A Micro-arc Oxidation/Poly(1,3-Trimethylene Carbonate) Hybrid Coating for Anticorrosion and Hemocompatibility Enhancement of High-Purity Magnesium

Magnesium (Mg) and its alloys possess good mechanical support and biodegradability, exhibiting enormous potential in the field of vascular stents. However, the rapid degradation results in premature loss of mechanical support and triggers adverse interactions such as hemolysis. The purpose of this work is to establish a hybrid coating that combines organic and inorganic materials to reduce the degradation rate of Mg. Initially, the micro-arc oxidation (MAO) process is employed to fabricate an inorganic layer on a high-purity magnesium (PM) substrate. Subsequently, a solvent evaporation method is utilized to create an organic layer of the elastic poly(1,3-trimethylene carbonate) (PTMC) polymer to seal the pores of the MAO layer. The results show that the Young's modulus of PM modified with the MAO/PTMC hybrid coating (PM/M/P) decreases from 40.3 ± 5.7 to 0.2 ± 0.1 GPa representing a reduction of nearly 200 times. The corrosion current density of PM/M/P drops to 0.3 ± 0.1 μA cm⁻², 436 times smaller than that of PM (130.9 ± 6.2 μA cm⁻²) in the simulated body fluid (SBF). The immersion results also confirm that the MAO/PTMC coating effectively mitigates the degradation rate, as evidenced by the minimal alteration of pH in the SBF and the lowest level of released H₂. In addition, the in vitro hemocompatibility results indicate that compared to the bare PM, PM/M/P reduces the hemolysis rate remarkably to the safe range and platelet accumulation on the surface. Based on these findings, the hybrid coating fabricated on PM is promising to facilitate the clinical application of Mg-based vascular stents.