Navegando por Palavras-chave "Cellulose Nanocrystal"

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    Produção De Scaffolds De Poli(3-Hidroxibutirato-Co-3-Hidroxivalerato) Reforçados Com Nanocristais De Celulose Para Engenharia De Tecido
    (Universidade Federal de São Paulo (UNIFESP), 2017-12-15) Montanheiro, Thais Larissa Do Amaral [UNIFESP]; Lemes, Ana Paula [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    This work had as objective the production and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose nanocrystals (CNC) scaffolds, by thermally induced phase separation (TIPS), for application in the area of tissue engineering. The effect of two modifications on CNC’s surface on the final properties of the scaffolds was evaluated, one of them being acetylation of CNC (CNC-Ac) and the other, the adsorption of polyethylene glycol (CNC-PEG). Both modifications were characterized and confirmed by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential and thermogravimetry (TGA). TEM images showed the presence of agglomerates for CNC-Ac and CNC-PEG, confirming the reduction of hydrophilicity. On FTIR were observed new bands confirming the acetylation reaction, but the adsorption of PEG could not be confirmed by FTIR. The crystallinity index, obtained by XRD, was reduced about 12% after acetylation, and 18% after pegylation. Zeta potential of both samples was also changed, in both cases to more positive values. The thermal stability was reduced after both functionalizations, being more affected after the adsorption of PEG. The scaffolds were produced with 6% w/v PHBV/dioxane and using quenching temperature of -43 ± 2 °C. PHBV, PHBV/CNC, PHBV/CNC-Ac and PHBV/CNC-PEG scaffolds were then produced with concentrations of 1, 2 and 3 wt% of CNC, CNC-Ac and CNC-PEG. Morphological analysis showed that the scaffolds presented porous structure and interconnected pores. The introduction of CNC, CNC-Ac and CNC-PEG caused reduction in porosity values due to the changes in the solution behavior during phase separation. It was also detected that the nanoparticles could not be well dispersed in the samples. The addition of CNC, CNC-Ac and CNC-PEG caused, in general, a slight increase in the crystallinity degree the scaffolds. In the uniaxial compression tests were obtained values compatible for application as human articular cartilage, spinal disc, trabecular bone and skin. Gas chromatography analysis showed that there is no residual solvent in the scaffolds, and this result was confirmed by the cell viability assays, which showed lack of cytotoxicity in the samples, and stimulated cell proliferation/activity, with cell viability values above 84%.