Electrodeposited dopamine/strontium-doped hydroxyapatite composite coating on pure zinc for anti-corrosion, antimicrobial and osteogenesis.

Zinc-based biometal is expected to become a new generation of biodegradable implants. Due to its antibacterial and biocompatibility in vivo, zinc metals is recently considered to be the most promising biodegradable metal, However, cytotoxicity is the thorny problem that currently restrict its application, due to the excessive Zn ions released during degradation. In order to solve these problems, dopamine modified strontium-doped hydroxyapatite coating (SrHA/PDA) was fabricated on alkali-treated pure zinc to improve its corrosion rate and cytocompatibility by electrodeposition for the first time. The obtained coating showed a dense structure and high crystallinity, which was attributed to the attraction of Ca ions by polydopamine. The results showed that the SrHA/PDA coating delayedthe degradation rate of zinc metal, which reduced the release of Zn, thereby reducing its cytotoxicity. Additionally, electrochemical tests showed that SrHA/PDA coating can reduce the corrosion rate of pure zinc. In vitro cell viability showed that even at high Zn concentrations (3.11 mg/L), preosteoblasts (MC3T3-E1) cells proliferated at a high rate on SrHA/PDA, thus confirming that Sr counteracted the cytotoxic effects of Zn and promoted cell differentiation. Moreover, the SrHA/PDA coating still maintained excellent antibacterial effects against pathogenic bacterial strains (Escherichia coli and Staphylococcus aureus). Mild pH changes had no significant effect on the viability of cells and bacterias. Collectively, the present study elucidated that by coating SrHA/PDA/Zn(OH) on Zn, a controllable corrosion rate, original antibacterial properties and better cell compatibility can be achieved. This provided a new strategy for the surface modification of biodegradable Zn.