Navegando por Palavras-chave "Composite"
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- ItemSomente MetadadadosCalcium phosphate fibers coated with collagen: in vivo evaluation of the effects on bone repair(Cadernos Saude Publica, 2016) Ueno, Fabio Roberto [UNIFESP]; Kido, Hueliton Wilian [UNIFESP]; Granito, Renata Neves [UNIFESP]; Gabbai-Armelin, Paulo Roberto [UNIFESP]; Magri, Angela Maria Paiva [UNIFESP]; Fernandes, Kelly Rossetti [UNIFESP]; Silva, Antonio Carlos da; Braga, Francisco José Correa; Renno, Ana Claudia Muniz [UNIFESP]The aim of this study was to assess the characteristics of the CaP/Col composites, in powder and fiber form, via scanning electron microscopy (SEM), pH and calcium release evaluation after immersion in SBF and to evaluate the performance of these materials on the bone repair process in a tibial bone defect model. For this, four different formulations (CaP powder -CaPp, CaP powder with collagen -CaPp/Col, CaP fibers - CaPf and CaP fibers with collagen - CaPf/Col) were developed. SEM images indicated that both material forms were successfully coated with collagen and that CaPp and CaPf presented HCA precursor crystals on their surface. Although presenting different forms, FTIR analysis indicated that CaPp and CaPf maintained the characteristic peaks for this class of material. Additionally, the calcium assay study demonstrated a higher Ca uptake for CaPp compared to CaPf for up to 5 days. Furthermore, pH measurements revealed that the collagen coating prevented the acidification of the medium, leading to higher pH values for CaPp/Col and CaPf/Col. The histological analysis showed that CaPf/Col demonstrated a higher amount of newly formed bone in the region of the defect and a reduced presence of material. In summary, the results indicated that the fibrous CaP enriched with the organic part (collagen) glassy scaffold presented good degradability and bone-forming properties and also supported Runx2 and RANKL expression. These results show that the present CaP/Col fibrous composite may be used as a bone graft for inducing bone repair.
- ItemAcesso aberto (Open Access)Estudo de compósitos formados a partir de nanopartículas de fluoreto de lantânio(Universidade Federal de São Paulo, 2015-10-16) Secco, Henrique de Lima [UNIFESP]; Philadelphi, Laura Oliveira Peres [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The combination of materials to form hybrids with unique properties, different from those of the isolated components, is a strategy used to prepare functional materials with improved properties aiming to allow their application in specific fields. Lanthanum fluoride is one of the rare earth ionic compounds most extensively studied nowadays, mainly due to its high ionic conductivity, which makes it attractive for sensors applications, also due to the easy doping of its structure with other rare earth elements, because of the similarity between those elements. This strategy is commonly used to obtain luminescent particles, which may be useful to the manufacturing of electronic devices? displays and biological markers, for instance. In this work, nanoparticles of lanthanum fluoride, undoped and doped with cerium and europium, were synthesized through the co-precipitation method in aqueous solution. The dynamic light scattering analyses and the zeta potential showed that the dispersions present sizes within the nanoscale and good stability. The doping by substitution of the lanthanum by other rare earth elements resulted in smaller particle sizes; and that fact is in accordance with the smaller crystallite sizes calculated for the doped samples. Aiming the formation of solid state films, composites of nanoparticles in an elastomeric matrix, the nitrile rubber (NBR), were prepared. Luminescent films were prepared through the casting and spin coating techniques, based on LaF3 doped with europium and cerium, the films presented characteristic emissions in the violet (392 nm) and orange (592 nm) regions, respectively. The thermal analysis of the composites did not show a significant gain of stability when compared to the nitrile rubber alone. The scanning electron microscopy results indicate different sizes and dispersion of the nanoparticles in the polymeric matrix for each technique of film formation; these differences may result in different optical properties of the composites.
