Enhanced corrosion resistance, antibacterial properties and osteogenesis by Cu ion optimized MgAl-layered double hydroxide on Mg alloy

Magnesium (Mg) and its alloys have similar densities and elastic moduli to natural bone, making them an excellent choice for orthopedic implants. However, Mg alloys are prone to electrochemical corrosion, which often leads to implant failure and hinders the further development of Mg alloys due to bacterial infection around the implant. This work aims to enhance the corrosion resistance of Mg alloys, and provide theoretical guidance for solving the problem that Mg-based orthopedic implants are susceptible to bacterial infection and, thus, implant failure. In order to solve the corrosion problem, the Mg alloy AZ91D was used as the substrate, and a compact and uniform MgAlCu-layered double hydroxide (Mg(Cu)-LDH) was prepared on its surface using a hydrothermal method. The Mg(Cu)-LDH provides a barrier between the AZ91D and corrosive liquid, which effectively protects the Mg substrate from being corroded. The Mg(Cu)-LDH shows great cell viability for MC3T3-E1 cells. The Cu²⁺ and Mg²⁺ in the coating also endow the Mg(Cu)-LDH/AZ91D with antibacterial properties, showing strong antibacterial effects on both E. coli and S. aureus with antibacterial rates over 85%. Finally, in vivo results indicated that a LDH-coated implant had no systemic effects on the hearts, livers, spleens, lungs or kidneys. It was shown that 4 weeks after surgery the ratio of bone volume to tissue volume (BV/TV) of the LDH implant was 24%, which was 1.7 times that observed for AZ91D.