In vitro degradation of ultra high molecular weight polyethylene, UHMWPE, by oxidative and/or hydrolytic processes

grantor: University of TorontoThe wear of UHMWPE implants generates polymer and metal particulates which can be phagocytosed by human macrophages. This thesis focused on the study of polyethylene particulate degradation by modeling the oxidative and hydrolytic processes that are associated with phagocytic activities, specifically H$\sb2$O$\sb2$ and cholesterol esterase. As well, synergistic effects on UHMWPE degradation by metal contaminants and H$\sb2$O$\sb2$ were examined. Oxidation was measured using Fourier transform infrared spectroscopy (FTIR). Degradation products were isolated using high performance liquid chromatography and identified using mass spectroscopy, attenuated total reflectance FTIR and nuclear magnetic resonance. An initial assessment of the effect of cobalt-treated HDPE particles on human monocyte/macrophage cytokine (IL-1$\beta$, IL-6 and TNF-$\alpha$) release was performed. The chemical oxidation of UHMWPE particles was observed on particles that were pre-sensitized using thermal and $\gamma$-irradiation treatments. Several oligomeric products, including compounds that contained alkanes, alkenes and hydroxyls, were isolated. Cell viability studies with particles showed increased necrosis with increased severity of environmental oxidation conditions. Cytokine data were inconclusive due to donor culture variability and very low values after 48 hours of incubation.M.A.Sc