Multifunctional hydroxyapatite/tea polyphenol composite coatings on magnesium alloy surfaces for enhancing corrosion resistance and antibacterial properties

The deposition of hydroxyapatite coatings on the surface of magnesium alloys has proven to be an effective option for efficiently reducing their corrosion resistance and increasing their bioactivity. However, the challenge of implant-associated infections due to inadequate antimicrobial properties remains. In this work, a hydroxyapatite/tea polyphenol (HA/TP) composite coating was prepared on a magnesium alloy (AZ31B) substrate by a one-step hydrothermal method. The aim was to retard the corrosion rate of the magnesium alloy while synergistically combining the bioactivity of HA with the antimicrobial properties of TP to realize the multifunctionality of the material. The optimum reaction conditions for the precursor solution at pH 8.5 were determined by the morphology of the coating surface and the crystallographic phase analysis. Fourier transform infrared spectroscopy analysis experiments showed that chemical bonds were formed between HA and TP, which improved the stability of the structure. Antimicrobial experiments showed that the addition of TP exhibited broad-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus . Electrochemical experiments showed that the HA/TP coating reduced the corrosion rate of magnesium alloys to 0.349 mm/y. In addition, the coating exhibited excellent biocompatibility, promoted the proliferation of MC3T3-E1 osteoblasts and had the ability to rapidly induce mimetic mineralization. This study presents a novel strategy for the preparation of multifunctional coatings with both corrosion resistance, osteogenic activity and antimicrobial properties, providing a potential solution for degradable magnesium-based bone implants.