A photocontrolled self-healing composite coating based on polycaprolactone for enhancing the corrosion resistance and antimicrobial properties of biodegradable magnesium alloys

A photocontrolled self-healing composite coating consisting of polycaprolactone (PCL) and Prussian blue nanoparticles loaded with paeonol and modified with polydopamine (Pae/PB@PDA) was prepared on the surface of biomedical magnesium alloys pretreated with polydopamine (PDA). Experimental results demonstrate that this composite coating significantly improves the corrosion resistance of magnesium alloys. Its corrosion current density decreased to 0.751±0.035 μA/cm², and the annual corrosion rate was only 0.52±0.01 mm/y, which is significantly better than that of a PCL coating only. Under the triggering of near-infrared light (808 nm, 1.0 W/cm²), the self-healing function of the PCL coating was significantly enhanced by the photothermal synergistic effect of PDA and PB. The corrosion current density of the repaired coating was 0.926±0.160 μA/cm², differing slightly from that of the original coating. In addition, the coating achieves an inhibition rate of over 99% against Escherichia coli and Staphylococcus aureus with paeonol and photothermal therapy (PTT). This study provides an integrated solution for degradable magnesium alloy implants that combines self-healing, long-lasting anti-corrosion and intelligent antibacterial functions. • A self-healing P-PCL/Pae/PB@PDA composite coating was prepared on Mg alloy. • P-PCL/Pae/PB@PDA composite coating exhibits excellent photothermal property. • Composite coating greatly improves the corrosion resistance of Mg alloy. • Composite coating exhibits good antibacterial efficiency with NIR light. • After healing, the composite coating still provides effective protection.