated, and PNC3 is found to be a better electrocatalyst than PNC1. In a 100 mmol L–1 hydrazine solution in phosphate buffer saline (PBS) at pH 7.4, PNC3 electrocatalyzes the reaction at a lower peak potential (ca. 0.70 V vs RHE) than PNC1 (ca. 0.77 V vs RHE). Additionally, the current density obtained during HzOR over PNC3 is higher (by 1.29 times) than the one obtained over PNC1. Furthermore, the onset potential by which PNC3 electrocatalyzes HzOR (0.42 V vs RHE) is comparable to or better than the values reported for some of the best HzOR electrocatalysts in the literature. Besides their high electrocatalytic activity, the materials remain stable during electrocatalysis of HzOR.

Synthesis and characterization of pecan nutshell-based adsorbent with high specific area and high methylene blue adsorption capacity

Hugo H. C. Lima, Rogério S. Maniezzo, Maria E. G. Llop, Vincente L. Kupfer, Pedro A. Arroyo, Marcos R. Guilherme, Adley F. Rubira, Emerson M. Girotto, Andrelson W. Rinaldi
Publicado por Journal of Molecular Liquids, 02/2019

In this work, a pecan nutshell was used as a precursor to prepare activated hydrochar (HPN-ATV) with a high specific area. HPN-ATV was engineered as an adsorbent for the removal of methylene blue (MB) from aqueous environments. The obtained materials were characterized using textural, morphological, and chemical analysis techniques. HPN-ATV showed a BET specific area of 2342 m2 g−1 and an average pore diameter of 2.24 nm. Boehm titration and FTIR spectral analysis indicated the presence of acidic and basic functional groups on the surface of HPN-ATV, which rendered the removal of cationic molecules more favorable. The kinetic experimental data better correlated with the pseudo-second-order kinetic and Elovich equations, and the Langmuir model showed a better fit for the data of MB adsorption. The adjusting parameters indicated a monolayer with an adsorption capacity of 1190.62 mg g−1, which is higher than that of the other adsorbents reported in literature. In addition, the thermodynamic data suggested a spontaneous adsorption process with endothermic characteristics.

Ultra-absorbent hybrid hydrogel based on alginate and SiO2 microspheres: A high-water-content system for removal of methylene blue

Caroline O. Panão, Eduardo L. S. Campos, Hugo H. C. Lima, Andrelson W. Rinaldi, Michele K. Lima-Tenório, Ernandes T. Tenório-Neto, Marcos R. Guilherme, Tewodros Asefa and Adley F. Rubira
Publicado por Journal of Molecular Liquids, 02/2019

This work reports the synthesis of hybrid hydrogels based on alginate and π-bonds coupled silica (SiO2) microspheres (~250 nm) with high performance for water absorption. For formation of the hybrid hydrogel, the alginate was covalently gelled in the presence of SiO2 vinylated with vinyltrimethoxysilane using crosslinking chemistry. These hydrogels can absorb until 889.76 ± (12.65) g of water per 1 g of dry polymer without their tridimensional shape being unmade. The chemical nature of the polymer and the surface charges of the microspheres play a major role in creating the highly hydrophilic structure and determining the superabsorption properties. The porosity of the matrix also contributes to increase the effectiveness of the absorption, owing to an interconnected pore network that allows absorbed water to be distributed throughout the polymer matrix. In the buffer solutions, the hydrogels showed lower capacity for absorption, which was attributed to ions from weak acids and their respective salts changing charge distribution between the polymer network and the surrounding liquid layer. The applicability of the hydrogel for removal of methylene blue (MB) was investigated. The removal of MB increases with an increase in the amount of modified alginate and monomers, but reduces with a decrease in the amount of vinylated SiO2. The experimental data were better correlated with pseudo-second order model and the Langmuir model was better fit for the equilibrium data, indicating that MB was absorbed predominantly via chemisorption owing to electrostatic interactions of the dye molecule with a single absorption site.

Two-dimensional thermoresponsive sub-microporous substrate for accelerated cell tissue growth and facile detachment

Vanessa H. Fragal, Daniele M. Catori, Elizângela H. Fragal, Francielle P. Garcia, Celso V. Nakamura, Adley F. Rubira and Rafael Silva
Publicado por Journal of Colloid and Interface Science, 07/2019

Thermoresponsive sub-microporous films having a lower critical solution temperature (LCST), promptly obtained by using the breath figure method, were applied to tissue engineering. These sub-microporous films, sized 100–400 nm, were prepared by blending poly(N-isopropylacrylamide) (PNIPAAm) with polystyrene (PS), in addition to applying the dynamic breath figure (BF) method. The thermoresponsive blends were prepared with polyethylene terephthalate (PET) substrate by using a spin coater; the pore size was modulated according to the spin speed. The sub-microporous films, either with pure PNIPAAm or with different PNIPAAm contents were applied as substrates in order to obtain cell growth (Vero cells); moreover, the effect of PNIPAAm use was evaluated. The PNIPAAm sub-microporous films made the cellular viability to be 9-13-fold higher than the control sample commonly used in cell culture. In addition, the thermoresponsive PNIPAAm properties were even noticed at a low PNIPAAm content in the porous films. Such polymer system was successfully applied to detach the Vero cell tissue using temperature variation.