- ItemSomente MetadadadosGrowth of vertically aligned carbon nanotubes on carbon fiber: thermal and electrochemical treatments(Springer, 2013-07-01) Almeida, D. A. L.; Antunes, E. F. [UNIFESP]; Silva, V. Q. da; Baldan, M. R.; Ferreira, N. G.; INPE; Universidade Federal de São Paulo (UNIFESP)Composite electrodes of vertically aligned carbon nanotubes (VACNT) were synthesized on carbon fiber (CF) substrate by pyrolysis of camphor/ferrocene using a SiO2 interlayer as a barrier against metal diffusion into the substrate. Two treatments were used to remove iron from CF/VACNT structure: thermal annealing at high temperature under inert atmosphere and electrochemical oxidation in H2SO4 solution. the composites were characterized by scanning electron microscopy and Raman scattering spectroscopy. Besides, the electrochemical behavior of CF/VACNT was analyzed by cyclic voltammetry and charge/discharge tests. CF/VACNT composite submitted to the electrochemical oxidation showed the best electrochemical performance, with high specific capacitance, which makes it very attractive as electrode for supercapacitors.
- ItemSomente MetadadadosInfluence of neodymium ions on photocatalytic activity of TiO2 synthesized by sol-gel and precipitation methods(Elsevier B.V., 2011-02-14) Hewer, T. L. R.; Souza, E. C. C.; Martins, T. S. [UNIFESP]; Muccillo, E. N. S.; Freire, R. S.; Universidade de São Paulo (USP); IPEN; Universidade Federal de São Paulo (UNIFESP)Titanium dioxide with and without the addition of neodymium ions was prepared using sol-gel and precipitation methods. the resulting catalysts were characterized by thermal analysis, X-ray diffraction and BET specific surface area. Neodymium addition exerted a remarkable influence on the phase transition temperature and the surface properties of the TiO2 matrix. TiO2 samples synthesized by precipitation exhibit an exothermic event related from the amorphous to anatase phase transition at 510 degrees C, whereas in Nd-doped TiO2 this transition occurred at 527 degrees C. A similar effect was observed in samples obtained using sol-gel method. the photocatalytic reactivity of the catalysts was evaluated by photodegradation of Remazol Black B (RB) under ultraviolet irradiation. Nd-doped TiO2 showed enhanced photodegradation ability compared to undoped TiO2 samples, independent of the method of synthesis. in samples obtained by sol-gel, RB decoloration was enhanced by 16% for TiO2 doped with 0.5% neodymium ions. (C) 2010 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosInvestigations in MnAs1-xSbx: Experimental validation of a new magnetocaloric composite(Elsevier B.V., 2015-01-15) Campos, A. de; Luz, M. S. da; Campos, Adriana de; Coelho, A. A.; Cardoso, L. P.; Santos, A. O. dos; Gama, S. [UNIFESP]; UFTM; Universidade Estadual de Campinas (UNICAMP); UFMA; Universidade Federal de São Paulo (UNIFESP)An overview of the magnetocaloric properties of the MnAs1-xSbx is presented. the temperature dependence of the isothermal magnetic entropy, Delta S-mag and the refrigerant capacity, RC, have been investigated theoretically and experimentally in a composite based on second order MnAs1-xSbx phases. This work demonstrates the outstanding agreement between the experimental results and the continuous curves predicted by numerical calculations, indicating that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response in magnetic refrigerator performing an Ericsson cycle near room temperature. (C) 2014 Elsevier B.V. All rights reserved
- ItemSomente MetadadadosMagnetocaloric effect in Gd(1-y)DyyAl2(Elsevier B.V., 2014-01-01) Alho, B. P.; Ribeiro, P. O.; Alvarenga, T. S. T.; Carvalho, A. Magnus G. [UNIFESP]; Von Ranke, P. J.; Universidade do Estado do Rio de Janeiro (UERJ); Universidade Federal de São Paulo (UNIFESP); INMETROIn this work we calculate the magnetic properties and the magnetocaloric effect in Gd-1- yDyyAl2 (y = 0, 0.25, 0.5, 0.75 and 1). the model Hamiltonian includes contributions from the Zeeman effect, the crystalline electrical field anisotropy and the exchange interactions among Gd-Gd, Gd-Dy and Dy-Dy ions. To obtain a composite with Delta S-T as constant as possible in the temperature range from T = 60 K to 170 K, the appropriate concentrations of the five compounds investigated were calculated using the Smaili and Chahine method. the magnetization and Delta S-T dependences on temperature in the composite were simulated and compared with the partial contributions of the single magnetic component materials. Also, the magnetic field dependence on magnetization was investigated in Gd0.25Dy0.75Al2, where the discontinuous spin reorientation transitions were predicted for magnetic fields lower than 2 T, applied along <110> direction. (C) 2013 Elsevier Ltd and IIR. All rights reserved.
