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.