Análise do envelhecimento acelerado e da ação inibidora do ácido ascórbico na degradação oxidativa do polietileno de ultra-elevada massa molar para aplicação biomédica

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is a biomaterial widely used as part of prosthesis that requires articulating surfaces for its excellent mechanical qualities such as knee endoprosthesis for its excellent mechanical qualities. Approximately one million UHMWPE components are implanted worldwide on yearly basis. Two major problems limit the UHMWPE prosthesis life wearing and delamination, both phenomena being mainly due to chemical oxidation of polymer. However, despite the intensive focus on ageing methodologies for UHMWPE over the last few years there are still remains muchdebate over the most effective way of accelerated ageing this material to simulate both shelf and in-vivo ageing. The aim of this study was to investigate and characterize by infrared absorption the accelerated degradation of UHMWPE under hydrogen peroxide aggressivemedium for long period of time as well as to determine the antioxidant capacity from ascorbic acid in UHMWPEs oxidation. In vitro tests to evaluate the macrophage response to test materials were performed in order to investigate as the chemical surface alters the inflammatory response. Our results showed that the hydrogen peroxide acted efficiently in the oxidation of UHMWPE. The measure of oxidation index, determined after different times, resulted in increased rates of oxidation. There was also a decrease of oxidative degradation of UHMWPE with the addition of ascorbic acid showing that vitamin C can act as a potent antioxidant agent for UHWMPE. Preliminary results for macrophage responsesuggest that there is a trend to increased nitric oxide secretion with the times oxidation, influencing by chemical surface of UHMWPE.