Multi-functional composite coatings for magnesium alloys integrating photodynamic, photothermal and anti-corrosion

• A multifunctional coating was fabricated on AZ31 Mg alloy via a synergistic strategy. • The coating enables simultaneous PDT and PTT under a single 980 nm NIR laser. • The coating achieves >99 % antibacterial efficiency against Escherichia coli via dual PDT/PTT. • The coating exhibits enhanced corrosion resistance with favorable biocompatibility. Magnesium alloys hold great promise for medical applications due to their high biocompatibility and mechanical properties. However, their rapid corrosion in the body and susceptibility to infections pose significant challenges. To address these issues, we developed a multifunctional MAO/F/ETPR/Gel composite coating on AZ31B magnesium alloy. This coating integrates photothermal agents (FePC) and ErTm@PDA-RB nanoparticles within a micro-arc oxidation (MAO) layer, sealed with a gelatin layer. After the MAO/F/ETPR/Gel coating is applied to the magnesium alloy, the corrosion current density decreases by about two orders of magnitude, demonstrating markedly improved corrosion resistance. Compared with bare magnesium alloy, the coating demonstrates improved antibacterial properties with an antibacterial rate of 99.15 % against Escherichia coli under 980 nm light irradiation. Additionally, it exhibits minimal cytotoxicity to HL-7702 human liver cells, confirming its biocompatibility. This innovative coating combines photodynamic and photothermal therapies, activated by a single near-infrared light source, to address the challenges of rapid degradation and postoperative infections. Our study provides a novel solution for enhancing the performance of magnesium alloy implants in biomedical applications.