- ItemSomente MetadadadosOsteoconductive properties of two different bioactive glass forms (powder and fiber) combined with collagen(Elsevier Science Bv, 2017) Magri, Angela Maria Paiva [UNIFESP]; Fernandes, Kelly Rossetti [UNIFESP]; Ueno, Fabio Roberto [UNIFESP]; Kido, Hueliton Wilian [UNIFESP]; Silva, Antonio Carlos da; Braga, Francisco José Correa; Granito, Renata Neves [UNIFESP]; Gabbai-Armelin, Paulo Roberto [UNIFESP]; Renno, Ana Claudia Muniz [UNIFESP]Bioactive Glasses (BG) is a group of synthetic silica-based materials with the unique ability to bond to living bone and can be used in bone repair. Although the osteogenic potential of BG, this material may have not present sufficient osteoconductive and osteoinductive properties to allow bone regeneration, especially in compromised situations. In order to overcome this limitation, it was proposed the combination the BG in two forms (powder and fiber) combined with collagen type I (COL-1). The aim of this study was to evaluate the BG/COL-based materials in terms of morphological characteristics, physicochemical features and mineralization. Additionally, the second objective was to investigate and compare the osteoconductive properties of two different bioactive glass forms (powder and fiber) enriched or not with collagen using a tibial bone defect model in rats. For this, four different formulations (BG powder -BGp, BG powder enriched with collagen - BGp/Col, BG fibers - BGf and BGp fibers enriched with collagen - BGf/Col) were developed. The physicochemical and morphological modifications were analyzed by SEM, FTIR, calcium assay and pH measurement. For in vivo evaluations, histopathology, morphometrical and immunohistochemistry were performed in a tibial defect in rats. The FTIR analysis indicated that BGp and BGf maintained the characteristic peaks for this class of material. Furthermore, the calcium assay showed an increased Ca uptake in the BG fibers. The pH measurements revealed that BGp (with or without collagen) presented higher pH values compared to BGf. In addition, the histological analysis demonstrated no inflammation for all groups at the site of the injury, besides a faster material degradation and higher bone ingrowth for groups with collagen. The immunohistochemistry analysis demonstrated Runx-2 and Rank-L expression for all the groups. Those findings support that BGp with collagen can be a promising alternative for treating fracture of difficult consolidation. (C) 2017 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosPoly(3-hydroxybutyrate-co-valerate)/poly(3-thiophene ethyl acetate) blends as a electroactive biomaterial substrate for tissue engineering application(Royal soc chemistry, 2016) Recco, M. S. [UNIFESP]; Floriano, A. C. [UNIFESP]; Tada, D. B. [UNIFESP]; Lemes, A. P. [UNIFESP]; Lang, R. [UNIFESP]; Cristovan, F. H. [UNIFESP]Polyblends of an electroactive biomaterial consisting of a biodegradable polyester - PHBV and a carboxylate polythiophene derivative, the poly(3-thiophene ethyl acetate) - PTAcEt have been prepared and applied as a substrate for tissue engineering. The biodegradable polymer was used as a matrix for polythiophene. Thermal, electrical, optical and morphological properties as well as viability and cell adhesion (in vitro assays) were investigated. Blend films exhibited high flexibility, resistance to handling and a semiconducting character, since they preserved the individual properties of each polymer. Besides, the incorporation of PTAcEt (up to 12%) has led to improvements in the thermal stability and in the crystallinity degree of the bioactive matrix. Qualitative morphological analysis showed irregular and porous surfaces
