ARTIGOS

COVALENT FUNCTIONALIZATION OF GRAPHENE OXIDE WITH D-MANNOSE: EVALUATING THE HEMOLYTIC EFFECT AND PROTEIN CORONA FORMATION

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.

DOI:10.1039/C7TB02997G

FOLIC ACID-FUNCTIONALIZED GRAPHENE OXIDE NANOCARRIER: SYNTHETIC APPROACHES, CHARACTERIZATION, DRUG DELIVERY STUDY AND ANTI-TUMOR SCREENING

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

NANO SILVER VANADATE AGVO3: SYNTHESIS, NEW FUNCTIONALITIES AND APPLICATIONS

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

NANOCOMPOSITES BASED ON GRAPHENE OXIDE AND MESOPOROUS SILICA NANOPARTICLES: PREPARATION, CHARACTERIZATION AND NANOBIOINTERACTIONS WITH RED BLOOD CELLS AND HUMAN PLASMA PROTEINS

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.

PRESSURE-INDUCED PHASE TRANSITION AND FRACTURE IN ALPHA-MOO3 NANORIBBONS

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.

COATING CARBON NANOTUBES WITH HUMIC ACID USING AN ECO-FRIENDLY MECHANOCHEMICAL METHOD: APPLICATION FOR CU(II) IONS REMOVAL FROM WATER AND AQUATIC ECOTOXICITY

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.

ANTIMICROBIAL TEXTILES: BIOGENIC SILVER NANOPARTICLES AGAINST CANDIDA AND XANTHOMONAS

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.

CELLULOSE ACETATE MEMBRANE EMBEDDED WITH GRAPHENE OXIDE-SILVER NANOCOMPOSITE AND ITS ABILITY TO SUPPRESS MICROBIAL PROLIFERATION

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

ELEMENTAL ION RELEASE AND CYTOTOXICITY OF ANTIMICROBIAL ACRYLIC RESINS INCORPORATED WITH NANOMATERIAL

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

OBJECTIVES:
This study evaluated the release of ions and the cytotoxicity of acrylic resins incorporated with silver vanadate decorated with silver nanoparticles (AgVO3).
BACKGROUND:
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.
MATERIALS AND METHODS:
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).
RESULTS:
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.
CONCLUSIONS:
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

SUPRAMOLECULAR APPROACH TO DECORATE MULTI-WALLED CARBON NANOTUBES WITH NEGATIVELY CHARGED IRON(II) COMPLEXES

Sergio A. V. Jannuzzi, Bianca Martins, Luis E. S. C. Huamaní & André L. B. Formiga
Publicado por Journal of the Brazilian Chemical Society, 05/2016

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.

SYNTHESIS, CHARACTERIZATION AND PRELIMINARY ANTIMICROBIAL ASSAYS OF COPPER(II) COMPLEXES WITH 2-(IMIDAZOLE-2-YL)HETEROARYL LIGANDS

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.

EXTENDED Π-SYSTEM AND ENHANCED ELECTRONIC DELOCALIZATION ON SYMMETRIC [Ru3O(CH3COO)6(L)3]N COMPLEXES COMBINED TO AZANAPHTHALENE LIGANDS

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.

SYNTHESIS, STRUCTURAL AND MAGNETIC CHARACTERIZATION OF A COPPER(II) COMPLEX OF 2,6-DI(1H-IMIDAZOL-2-YL)PYRIDINE AND ITS APPLICATION IN COPPER-MEDIATED POLYMERIZATION CATALYSIS.

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.

Pt(II) AND Pd(II) COMPLEXES WITH IBUPROFEN HYDRAZIDE: CHARACTERIZATION, THEORETICAL CALCULATIONS, ANTIBACTERIAL AND ANTITUMOR ASSAYS AND STUDIES OF INTERACTION WITH CT-DNA

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.

CRYSTAL STRUCTURE, ELECTROCHEMICAL AND SPECTROSCOPIC INVESTIGATION OF MER-TRIS[2-(1H-IMIDAZOL-2-YL-κN3)PYRIMIDINE-κN1]RUTHENIUM(II) BIS(HEXAFLUORIDOPHOSPHATE) TRIHYDRATE.

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.

FATIGUE FAILURE LOAD OF AN ADHESIVELY-CEMENTED LITHIUM DISILICATE GLASS-CERAMIC: CONVENTIONAL CERAMIC ETCHING VS ETCH & PRIME ONE-STEP PRIMER.

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

Objectives

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.

Methods

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.

Results

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.

Significance

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.

ELECTRICITY ON RUBBER SURFACES: A NEW ENERGY CONVERSION EFFECT

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.

GRAPHITE EXFOLIATION IN CELLULOSE SOLUTIONS

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.