Effects of a strong π-accepting ancillary ligand on the water oxidation activity of weakly coupled binuclear ruthenium catalysts

Tiago A. Matias, Francisca N. Rein, Reginaldo C. Rocha, André Luiz B. Formiga, Henrique E. Toma and Koiti Araki
Publicado por Dalton Transactions, 02/2019

Significant differences were found in the proton-coupled redox chemistry and catalytic behavior of the binuclear [{Ru(H2O)(bpz)}2(tpy2ph)](PF6)4 complex [bpz = 2,2′-bipyrazine; tpy2ph = 1,3-bis(4′-2,2′:6′,2′′-terpyridin-4-yl)benzene] as compared with the structurally analogous derivative with 2,2′-bipyridine (bpy) instead of bpz. The differences were assigned to the stronger π-accepting character of bpz relative to bpy as the ancillary ligand. The expectation of a positive shift for the Ru-centered redox potentials was confirmed for the lower oxidation state species, but that trend was reversed in the formation of the high-valence catalytic active species as shown by a negative shift of 0.14 V for the potential of the [RuIV/V=O] process. Moreover, DFT calculations indicated a significant decrease of about 15% on the spin density and oxyl character of the [RuV=O]3+ fragment. The significantly lower kcat(O2) for the bpz system was attributed to these combined electronic effects.

Enhanced performance of 3D printed graphene electrodes after electrochemical pre-treatment: Role of exposed graphene sheets

Pãmyla L. dos Santos, Vera Katic, Hugo C. Loureiro, Matheus F. dos Santos, Diego P. dos Santos, André L. B. Formiga and Juliano A. Bonacin
Publicado por Sensors and Actuators B: Chemical, 02/2019

3D printing has been reported as a remarkable technology for development of electrochemical devices, due to no design constraints, waste minimization and, most importantly, fast prototyping. The use of 3D printed electrodes for electroanalytical applications is still a challenge and demand efforts. In this work, we have developed low-cost and reproducible 3D-printed graphene electrodes for electrocatalytic detection of dopamine. Electrocatalytic features were enhanced after electrochemical pre-treatment. The oxidation and reduction at different potential ranges, in 0.1 mol L−1 phosphate buffer solution (pH = 7.4), are used to modulate the structural and morphological characteristics of the electrodes. Since, the electrochemical properties of the electrodes, including electron transfer kinetic and the electrocatalytic activity, are strongly influenced by electronic properties and the presence of functional groups. Raman spectroscopy, SEM and AFM microscopes and electrochemical techniques were used to characterize the 3D electrodes before and after the electrochemical pre-treatments. Finally, the performances of the 3D-printed graphene electrodes were evaluated towards dopamine sensing. The best performance was achieved by oxidation at + 1.8 V vs. SCE for 900 s and reduction from 0.0 V to -1.8 V vs. SCE at 50 mV s−1. The proposed sensor presented linear response from 2.0 μmol L−1 to 10.0 μmol L−1, with detection limit of 0.24 μmol L−1.

Crystal structure, electrochemical and spectroscopic investigation of mer-tris­[2-(1H-imidazol-2-yl-κN3)pyrimidine-κN 1]ruthenium(II) bis­(hexa­fluorido­phosphate) trihydrate

Naheed Bibi, Renan B. Guerra, Luis Enrique S. C. Huamaní and André Luiz B. Formiga
Publicado por Acta Crystallographica Section E: Crystallographic Communications, 07/2018

The crystal structure of the title compound, [Ru(C7H6N4)3](PF6)2.3H2O, a novel RuII complex with the bidentate ligand 2-(1H-imidazol-2-yl)pyrimidine, comprises a complex cation in the meridional form exclusively, with a distorted octa­hedral geometry about the ruthenium(II) cation. The Ru—N bonds involving imidazole N atoms are comparatively shorter than the Ru—N bonds from pyrimidine because of the stronger basicity of the imidazole moiety. The three-dimensional hydrogen-bonded network involves all species in the lattice with water mol­ecules inter­acting with both counter-ions and NH hydrogen atoms from the complex. The supra­molecular structure of the crystal also shows that two units of the complex bind strongly through a mutual N—H⋯N bond. The electronic absorption spectrum of the complex displays an asymmetric band at 421 nm, which might point to the presence of two metal-to-ligand charge-transfer (MLCT) bands. Electrochemical measurements show a quasi-reversible peak referring to the RuIII/RuII reduction at 0.87 V versus Ag/AgCl.