- ItemSomente MetadadadosPorous poly (D,L-lactide-co-glycolide) acid/biosilicate((R)) composite scaffolds for bone tissue engineering(Wiley-Blackwell, 2017) Kido, Hueliton Wilian [UNIFESP]; Brassolatti, Patricia; Tim, Carla Roberta [UNIFESP]; Gabbai-Armelin, Paulo Roberto [UNIFESP]; Magri, Angela Maria Paiva [UNIFESP]; Fernandes, Kelly Rossetti [UNIFESP]; Bossini, Paulo Sergio; Parizotto, Nivaldo Antonio; Crovace, Murilo Camuri; Malavazi, Iran; Cunha, Anderson Ferreira da; Plepis, Ana Maria de Guzzi; Anibal, Fernanda de Freitas; Renno, Ana Claudia Muniz [UNIFESP]This study evaluated the effects of the Biosilicate((R)) and poly (D,L-lactic-co-glycolic) acid composites on bone repair in a tibial bone defect model in rats by means of using histological evaluation (histopathological and morphometric analysis) and gene expression analysis. Eighty male Wistar rats (12weeks old, weighing +/- 300g) were randomly divided into two groups: Biosilicate((R)) group (BG) and Biosilicate((R))/PLGA group (BG/PLGA). Each group was euthanized at 3, 7, 14, and 21days after surgery (n=10 animals per time point). The main findings showed that the incorporation of PLGA into BG had a significant effect on the morphological structure of the material, accelerating mass loss, decreasing the pH and increasing the calcium release. Furthermore, histologic analysis revealed that the BG/PLGA showed increased material degradation, accompanied by higher bone formation compared to BG, after 21days of implantation. In addition, qRT-PCR analysis showed that BG/PLGA induced an upregulation of the osteogenic genes related to BMP4, Runx2, ALP, and OC. These results show that the present BG/PLGA composite may be used as a bone graft for inducing bone repair. (c) 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 63-71, 2017.
- ItemAcesso aberto (Open Access)Síntese e Caracterização deTiO2 Puro e TiO2 Modificado com Zr-MOF: Potencial para Aplicação em Células Solares(Universidade Federal de São Paulo, 2022-12-15) Oliveira, Karine Vilares de [UNIFESP]; Mazzo, Tatiana Martelli [UNIFESP]; Trindade, Leticia Guerreiro da; lattes.cnpq.br/1719450522307763; http://lattes.cnpq.br/8843091201331133; http://lattes.cnpq.br/7831466203961554; Universidade Federal de São Paulo (UNIFESP)Impactos causados pela revolução industrial e a crescente preocupação com as questões ambientais fomentam a procura por matrizes energéticas sustentáveis. Diante deste desafio a energia fotovoltaica apresenta grande potencial para o fornecimento de energia limpa. A fim de obter maior eficiência ao menor custo possível a procura por materiais que atendam esses critérios vêm sendo pesquisados e testados. O dióxido de titânio (TiO2) apresenta grande potencial semicondutor, no entanto possui limitada capacidade de absorção de luz. As MOFs (metal-organic frameworks) possuem características promissoras para a melhora da atividade fotovoltaica do TiO2. O presente trabalho teve como objetivo analisar o potencial fotovoltaico do TiO2 puro e modificado com Zr-MOF através da síntese e caracterização destes materiais. O método utilizado para a síntese do TiO2 foi o sol-gel por apresentar vantagens como a obtenção de um material mais homogêneo e puro e com poucos defeitos cristalinos. Para a síntese do Zr-MOF utilizou-se o método solvotérmico que também oferece benefícios como a obtenção de partículas com maior uniformidade em sua composição e não requerer tratamentos térmicos a altas temperaturas posteriormente à síntese. Os materiais foram caracterizados pelas técnicas de difração de raios X (DRX), microscopia eletrônica de varredura com emissão de campo (MEV-FEG) e a propriedade fotoeletroquímica foi avaliada por voltametria linear (VL) e espectroscopia de impedância eletroquímica (EIE). A técnica de DRX mostrou que os métodos de síntese utilizados foram eficientes para obtenção dos materiais livres de fase secundárias, pela microscopia nota-se que foram obtidas nanopartículas sendo o TiO2 no formato esférico e aglomerado e o Zr-MOF no formato octaédrico, pela VL e pela EIE observou-se que o material TiO2 quando modificado com a inserção de 50% de Zr-MOF ocasiona melhoria significativa em sua propriedade fotoeletroquímica.