Abstract: Objective To evaluate the possibility of GO/ZnO/nHAp composite microspheres as bone regeneration materials, a critical bone defect model of the rabbit femoral condyle was established to access bone regeneration in vivo. Methods Composite microspheres were prepared by the ionic gel-drip method, and the prepared GO/ZnO microspheres, nHAp microspheres, and GO/ZnO/nHAp microspheres were implanted into three groups of experimental rabbit femoral condyle standard critical bone defect models, with a blank control group. The animals were killed in batches at 4 weeks, 8 weeks, and 12 weeks after the operation, and the samples were taken completely for evaluation. Gross observation, X-ray film, CBCT detection, qPCR, Western blot, hard histological section, and HE staining of liver and kidney pathology were carried out to explore the osteogenesis and osseointegration of implanted materials. Results At 4 weeks, 8 weeks and 12 weeks after operation, the results of X-ray, CBCT, qPCR and Western blot in the GO/ZnO/nHAp composite microsphere group were significantly better than those in GO/ZnO and nHAp microspheres group at the same time point. The comparison of the experimental results of the qPCR, Western blot and hard tissue section showed that there were statistically significant differences among the three microspheres in promoting bone formation (P<0.05). Conclusion GO/ZnO, nHAp, and GO/ZnO/nHAp all have good biocompatibility and osteogenic activity. GO/ZnO/nHAp composite microspheres can effectively repair the bone defect of rabbit femoral condyle, and their in vivo bone conduction and bone induction properties are superior to GO/ZnO microspheres and nHAp microspheres, which have potential application value in bone defect repair materials.

Key words: Bone regeneration materials, Composite microspheres, Osteoinduction, Critical size defect