PU/ZnO composites for biomedical applications

• Autor(a) principal: Luís, Jorge Louro
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/8175
• topic: Engenharia de materiais; Nanocompósitos - Aplicações biomédicas; Óxido de zinco; Poliuretanos

The present work is focused on the preparation and characterization of biomedical devices able to elicit different biological responses. Polyurethane/zinc oxide composites (PU/ZnO) appear as very promising materials as they may combine the interesting biomedical properties of ZnO and PU. However the properties of the composites, particularly in what the biological response is concerned, are far from being completely known. They are even unpredictable when ZnO nanoparticles or nanostructures are involved as ambiguous behaviours have been pointed out to nanometric sized ZnO particles. The main objective of the present work is to study the effects of the shape, size and concentration of ZnO particle on the properties of PU/ZnO composites, particularly on its bioactivity and cellular response. For this purpose ZnO nanoparticles/nanostructures were synthesized by a chemical precipitation method and subsequently characterized in terms of crystal phase composition, crystallinity, shape and particle size, specific surface area and porosity. These properties were further compared to those of commercial ZnO nanoparticles counterparts. PU/ZnO composites were then formulated by loading a PU matrix with ZnO particles (2 and 50%wt) and then submitted to in vitro bioactivity tests in SBF and to cell viability assays using a MC3T3 cell line. The bioactivity assays revealed that 50%wt ZnO loaded composites, namely those loaded with ZnO nanospheres, are potentially more bioactive than both PU and 2%wt PU/ZnO composites. Regarding cell viability, 2%wt PU/ZnO formulations were found to be the composites ensuring the higher cell viability. It was also shown that the toxicity effects of the 50%wt PU/ZnO composites prepared either with commercial or precipitated nanostructured ZnO particles were very similar to the toxicity effects of the corresponding isolated ZnO particles. As for the composites prepared with ZnO nanospheres (50%wt Pu/ZnO), their toxicity was higher than the remaining composites. These behaviours were discussed based on Zn2+ release to SBF media. As a conclusion, the obtained results show that it is possible to control PU/ZnO composites bioactivity and cytotoxicity by manipulating the concentration and/or ZnO particle morphology, thereby enabling the design of composites with potential usefulness for orthopaedic applications (2 %wt PU/ZnO) or for biomedical purposes intended to retard cellular proliferation like cancer treatment (50 %wt PU/ZnO).