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(1,3trimethylene carbonate) (PTMC) coatings without cross-linking were prepared and used as control. Our results show that the crosslinked PMT coatings exhibited superior mechanical properties compared with PLLA and PTMC coatings. Meanwhile, the surfaceerosion 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.

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Herein, a hydrophobized zwitterionic-based copolymer poly­(sulfobetaine methacrylate-co-2-(dimethylamino)­ethyl methacrylate-co-isobornyl acrylate) (P­(SBMA-co-DMA-co-ISA), PSDI) containing a chiral structure has been successfully synthesized by free radical polymerization and subsequent sulfonation reactions. Together with tannic acid (TA), PSDI colloidal particles (CPs) were anchored onto the Ti alloy surface by the electrophoretic deposition method. The composition, morphology, and surface properties of the CP-TA composite coatings were characterized by  fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), optical contact angle (OCA), and other methods. The results show that the introduction of TA improves the stability of coatings by participating in the noncovalent interactions including ionic pairing and hydrogen bonding. According to the in vitro bacterial adhesion test, the modified titanium surface containing SBMA and chiral ISA functional units can effectively inhibit Gram-negative bacteria (E. coli) and Gram-positive bacteria (S. aureus) adhesion. Furthermore, the excellent cytocompatibility and favorable cell adhesion and growth behavior of zwitterionic-based coatings were realized as a result of the appropriate hydrophobicity provided by the ISA moiety. This work provides a new strategy for preparing zwitterionic-based multifunctional coating. The coating with excellent bacterial and cell selective adhesion properties has great potential in the applications of metal implant materials, such as cardiovascular stents and human hard tissue repair and replacement materials.

The zinc-alloy stent is one of the best potential candidates for bioabsorbable metal stents because of its appropriate corrosion rate aligned to the duration of the healing process of surrounding...

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