Effects of Manganese Oxide Content on the Corrosion Resistance and Cytotoxicity of Chitosan/Manganese Oxide Composite Coatings Sealed on Micro-Arc Oxidized Magnesium Alloy for Guided Bone Regeneration

Magnesium alloys are promising for biodegradable guided bone regeneration (GBR) membrane applications. But a limitation is fast corrosion. Micro-arc oxidation (MAO) coatings on Mg alloys were sealed with chitosan (CS) composite coatings containing varying MnO2 contents (0, 1, 3, 5 g/L; M0–M5). Microstructure, corrosion, wear, and cytocompatibility were evaluated. The results showed that M1 (1 g/L MnO2) exhibited the best corrosion resistance, with the lowest corrosion current density (2.06 μA/cm2) in Hank’s solution, which is six times better than with M0. Adding MnO2 is beneficial because it acts as a sealing agent to fill the micropores of the MAO coating. M1 also showed the least wear volume loss. Cell assays indicated that M1 had the highest relative growth rate (>95%) and alkaline phosphatase activity (~42 U/mg protein). Excessive MnO2 caused agglomeration and reduced performance. Thus, among the tested concentrations, 1 g/L MnO2 optimally enhances corrosion resistance, durability, and early osteogenic differentiation of CS/MAO coatings, demonstrating its promising potential as a base material for future GBR membrane applications.