Enhancing the Antibacterial Properties of Magnesium Alloys with Copper-Doped Anhydrous Calcium Phosphate Nanoparticles Embedded into the Polycaprolactone Coating for Medical Implants

Magnesium alloys are ideal materials in clinical applications for their excellent mechanical properties, while potential cytotoxicity with rapid degradation limits their clinical applications. Moreover, it is also important for implants to avoid inflammation caused by bacterial infections in the early stage of implantation. Therefore, copper-doped anhydrous calcium phosphate nanoparticles were fabricated by the hydrothermal method and dispersed in a dicalcium phosphate dihydrate (DCPD)/Polycaprolactone (PCL) composite coating to improve its bacteriostatic properties, corrosion resistance, and biocompatibility in this paper. The impedance of the DCPD/PCL/Cu-doped anhydrous calcium phosphate (Cu-ADCP) composite-coated sample is 1 order of magnitude higher than that of the bare magnesium alloy, and the corrosion current density decreases by 2 orders of magnitude, indicating that the composite coating incorporating nanoparticles can effectively enhance the corrosion resistance. The in vitro cell experiments show its biocompatibility with sustained growth in cellular activity and increased alkaline phosphatase activity. Most importantly, the embedded copper-doped nanoparticles significantly improve the antibacterial properties of the composite coating. Compared with the composite coating with almost no antibacterial ability, the antibacterial rate reached 96 and 98% for Escherichia coli and Staphylococcus aureus, respectively, after the nanoparticles were embedded, making them a promising choice for orthopedic applications.