Oxidation of ultra high molecular weight polyethylene, UHMWPE, containing traces of cobalt ion

grantor: University of TorontoWear of metal and UHMWPE implant components generates sub-micron particles contaminated with metal ions. The associated particles have been shown to be phagocytosed by human macrophages. This thesis is focused on the study of UHMWPE particle degradation products and the process by which these products may be generated under simulated thermal and oxidative/hydrolytic pathways of the implant environment. Oxidation of particles was measured using Fourier transform infrared spectroscopy (FTIR). It was shown that metallic ion (i.e., cobalt) accumulation into the particles (at trace levels of 10 ppm) can dramatically accelerate their oxidative degradation at relatively low temperatures (i.e. 60°C). Degradation products were isolated using high performance liquid chromatography (HPLC) and characterized using liquid chromatography/mass spectrometry (LC/MS), mass spectrometry (MS/MS) and attenuated total reflectance FTIR (ATR-FTIR). The analysis of the isolated products showed that the degradation of the UHMWPE could be further propagated by the particle interaction with macrophage associated oxidants, such as H2O2. It is postulated that the generation of degradation products from phagocytosed UHMWPE particles and their uptake intra-cellularly could mediate cellular responses. Such considerations have not been previously investigated for implant derived UHMWPE particles.M.A.Sc