Multistep Instead of One-Step: A Versatile and Multifunctional Coating Platform for Biocompatible Corrosion Protection.

Magnesium alloys have potential application in cardiovascular stents and orthopedic implants. However, the rapid corrosion rate of magnesium limits their clinical application. In order to improve the corrosion resistance and biocompatibility of the substrate, a protective coating is constructed by alternate immersing of MgZnMn alloy in epigallocatechin gallate (EGCG) and polyethyleneimine (PEI) solution. The conventional method is immersing magnesium alloy into a conversion solution by simple one-step immersion. In the present work, the EGCG/PEI coating is prepared by a novel alternate immersion method. The number of alternate immersions resulted in a different density of phenolic hydroxyl groups and amino groups on the surface. The corrosion resistance and bonding strength of the coating also varied with alternating immersion times. As the corrosion resistance and density of the functional groups varies, endothelial cells (ECs), smooth muscle cells (SMCs), osteoblasts, and macrophages showed a different growth state on EGCG/PEI coatings. In summary, this EGCG/PEI coating addressed the rapid corrosion rate of the magnesium alloy and can adjust its function by controlling the number of alternate immersions. The EGCG/PEI coating exhibited multifunctions: improved corrosion resistance, good compatibility with ECs and osteoblasts, and inhibition of SMC growth and inflammation, and the effective groups on the coating make it possible for further modification by grafting biomolecules. This is an effective method for preparing a multifunctional platform on biomedical magnesium alloys.