In vivo comparative property study of the bioactivity of coated Mg–3Zn–0.8Zr alloy

• Microstructure of uncoated, Ca–P and MgF2 coated Mg–3Zn–0.8Zr implants were analyzed.
• The degradation, evolution and biocompatibility for implants were tested and analyzed.
• New bone formation was further analyzed by using micro-computed tomography.
• MgF2 coating is a potential candidate for biodegradable magnesium implant materials.

In this in vivo study, degradable Mg–3Zn–0.8Zr cylinders were coated with a calcium phosphorus compound (Ca–P) layer or a magnesium fluoride (MgF2) layer; uncoated Mg–3Zn–0.8Zr alloy was used as a control. These were then implanted intramedullary into the femora of nine Japanese big-ear white rabbits for implantation periods of 1, 2 and 3 months. During the postoperative observation period with radiographic examination, the results showed that the MgF2-coated implants were tolerated well compared to the Ca–P-coated implants and uncoated implants. Moreover, large amounts of cells, rich fibrillar collagen and calcium and phosphorus products were found on the surface of the MgF2-coated implants using scanning electron microscopy. Micro-computed tomography further showed a slight decrease in volume (23.85%) and a greater increase in new bone mass (new bone volume fraction = 11.56%, tissue mineral density = 248.81 mg/cm3) for the MgF2-coated implants in comparison to uncoated and Ca–P compound-coated implants after 3 months of implantation.