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

Exportado OPUSMade available in DSpace on 2019-08-09T14:07:02Z (GMT). No. of bitstreams: 1 regina_coeli_moreira_dias.pdf: 3766480 bytes, checksum: 6896fd886c0c8b86ab3bb4e518e6acd2 (MD5) Previous issue date: 7Biomateriais para aplicacoes ligadas a Engenharia de Tecidos usualmente requerem uma serie de caracteristicas: presenca de poros grandes e com elevada interconectividade, biodegradabilidade, elevadas propriedades mecanicas, bioatividade, citocompatibilidade, entre outras. Neste trabalho, uma nova matriz para a Engenharia de Tecidos foi desenvolvida e preliminarmente testada in vitro e in vivo. Este novo sistema consistiu em uma matriz de poliuretano biodegradavel (derivado de policaprolactona) contendo nanoparticulas derivadas de argilas. O material foi avaliado por FTIR, difracao de raios-x e microscopia eletronica. Testes in vitro foram realizados atraves do estudo da colonizacao do material por osteoblastos via uso de ensaios como: tetrazolium (MTT), expressao de colageno e fosfatate alcalina. As matrizes obtidas foram ainda implantadas em camundongos e foi realizada analise histologica em amostras removidas apos 14 e 29 dias. Os resultados mostraram que a porosidade, obtida atraves da reacao do poliuretano com agua, foi bem sucedida em produzir poros conectados e com tamanhos entre 184Êm - 327Êm. Espectros de FTIR mostraram a formacao com sucesso de uma rede de poliuretano contendo nanoparticulas. A difracao de raios-x mostrou que as nanoparticulas no material se apresentaram parcialmente esfoliadas e ainda atuaram como sitios nucleadores da cristalizacao do poliuretano. Testes in vitro mostraram que a matriz porosa de poliuretano foi bem sucedida em permitir a fixacao e crescimento de osteoblastos. Os resultados dos testes in vivo tambem confirmaram os resultados in vitro, mostrando a ausencia de um processo inflamatorio prolongado. Alem disso, as fotos obtidas por microscopia eletronica mostraram uma grande invasao celular atraves dos poros abertos da matriz, levando a uma total colonizacao. Modificacoes na superficie do poliuretano atraves da imobilizacao de peptideos e glicosaminoglicanas levaram a altos niveis de toxidade detectados tanto in vitro como in vivo, mostrando que os procedimentos quimicos usados foram agressivos o suficiente para produzir estruturas polimericas parcialmente degrada e toxicas.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.

Porous biodegradable polyurethane nanocomposites: preparation, characterization, and biocompatibility tests

A porous biodegradable polyurethane nanocomposite based on poly(caprolactone) (PCL) and nanocomponents derived from montmorillonite (Cloisite®30B) was synthesized and tested to produce information regarding its potential use as a scaffold for tissue engineering. Structural and morphological characteristics of this nanocomposite were studied by infrared spectroscopy (FTIR), X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). The reaction between polyurethane oligomers with isocyanate endcapped chains and water led to the evolution of CO2, which was responsible for building interconnected pores with sizes ranging from 184 to 387 μm. An in vitro cell-nanocomposite interaction study was carried out using neonatal rat calvarial osteoblasts. The ability of cells to proliferate and produce an extracellular matrix in contact with the synthesized material was assessed by an MTT assay, a collagen synthesis analysis, and the expression of alkaline phosphatase. In vivo experiments were performed by subcutaneously implanting samples in the dorsum of rats. The implants were removed after 14, 21, and 29 days, and were analyzed by SEM and optical microscopy after tissue processing. Histology crosssections and SEM analyses showed that the cells were able to penetrate into the material and to attach to many location throughout the pore structure. In vitro and in vivo tests demonstrated the feasibility for polyurethane nanocomposites to be used as artificial extracellular matrices onto which cells can attach, grow, and form new tissues