▎ 摘　　要

Improving the degradation rate and bioactivity of magnesium in physiological environment is helpful to its application in biomedical field. Alloying treatment and surface modification are two effective ways. In the present study, a novel surface modification strategy, i.e. hydroxyapatite/graphene oxide/magnesium hydroxide (HA/GO/Mg(OH)(2)) composite coating constructed on the surface of magnesium-calcium alloy by the combination of hydrothermal treatment, electrophoretic deposition and electrochemical deposition, were proposed for magnesium-calcium alloy (ZQ). Scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis confirm that the surface of the coating sample (ZQ-HEP) is composed of outer nano-sheet HA, middle flocculent-lamellae GO and inner Mg(OH)(2) nano-sheet. The electrochemical corrosion resistance test in vitro shows that compared with the untreated ZQ, ZQ-HEP has higher corrosion resistance in phosphate buffer solution (PBS). A rabbit femoral condyle fracture model was constructed to evaluate the fracture repair effect of ZQ samples before and after surface modification. Postoperative gross observation, radiograph and histological analysis confirm that compared with the untreated ZQ, ZQ-HEP screws could decrease the hydrogen release obviously and thus the subcutaneous emphysema after implantation into the body. Meanwhile, due to its higher corrosion resistance and bioactivity, ZQ-HEP screw could maintain its integrity better than the ZQ one at 4 weeks postoperatively, and induce more new bone growth. Therefore, more rapid fracture healing is observed on ZQ-HEP than ZQ. In conclusion, the multi-functional coating construction strategy proposed in current study could have good prospect of clinical application. It can not only regulate the degradation rate of medical magnesium metals, but also significantly improve their osteogenic ability.