Evaluation of Microstructural Features and in Vitro Biocompatibility of Hydrothermally Coated Fluorohydroxyapatite on AZ80 Mg Alloy

Mg-based alloys as biodegradable materials have several advantages. However, the extensive applications of Mg-based alloys are limited mainly by their high corrosion rate and loss in structural integrity in a physiological environment. In order to improve the corrosion resistance and biocompatibility of biomedical magnesium, fluorine (F) ions are doped in hydroxyapatite (HA) to form fluorohydroxyapatite (FHA) surface coatings on the Mg-8.5Al-0.5Zn (AZ80) Mg alloy by the hydrothermal synthesizing process. Experimental evidence confirmed that FHA coatings with nanoscaled needle-like crystals can be uniformly deposited without rupture on the entire surface of AZ80 Mg alloy by the hydrothermal synthesizing process. The hydrothermal deposition coating on AZ80 is composed of a Mg(OH)₂ intermediate layer and a FHA top coat. X-ray photoelectron spectroscopy results show that fluorine ions are successfully substituted into the HA crystal structure. Potentiodynamic polarization and immersion tests in the Kokubo's simulated body fluid (SBF) show that the corrosion resistance of AZ80 is significantly improved and the dissolution rate is decreased with the deposition of hydrothermal FHA coatings. The in vitro cell culture studies, using human osteosarcoma MG63 osteoblast-like cell, demonstrated that significant cell viability and proliferation on the surface of FHA-coated AZ80 Mg alloy after 6 to 48 h cell culture. The results suggest that the hydrothermally synthesized FHA coating is effective to improve the in vitro biocompatibility of the Mg-based alloys.