No abstract

In this work, the preparation and characterization of membranes obtained through chitosan and alginate coacervation and designed for use as wound dressings were evaluated. The influence of different stirring rates and rates of addition of chitosan solution to alginate solution on the final characteristics of the biomaterial was analyzed in detail, aiming at a simple and easily scalable membrane production protocol. The results show that membranes with dry thickness from 66 to 80 lm, wet thickness from 106 to 633 lm, tensile strength varying from 6.86 to 31.14 MPa, elongation at break from 3.97 to 8.42%, and maximum water uptake up to 19 g of water per gram of membrane and that are able to prevent the permeation of bacteria can be obtained in a fairly reproducible way by the procedure established. The membranes prepared at flow ratio of 40 mL/h and stirring equal to 100 rpm showed a high potential for use on highly exuding wounds.

Resumo: Neste trabalho foi avaliada a influência do tratamento de fibras de bagaço de cana-de-açúcar nas propriedades mecânicas e dinâmico-mecânicas, na estabilidade térmica, na densidade e absorção de água, quando utilizadas na preparação de compósitos com resinas de poliéster insaturado em comparação com a resina sem reforço. As fibras foram submetidas a tratamento químico com solução alcalina de hidróxido de sódio. O tratamento melhorou as propriedades de impacto, aumentou o módulo de elasticidade em flexão, não alterou significativamente o módulo de elasticidade em tração dos compósitos em relação à resina sem reforço e melhorou a compatibilidade fibra matriz quando comparada com compósitos com a fibra sem tratamento, o que pode ser observado nas fraturas de impacto analisadas por microscopia eletrônica de varredura. As superfícies das fibras também foram avaliadas por microscopia eletrônica de varredura. Palavras-chave: Resina de poliéster insaturado, bagaço de cana-de-açúcar, mercerização, propriedades mecânicas, propriedades dinâmico-mecânicas, adesão fibra-matriz. Unsaturated Polyester Resin Composite with Sugar Cane Bagasse: Influence of Treatment on the Fibers Properties Abstract: The aim of this work is to evaluate the influence of the sugar cane bagasse NaOH treatment in the mechanical and dynamic-mechanical properties, in the thermal stability, density and water absorption, when used in unsaturated polyester resin/sugar cane bagasse composite. The sugar cane bagasse was submitted to the chemical treatment with alkaline solution of NaOH. The treatment improves the impact and flexural elasticity modulus when compared with resin without fibers, in addition to the adhesion of the fibers with the matrices, but does not improve significantly the tensile elasticity modulus. The surfaces of the impact fracture were analyzed by SEM. Keywords: Unsaturated polyester resin, sugar cane bagasse, mercerization, mechanical properties, dynamic mechanical properties, fiber-matrix adhesion. IntroduçãoAtualmente muitas pesquisas têm avaliado a viabilidade da utilização de fibras naturais como uma alternativa para as fibras sintéticas convencionalmente utilizadas como reforço em materiais compósitos de matriz polimérica. Este interesse se deve à necessidade de se encontrar fontes renováveis de matéria-prima, de reduzir o impacto ambiental dos materiais e reduzir custos [1][2][3][4][5][6][7][8][9][10] . Fibras celulósicas como bagaço de cana-de-açúcar, sisal, banana, coco, madeira e juta, têm sido incorporadas em vários termoplásticos e termofixos como reforço ou carga [11] . As resinas termofixas são muito empregadas devido às diversas vantagens como: baixo custo, estabilidade térmica e dimensional, resistência química a altas temperaturas e facilidade de se moldar peças com grandes dimensões; no entanto a sua baixa resistência à fratura torna necessária a utilização de reforços.Joshi et al. avaliaram o ciclo de vida de compósitos com diferentes fibras naturais em relação a um compósito com fibras de vidro e chegara...

Tissue engineering aims at creating biological body parts as an alternative for transplanting tissues and organs. A current new approach for such materials consists in injectable biodegradable polymers. Their major advantages are the ability to fill-in defects, easy incorporation of therapeutic agents or cells, and the possibility of minimal invasive surgical procedures. Polycaprolactone (PCL) is a promising biodegradable and elastic biomaterial, with the drawback of low-degradation kinetics in vivo. In this work a biodegradable injectable gel of PCL blended with sebacic acid (SA) was prepared, to improve the degradation rate of the biomaterial. SA is known for its high degradation rate, although in high concentrations it could originate a pH decrease and thus disturb the biocompatibility of PCL. Degradation tests on phosphate buffered saline were carried out using 5% of SA on the blend and the biomaterial stability was evaluated after degradation using differential scanning calorimetry, dynamical mechanical analysis, and scanning electronic microscopy. After degradation the elastic properties of the blend decreased and the material became more crystalline and stiffer, although at a lower extent when compared with pure PCL. The blend also degraded faster with a loss of the crystalline phase on the beginning (30 days), although its thermal and mechanical properties remained comparable with those of the pure material, thus showing that it achieved the intended objectives. After cell assays the PCL-SA gel was shown to be cytocompatible and capable of maintaining high cell viability (over 90%).

Tissue engineering constitutes a promising alternative technology to transplantation medicine by creating viable substitutes for failing tissues or organs. The ability to manipulate and reconstitute tissue function has tremendous clinical implications and will most likely play a key role in cell and gene therapies in the coming years. In the present work, a novel injectable and biodegradable biomaterial is reported that could be injected on the human body with a surgical syringe. The material prepared is a blend of polycaprolactone (PCL), a biodegradable and elastic biomedical polymer, and sebacic acid, a natural polymer part of castor oil with low molecular weight to accelerate the slow degradation rate of PCL. The biocompatibility of the blend was evaluated in vitro and its in vivo behavior was also assessed through subcutaneous and bone implantation in rats to evaluate its tissue-forming ability and degradation rate. The results allowed the conclusion that the gel is biocompatible, promotes the differentiation of mesenchymal stem cells, and presents an adequate degradation rate for use in bone tissue engineering. In vivo the gel blends promoted tissue regeneration and adverse reactions were not observed on subcutaneous and bone implants.