Nanostructured Hydroxyapatite Coating for Biodegradability Improvement of Magnesium-based Alloy Implant

Due to particular requirement for implant prostheses to mechanical stability and biocompatibility for regeneration of hard tissues injuries, bioresorbable metallic implants have attracted special place in orthopedics in recent years because of excluding secondary surgery for extracting them. While magnesium is one of the most vital elements in body metabolism and revival of harmed bones, its corrosion rate in chloride solutions such as human body fluid is too high and this matter would have unpleasant consequences as a supporting implant. In this study, a magnesium-based alloy (AZ91) was used as a substrate and coated with nanostructured hydroxyapatite (n-HA) via a sol–gel method in order to achieve releasing Mg²⁺ ions gradually which assists osteoblast cells to regenerate injured bones. Potentiodynamic plots revealed that the corrosion resistance behavior of the coated substrates had been increased significantly comparing with uncoated specimens. Also, in vitro immersion test evaluation in simulated body fluid solution at 37 ± 1°C within 28 days of immersion discovered significant decrease in evolved gas for n-HA coated against bare AZ91 specimens which indicated that n-HA coating has been considerably successful in developing the controlled barricade of Mg²⁺ ion releasing and indicated that the n-HA coating could decrease the substrate degradation rate to half versus bare substrate.