Abstract: BACKGROUND: Compared with other bone repair materials, electrospun membranes have good cell compatibility and mechanical strength. This series of advantages expands its application potential in drug delivery and tissue engineering. 
OBJECTIVE: To prepare nanohydroxyapatite-polyether carbonate urethane electrospun membranes and evaluate the in vitro and in vivo bioactivity of electrospun membranes.
METHODS: (1) Polyether carbonate urethane and nanohydroxyapatite-polyether carbonate urethane electrospun membranes were prepared by electrospinning machine, and the microscopic morphology and water contact angle of the two electrospun membranes were characterized. Rat bone marrow mesenchymal stem cells were co-cultured with polyether carbonate urethane and nanohydroxyapatite-polyether carbonate urethane electrospun membranes, respectively. Cells cultured alone were used as controls. CCK-8 assay, live-dead staining, skeleton staining and EdU staining were performed respectively. After osteogenic induction, alkaline phosphatase staining and alizarin red staining were performed respectively. (2) Twenty-seven SD rats were randomly divided into three groups. The control group (n=9) constructed a full-thickness skull defect with a diameter of 5 mm and did not receive any treatment. The polyether carbonate urethane group (n=9) and nanohydroxyapatite-polyether carbonate urethane group (n=9) constructed a full-thickness skull defect with a diameter of 5 mm and then implanted polyether carbonate urethane-rat bone marrow mesenchymal stem cell scaffold and nanohydroxyapatite-polyether carbonate urethane-rat bone marrow mesenchymal stem cell scaffold, respectively. Eight weeks after surgery, skull Micro-CT analysis, hematoxylin-eosin staining, and Masson staining were performed, respectively.
RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that both electrospun membranes showed uniform fiber structure and smooth fiber surface, and the nanohydroxyapatite-polyether carbonate urethane electrospun membrane had a larger fiber diameter and more dispersed arrangement. There was no significant difference in the water contact angles of the two electrospun membranes, and both had good hydrophilicity. The results of CCK-8 assay and EdU staining showed that both electrospinning membranes could promote the proliferation of rat bone marrow mesenchymal stem cells, and the promoting effect of nanohydroxyapatite-polyether carbonate urethane electrospinning membrane was more obvious. Live-dead staining and skeleton staining showed that rat bone marrow mesenchymal stem cells had good morphology and high activity on the two electrospinning membranes. The results of alkaline phosphatase and alizarin red staining showed that both electrospinning membranes could promote the osteogenic differentiation of rat bone marrow mesenchymal stem cells, and the promoting effect of nanohydroxyapatite-polyether carbonate urea electrospinning membrane was more obvious. (2) Micro-CT analysis results showed that both electrospinning membranes could promote the repair of rat skull defects, and the promoting effect of nanohydroxyapatite-polyether carbonate urethane electrospinning membrane was more obvious. Hematoxylin-eosin and Masson staining results showed that compared with the control group, more new bone mass was observed in the bone defects of the polyether carbonate urethane group and the nanohydroxyapatite-polyether carbonate urethane group, and the bone repair effect of the nanohydroxyapatite-polyether carbonate urethane group was better. (3) The results show that the nanohydroxyapatite-polyether carbonate urethane electrospinning membrane has good fiber structure and biocompatibility, and can promote the proliferation, osteogenic differentiation, and repair of rat bone marrow mesenchymal stem cells. 

Key words: electrospinning, nanohydroxyapatite, polyether carbonate urethane, bone defect, tissue engineering, biomaterial