Effect of Hydroxyapatite Post-Treatment on the Corrosion Resistance, Cytocompatibility and Antibacterial Properties of Copper-Containing Micro Arc Oxidation Coatings on Mg Alloy as Oral GBR Membrane Application

Biodegradable magnesium (Mg) alloys hold promising application prospects in the field of guided bone regeneration (GBR) membranes, particularly for oral and maxillofacial applications. However, their corrosion resistance requires further improvement. Additionally, Mg alloys are susceptible to bacterial infection upon implantation, while copper (Cu) is known for its excellent antibacterial properties. Introducing Cu into the micro-arc oxidation (MAO) coating can enhance both the corrosion resistance and antibacterial performance of Mg alloys. However, the sealing effect of such coatings remains suboptimal. Hydroxyapatite (HA), which possesses outstanding bioactivity, is a promising bone substitute material. This study investigates the influence of HA content on the microstructure, corrosion resistance, cytotoxicity, and antibacterial properties of Cu-containing MAO coatings. The results demonstrate that as the HA concentration increases, the corrosion resistance of the composite coating is significantly enhanced. The corrosion rate decreased from 0.32 mm/y for the untreated MAO coating to 0.27 mm/y and 0.23 mm/y for the HA-treated samples with EDTA–Ca concentrations of 125 mmol/L and 175 mmol/L, respectively. Cytotoxicity assessment indicates that the incorporation of an HA layer significantly improves cell compatibility compared to the bare MAO coating. However, the enhanced corrosion resistance provided by the denser HA layer (at 175 mmol/L EDTA–Ca) unfortunately acts as a barrier, limiting the release of antibacterial Cu2+. Among the coatings tested, the one with 125 mmol/L EDTA–Ca exhibited the best overall performance, demonstrating good corrosion resistance, cytocompatibility, and effective antibacterial properties.