Síntese e caracterização de filmes e matrizes híbridas e nanocompósitas de quitosana e vidro bioativo

Abstract

Nanostructured scaffolds have generated promising results in bone tissue engineering. The production of composites bioactive glass/polymer have been the focus of studies in the literature, which have associated to the bioactive glass the capacity to form a strong bond with the bone tissue surface. One method for introducing the bioactive phase in composites has been the solgel method, leading to a hybrid or a nanocomposite material. The presence of the bioactive phase at the nanometer scale increases the bioactivity and, in addition, acts as an agent for improving the mechanical strength of the material. Among the polymers more frequently used, Chitosan shows promising results in the literature, because of its ability to biodegrade, its biocompatibility, and a high mechanical strength when combined with crosslinking agents. In this work composites bioactive glass/chitosan were developed using two strategies for introducing the bioactive phase: i) a precursor solution (sol) was added to the polymer solution (materials obtained heretofore called hybrids); ii) bioactive glass nanoparticles obtained previously by the solgel method was added to the polymer solution (materials obtained heretofore called nanocomposites). The main objective was to compare the films and porous matrices obtained when using the two different routes, in terms of chemical composition, porosity, pore morphology, mechanical behavior, bioactivity, and cytotoxicity. The FTIR results showed the presence of characteristic functional groups of bioactive glass, confirming its introduction into the polymeric network. Some composites, particularly those with higher glass content, showed significant bioactivity, confirmed through the formation of a surface layer with morphological characteristics typical of HCA, confirmed by DRX and FTIR. Most scaffolds obtained presented a homogeneous pore structure with interconnectivity, pore size distribution between 50 and 120m, and porosity ranging from 62 to 91%. Hybrids and nanocomposites obtained presented high mechanical strength, with values reaching the order of 80MPa for films and 11MPa for scaffolds, values significantly higher when compared to those shown by pure chitosan or composites based on silica and other polymers reported in the literature. The maximum deformation reached values in the order of 22% for films and 71% for scaffolds. In general the increase in strength obtained for the nanocomposites was more pronounced than for hybrids. Biological assays performed using human osteoblasts showed cell viability close to the control, confirming the low toxicity presented by the hybrids and nanocomposites materials developed.