Poly(2-methacryloyloxyethyl phosphorylcholine) grafting and vitamin E blending for high wear resistance and oxidative stability of orthopedic bearings

• Published in: Biomaterials 2014-08, Vol.35 (25), p.6677-6686
• Main Authors: Kyomoto, Masayuki, Moro, Toru, Yamane, Shihori, Watanabe, Kenichi, Hashimoto, Masami, Takatori, Yoshio, Tanaka, Sakae, Ishihara, Kazuhiko
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; Antioxidant; Antioxidants - pharmacology; Bearings; Biocompatible Materials - chemistry; Blending; Cross-linked polyethylene; Dentistry; Dose-Response Relationship, Radiation; Gamma Rays; Grafting; Hip Prosthesis; Hydrophobic and Hydrophilic Interactions; Joint replacement; Materials Testing; Microscopy, Electron, Transmission; Nanostructures - chemistry; Oxidation; Phosphorylcholine; Phosphorylcholine - analogs & derivatives; Phosphorylcholine - chemistry; Polyethylene; Polyethylenes - chemistry; Polymerization; Polymethacrylic Acids - chemistry; Stability; Surface Properties; Ultraviolet Rays; Vitamin E; Vitamin E - chemistry; Vitamins; Wear mechanism
• ISSN: 0142-9612; 1878-5905
• DOI: 10.1016/j.biomaterials.2014.04.051

Abstract The ultimate goal in manipulating the surface and substrate of a cross-linked polyethylene (CLPE) liner is to obtain not only high wear resistance but also high oxidative stability and high-mechanical properties for life-long orthopedic bearings. We have demonstrated the fabrication of highly hydrophilic and lubricious poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) grafting layer onto the antioxidant vitamin E-blended CLPE (HD-CLPE(VE)) surface. The PMPC grafting layer with a thickness of 100 nm was successfully fabricated on the vitamin E-blended CLPE surface by using photoinduced-radical graft polymerization. Since PMPC has a highly hydrophilic nature, the water wettability and lubricity of the PMPC-grafted CLPE and HD-CLPE(VE) surfaces were greater than that of the untreated CLPE surface. The PMPC grafting contributed significantly to wear reduction in a hip-joint simulator wear test. Despite high-dose gamma-ray irradiation for cross-linking and further UV irradiation for PMPC grafting, the substrate modified by vitamin E blending maintained high-oxidative stability because vitamin E is an extremely efficient radical scavenger. Furthermore, the mechanical properties of the substrate remained almost unchanged even after PMPC grafting or vitamin E blending, or both PMPC grafting and vitamin E blending. In conclusion, the PMPC-grafted HD-CLPE(VE) provided simultaneously high-wear resistance, oxidative stability, and mechanical properties.