Photo-Cross-Linked Polycarbonate Coating with Surface-Erosion Behavior for Corrosion Resistance and Cytocompatibility Enhancement of Magnesium Alloy.

Absorbable magnesium (Mg) materials are promising for medical implant applications. However, their corrosion rate and potential toxicity remain a challenge. Herein, a photo-cross-linked coating with suitable durability and unique surface-eroding behavior for enhancement of anticorrosion property and cytocompatibility of AZ31 Mg alloy was developed. The biodegradable allyl-functional polycarbonate, poly[(5-methyl-5-allyloxycarbonyl-1,3-propanediol carbonate)- co -(trimethylene carbonate)] [P(MAC- co -TMC), PMT], was first synthesized by ring-opening copolymerization. The PMT copolymer, pentaerythritol tetrakis(3-mercaptopropionate), and a photoinitiator were then applied on AZ31 Mg alloy by dip coating, and these films were cross-linked via the subsequent photoinitiated thiol-ene click reaction. The poly(l-lactide) (PLLA) and poly(1,3-trimethylene carbonate) (PTMC) coatings without cross-linking were prepared and used as control. Our results show that the cross-linked PMT coatings exhibited superior mechanical properties compared with PLLA and PTMC coatings. Meanwhile, the surface-erosion behavior of the cross-linked PMT coatings remained, as confirmed by scanning electron microscopy analysis. As a result, the cross-linked PMT-coated Mg alloy showed lower corrosion rates, better in vitro corrosion resistance, and much lower cytotoxicity, compared with bare Mg and ones coated with PLLA and PTMC coatings. Results indicate that the cross-linked PMT coatings with unique surface-erosion behavior and good cytocompatibility might be promising to improve the safety and success rate of Mg-based devices and implants.