Synergistic coating strategy combining photodynamic and photothermal properties along with reinforcing corrosion protection fabricated on magnesium alloys

Postoperative infections of bone implants and loss of mechanical strength due to the corrosion are two major obstacles in the pathway for the magnesium alloys applications in biomedical region. To resolve above issues, a novel hybrid coating, MAO/EPR/Gel, is prepared on AZ31B magnesium alloys, in which the photodynamic therapy (PDT) and photothermal therapy (PTT) agents are combined together to form Er@PDA-RB and they are inserted in the micropores of micro-arc oxidation (MAO) coating rather than doping in it. The gelatin is utilized to prevent the leaking of Er@PDA-RB and it would be decomposed spontaneously in the human body. The |Z|(0.01 Hz) of MAO/EPR and MAO/EPR/Gel are 4.35 x 10(4) Omega cm(2) and 6.99 x 10(4) Omega cm(2), which is much larger than that of MAO coating and bare AZ31B Mg alloy with the values of 3.70 x 10(4) Omega cm(2) and 1.50 x 10(3) Omega cm(2), respectively. The antibacterial ratio for E. coli reaches 93.9 % under 980 nm near-infrared (NIR) irradiation within 60 min. Moreover, the MAO/EPR/Gel coating displays the excellent cytocompatibility with the HL-7702 cell viability > 75 % with or without 980 nm NIR irradiation. This multifunctional integrated coating accomplishes both PDT and PTT functions with only one NIR irradiation without sacrificing the anti-corrosion feature, which exhibits a promising application for magnesium alloys in biomedical applications.