Study on the regulation of copper in the degradation resistance, antibacterial, and osteogenic properties of micro-arc oxidation coatings on magnesium alloy

Abstract

Magnesium alloys, among the most promising biomaterials for orthopedic applications, face challenges with post-implantation infection. Copper offers potent antibacterial activity while exhibiting low biotoxicity at appropriate concentrations. This study investigated the incorporation of copper oxide nanoparticles into micro-arc oxidation (MAO) electrolytes to develop a coating combining enhanced antibacterial performance with improved corrosion resistance for Mg alloys. We systematically examined the influence of Cu content on the microstructure, corrosion resistance, antibacterial efficacy, cytotoxicity, and osteogenic properties of the coated Mg alloy samples. Electrochemical tests demonstrated that MAO coatings incorporating 1 g/L and 3 g/L CuO significantly enhanced corrosion resistance, and the corrosion rates were reduced to 0.16 mm/y and 0.38 mm/y, respectively. In immersion tests, the lowest corrosion rate of 0.31 mm/y was recorded for the 1 g/L CuO coating, which represents a 40% reduction compared to the 0 g/L CuO coating. However, further increases in CuO concentration degraded the coating’s protective properties. Antibacterial assays revealed excellent efficacy against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) for coatings containing ⩾3 g/L CuO. In vivo animal testing indicated that the 3 g/L CuO MAO coating promoted optimal osteogenesis, with substantial new bone formation observed after 4 weeks in vivo. Based on the comprehensive in vitro and in vivo results, the MAO coating modified with 3 g/L CuO exhibited the greatest potential for orthopedic implant applications, offering a balanced combination of corrosion resistance, antibacterial activity, biocompatibility, and osteogenic capability.

Keywords

magnesium alloy / CuO / corrosion resistance / antibacterial property / osteogenic property

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