Probing the Influence of γ‑Sterilization on the Oxidation,Crystallization, Sliding Wear Resistance, and Cytocompatibility of Chemically Modified Graphene-Oxide-Reinforced HDPE/UHMWPEN a nocomposites and Wear Debris

Osteolysis and aseptic loosening due to wear at the articulating interfacesof prosthetic joints are considered to be the key concerns for implant failure in load-bearing orthopedic applications. In an effort to reduce the wear and processingdifficulties of ultrahigh-molecular-weight polyethylene (UHMWPE), our research grouprecently developed high-density polyethylene (HDPE)/UHMWPE nanocompositeswith chemically modified graphene oxide (mGO). Considering the importance ofsterilization, this work explores the influence ofγ-ray dosage of 25 kGy on the clinicallyrelevant performance-limiting properties of these newly developed hybrid nano-composites in vitro. Importantly, this work also probes into the cytotoxic effects of thewear debris of different compositions and sizes on MC3T3 murine osteoblasts andhuman mesenchymal stem cells (hMSCs). In particular,γ-ray-sterilized 1 wt % mGO-reinforced HDPE/UHMWPE nanocomposites exhibit an improvement in the oxidationindex (16%), free energy of immersion (−12.1 mN/m), surface polarity (5.0%), andhardness (42%). Consequently, such enhancements result in better tribological properties, especially coefficient of friction (+13%)and wear resistance, when compared with UHMWPE. A spectrum of analyses using transmission electron microscopy (TEM) and invitro cytocompatibility assessment demonstrate that phagocytosable (0.5−4.5μm) sterilized 1 mGO wear particles, when present inculture media at 5 mg/mL concentration, induce neither significant reduction in MC3T3 murine osteoblast and hMSC growth norcell morphology phenotype, during 24, 48, and 72 h of incubation. Taken together, this study suggests thatγ-ray-sterilized HDPE/UHMWPE/mGO nanocomposites can be utilized as promising articulating surfaces for total joint replacements