WHERE IS WATER IN THE TRIBOELECTRIC SERIES?

Thiago Augusto Lima Burgo, Fernando Galembeck & Gerald H. Pollack
Publicado por Journal of Electrostatics, 04/2016

Water flowing through tubes of different materials and collected in a Faraday cup contains net electric charge. Water charge is always positive but its magnitude depends on the material position in most triboelectric series. On the other hand, water acquires net negative electric charge when falling through air but its charge is modified after it passes through an electric field. Thus, water is located on the top of the triboelectric series and its charge is a robust and reliable way to organize materials within the triboelectric series, giving due attention to its surface properties.

ELECTRIFIED WATER: LIQUID, VAPOR AND AEROSOL

Thiago Augusto Lima Burgo & Fernando Galembeck
Publicado por Journal of the Brazilian Chemical Society, 09/2015

Many reports associate electrostatic charge in dielectrics with water, either bulk, finely dispersed in aerosol or as atmospheric vapor. Two widespread but currently controversial assumptions relevant to this topic are the prevalence of electroneutrality and the passive role of water in electrical phenomena, dissipating charge due to its significant electrical conductivity. Early reports from Faraday, Kelvin and their contemporaries also point towards an active role of water as an electrifying agent. Unfortunately, these have been largely ignored or treated as scattered pieces of scientific curiosity, for over a century. New trends in this area have been developing since the late 1990s, due to a number of findings leading to radically new ideas. These derive from the experimental demonstration of widespread occurrence of non-electroneutral water and from charge partition associated with a number of interfacial phenomena, even in electrically shielded environments within grounded enclosures. This is an account on the formation and persistence of electrified water in various natural or anthropic environments, followed by experimental results obtained under well-defined conditions that are revealing different mechanisms for the role of water in charge acquisition and dissipation in dielectrics.

ON THE SPONTANEOUS ELECTRIC-BIPOLAR NATURE OF AEROSOLS FORMED BY MECHANICAL DISRUPTION OF LIQUIDS

Thiago Augusto Lima Burgo & Fernando Galembeck
Publicado por Colloids and Interface Science Communications, 07/2015

Aqueous aerosols are widely found on the Earth's atmosphere and they participate from any anthropic environment. We show here that aerosols produced by a nebulizer based on splashing contain both positive and negative droplets, this means, it is bipolar but the overall aerosol charge is usually non-zero. Charge distribution within the aerosol is by itself fractal, as previously observed in other cases of mechano-chemical charge formation that is an important mechanism for producing triboelectricity in solids. The present information added to the other authors' work leads to a particle charging mechanism based on charge partition at interfaces combined to the variability of interfacial area/volume ratio in aqueous droplets, thus explaining the formation of bipolar aerosol. The demonstration of charge bipolar distribution within aerosols contributes to explain the ubiquity of electric charge patterns in solid surfaces that is receiving growing evidence and contributes to understand both beneficial and damaging outcomes of electrostatic charging.

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.

NANOPHARMACEUTICALS AND THEIR APPLICATIONS IN BLADDER CANCER THERAPY: A MINI REVIEW

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.

BIOGENIC SYNTHESIS OF IMPORTANT ENVIRONMENTAL MINERALS: MAGNESIUM PHOSPHATE COMPOUNDS AND PERSPECTIVES

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 ParoDias, ngela C. Malheiros Luzo, Bruno B.Volpe, MarcelaDurán, Sofia E.M.Galdames, Luiz A.B.Ferreira, NelsonDuráne, 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.

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.

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.

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.

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.

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 H.de 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.

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 N/I, 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.

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 R.de 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 .

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.

CELLULOSE ACETATE MEMBRANE EMBEDDED WITH GRAPHENE OXIDE-SILVER NANOCOMPOSITES AND ITS ABILITY TO SUPPRESS MICROBIAL PROLIFERATION

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.

POLYMORPHIC TRANSFORMATION MORPHOLOGY OF ISOTACTIC POLY(1-BUTENE)/POLY(PROPYLENE-CO-1-BUTENE-CO-ETHYLENE) BLENDS

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.

AMPHIPHILIC NUCLEATING AGENTS TO ENHANCE CALCIUM PHOSPHATE GROWTH ON POLYMERIC SURFACES

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.

TAILORING SCAFFOLD POROSITY FOR TISSUE REGENERATION

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.

CELLULOSE ACETATE/CELLULOSE NANOFIBER MEMBRANES FOR WHEY AND FRUIT JUICE MICROFILTRATION

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.

SOLVENT-FREE AND BIOCOMPATIBLE MULTIPHASED ORGANIC-INORGANIC HYBRID NANOCOMPOSITES

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.