Síntese,caracterização e avaliação preliminar de citotoxicidade da matriz porosa de nanocompósito biodegradavel

Abstract

Biomaterials for tissue engineering applications usually require a series of characteristics: presence of large and interconnected pores, biodegradability, high mechanical properties, cytocompatibility, bioactivity, among others. In this work, a novel scaffold for tissue engineering was developed and preliminarily tested by using in vitro and in vivo cytotoxicity assays. This new scaffold consisted of a biodegradable polyurethane matrix (derived from polycaprolactone) containing nanoparticles derivedfor clay minerals. The material was characterized by using FTIR, x-ray diffraction and electron microscopy. In vitro tests were performed by studying the colonization of the material by osteoblasts by using cellular viability and activity tests, such as tetrazolium (MTT) assay, collagen expression and alkaline phosphatase assay. The obtainedscaffold was also implanted in mice and histological analyses on samples explanted after 14 and 29 days were investigated by employing optical and electron microcopies. Results showed that the porosity, obtained by expanding the polyurethane by reacting it with water, was successful in producing interconnected pores averaging 184ìm -327ìm. FTIR spectra showed the successful formation of the polyurethane network and incorporation of nanoparticles. X-ray diffraction showed that the nanoparticles within the material were partially exfoliated and also acted as nucleation sites for the crystallization of the polyurethane. In vitro results showed that the polyurethane porousmatrix was well succeeded in allowing the fixation and growth of osteoblasts. In vivo results also confirmed in vitro tests by showing that no prolonged inflammation process could be detected. Moreover, in vivo electron micrographs proved that cells were able to migrate through the open pores of the scaffold leading to a complete cellular colonization of the material. Modifications of the polyurethane surface by immobilizingpeptides and glicosaminoglicans led to high levels of toxicity detected by both in vitro and in vivo tests, showing that the chemical procedures used were aggressive enough to cause partially degraded and toxic polymer structures..