Fabrication of Zn²⁺-Loaded Polydopamine Coatings on Magnesium Alloy Surfaces to Enhance Corrosion Resistance and Biocompatibility

In this study, inspired by the adhesion protein of mussels, a Zn2+-loaded polydopamine (PDA/Zn2+) coating was prepared on an alkali-heat-treated magnesium alloy surface, through the chelating effect of PDA with metal ions, to improve anticorrosion and biocompatibility. The results of water contact angles show that the PDA/Zn2+ coatings with different Zn2+ contents had excellent wettability, which contributed to the selective promotion of the albumin adsorption. The corrosion degradation behaviors of the modified magnesium alloys were characterized using potentiodynamic scanning polarization curves, electrochemical impedance spectroscopy (EIS), and an immersion test, the results indicate that anticorrosion was significantly improved with the increase of Zn2+ content in the coating. Meanwhile, the PDA/Zn2+ coatings with different Zn2+ concentrations demonstrated improved hemocompatibility, confirmed by assays of the hemolysis rate and platelet adhesion behaviors. In addition, the results regarding the growth behaviors of endothelial cells (ECs) suggest that, due to the sustained release of Zn2+ from the coatings, the modified magnesium alloys could enhance the adhesion, proliferation, and upregulated expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in endothelial cells, and that better cytocompatibility to ECs could be achieved as the Zn2+ concentration increased. Therefore, the PDA/Zn2+ coatings developed in this study could be utilized to modify magnesium alloy surfaces, to simultaneously impart better anticorrosion, hemocompatibility, and endothelialization.