High corrosion resistance and cytocompatibility of zinc phosphate coating on pure zinc achieved by incorporating a trace amount of MXene nanosheets for orthopedic implants

Biodegradable zinc (Zn) alloys hold significant promise for bone implant applications owing to their tunable degradation rates and multi-biofunctional properties. However, the low tolerance of osteoblasts to Zn 2+ ions renders high cytotoxic of all uncoated Zn alloys. To address this, zinc phosphate (ZnP) coatings are frequently applied to Zn-based biomaterials to enhance biocompatibility and control Zn 2+ release; however, these coatings often exhibit unstable corrosion resistance. This study introduces MXene, a two-dimensional nanomaterial with a unique layered structure, to overcome this limitation. We systematically investigated the effect of different MXene concentrations (0.00, 0.04, 0.08, and 0.12 g/L) on the corrosion resistance and cytocompatibility of ZnP coatings on pure Zn substrates. Experimental results demonstrate that MXene promotes the phosphatization reaction, facilitating the formation of finer grains. This refinement of the coating microstructure yields a denser and more uniform ZnP layer, which significantly improves corrosion resistance. The coating modified with 0.08 g/L MXene showed optimal performance in both short-term electrochemical tests and long-term immersion experiments. Furthermore, the MXene-enhanced ZnP coating supported higher cell viability of MC3T3-E1 osteoblast cells after 3-day culture, confirming that the improved corrosion protection is coupled with enhanced cytocompatibility.