PDA@ZIF-8/LDH composite coating prepared on the Mg-Zn-Ca alloy by one-step hydrothermal method: Characterization, corrosion resistance and in vitro photothermal antibacterial properties

A one-step hydrothermal method was used to deposit a in situ composite coating on a magnesium alloy by adding ZIF-8 nanoparticles modified by polydopamine (PDA) (PDA@ZIF-8) as a photoabsorbing agent and growing Mg-Al double-layer hydroxide (LDH). The results showed that PDA@ZIF-8 nanoparticles had significant influence on the corrosion resistance, antibacterial properties, and biocompatibility of the LDH coating, and improved the compactness and crystallinity of LDH by regulating the growth of its lamella. Compared with the LDH coating, the corrosion current density of the composite coating by adding PDA@ZIF-8 nanoparticles was reduced from 2.28×10 -5 to 1.86×10 −6 A·cm -2 . And its immersion corrosion rates were 0.89 ± 0.05   mm·year −1 in SBF solution for 8 days. Meanwhile, it had antibacterial efficacy of 99.99% and 99.99% against Escherichia coli and Staphylococcus aureus , respectively, with the in vitro photothermal conversion efficiency of 29.77%. Moreover, besides greatly improving osteogenic activity and biocompatibility in vitro, the composite coating with the addtion of PDA@ZIF-8 nanoparticlescan also drive M1-type macrophages to M2-biased phenotypes after exposure to 808   nm NIR light, changing in macrophage secretion for tissue regeneration, and fulfill the excellent antibacterial properties in vivo antibacterial implantation test. This method can provide an effective way and strategy for regulating and enhancing the antibacterial functionalization and improving the corrosion resistance of the double-layer hydroxide coating on the surface of magnesium alloys.