Metallic ions integrated in tannic acid (TA) as a metal–organic-like complex coating on biodegradable magnesium for enhanced corrosion control and biocompatibility

Biodegradable materials such as magnesium and its alloys have significant potential for realizing biomedical advancements; however, their rapid degradation in biological settings restricts their widespread use. A metal–organic-like metallic ion-integrated tannic acid (TA) complex coating was immobilized on the surface of the rare earth element-free Mg–2Zn–1Mn (ZM21) magnesium (Mg) alloy for improving the corrosion resistance. The TA was first immobilized on an Mg substrate, followed by an alternating dip-coating process of Ce ions and TA to build a complex coating. Such immobilization process was executed by the chelation reaction between TA molecules and metallic ion. The EIS results show that after 7 days of immersion in SBF solution, the impedance module value of the Mg–TA/Ce coating at 0.01 Hz still remains at 10⁴ Ω cm², and its tensile strength decreased by 2.1%, demonstrating its excellent corrosion resistance. This metal–organic coating also induces the proliferation of osteoblast and fibroblasts cells. This metal–organic complex coating can serve as a viable means for modifying magnesium-based orthopedic implants.