Highly crosslinked ultrahigh molecular weight polyethylene (UHMWPE) stabilized by vitamin E (VE) is widely applied in artificial joints as the bearings. Despite the approval, there is a discord that VE lowers the crosslinking efficiency, limiting its use at high concentration. In this work, we aim to obtain highly crosslinked and oxidation resistant UHMWPE through the conjunction of tea polyphenol and chemical crosslinking. We hypothesized that highly incorporated tea polyphenol with multiple reactive sites can ameliorate crosslinking efficiency of chemical crosslinked UHMWPE in comparison to VE. Epigallocatechin gallate (EGCG) as representative tea polyphenol was incorporated into UHMWPE at high concentration (2–8 wt%), followed by chemical crosslinking with 2 wt% organic peroxide. Unlike VE/UHMWPE blends as the control, chemical crosslinking achieved an increasing trend in crosslink density of EGCG/UHMWPE blends with increasing antioxidant concentration. High concentration of EGCG also enhanced the oxidation stability of UHMWPE. Intriguingly, EGCG endowed UHMWPE with an excellent antimicrobial property, which was inefficient in VE/UHMWPE. Cell viability was hardly affected by the high loaded antioxidant and peroxide. The chemically crosslinked UHMWPE blended with EGCG is proved to be a reasonable, cost effective and realistic alternative for use in artificial joints.
ABSTRACT:The structure development and mechanical properties of blow extruded polypropylene containing b-phase nucleating additives was studied. Quinacridone red and cadmium red were both found to nucleate the b phase in polypropylene, the former being a much more efficient nucleator than the latter. The b-phase spherulites formed in the presence of these nucleating agents were small and extensively volume filled, yielding high crystallinity. The modulus increased 2-3 times, elongation at break decreased, and there was a sharp break point without much yield when the b-phase nucleating agents were added as compared to the pure a-phase polypropylene.
Vitamin E (VE) is currently an approved antioxidant to improve the oxidation stability of highly crosslinked ultrahigh molecular weight polyethylene (UHMWPE) insert used commercially in total joint arthroplasty. However, the decrease in crosslink density caused by VE reduces wear resistance of UHMWPE, showing an uncoordinated challenge. In this work, we hypothesized that D-sorbitol (DS) as a secondary antioxidant can improve the antioxidant efficacy of VE on chemically crosslinked UHMWPE. The combined effect of VE and DS on oxidation stability of UHMWPE was investigated at a set of controlled hybrid antioxidant content. The hybrid antioxidant strategy showed significantly synergistic enhancement on the oxidation stability of chemically crosslinked UHMWPE compared with the single VE strategy. More strikingly, the crosslink density of the blends with hybrid antioxidants stayed at a high level since DS is not sensitive to crosslinking. The relationships between oxidation stability, mechanical properties, crosslink density, and crystallinity were investigated, by which the clinically relevant overall performance of UHMWPE was optimized. This work provides a leading-edge design mean for the development of joint bearings.
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