Long-term oxidative stability and tribological performance of tea polyphenol-stabilized ultra-high molecular weight polyethylene after 7 years of real-time shelf aging

Although antioxidants such as vitamin E (VE) and tea polyphenols have been employed to enhance the oxidation resistance of ultra-high molecular weight polyethylene (UHMWPE) for artificial joint applications, the long-term oxidative behavior of tea polyphenol-stabilized, crosslinked UHMWPE under real-time shelf aging remains insufficiently understood. In this study, the performance evolution of crosslinked UHMWPE containing VE, epigallocatechin gallate (EGCG), and lipid-soluble EGCG ( ls EGCG) was investigated after 7 years of real-time shelf storage. Notably, the EGCG-stabilized UHMWPE exhibited a markedly higher crosslink density (≥ 40% increase compared with the VE group) and superior tribological performance, with the coefficient of friction reduced by 16‒35%. Furthermore, it reduced the fraction of submicron wear particles (≤ 1 µm), lowering the potential risk of osteolytic inflammation. The enhanced stabilization efficacy of tea polyphenols, particularly EGCG, originates from their polyphenolic hydroxyl groups, which could effectively quench free radicals and preserve crosslink network during long-term storage. Overall, these findings demonstrate that tea polyphenols represent a durable and effective antioxidant strategy for UHMWPE, with significant potential to extend the clinical service life of joint implants.