Abstract: BACKGROUND: In recent years, alginate hydrogels have been widely used in bone tissue engineering to promote bone regeneration. Studies have shown that deferoxamine can promote angiogenesis and bone regeneration.
OBJECTIVE: To construct strontium alginate/deferoxamine hydrogels and analyze their ability to promote angiogenesis and bone regeneration. 
METHODS: (1) Strontium alginate hydrogels and strontium alginate/deferoxamine hydrogels were prepared by chemical cross-linking method, and the microscopic morphology of the hydrogels was observed by scanning electron microscopy. Strontium alginate hydrogels and strontium alginate/deferoxamine hydrogels were co-cultured with rat bone marrow mesenchymal stem cells. The cytotoxicity of the hydrogels was evaluated by live-dead cell staining and CCK-8 assay. The two hydrogels were cultured with rat bone marrow mesenchymal stem cells for osteogenic induction. The osteogenic differentiation was analyzed by alkaline phosphatase staining, alizarin red staining, and osteopontin immunofluorescence staining. The two hydrogel extracts were co-cultured with human umbilical vein cells, and the angiogenesis was analyzed by tubule formation experiment and CD31 immunofluorescence staining. (2) A 5-mm circular bone defect was made in the skull of 18 SD rats. The rats were randomly divided into three groups, with 6 rats in each group. The control group did not receive any intervention. The other two groups were injected with strontium alginate hydrogel and strontium alginate/deferoxamine hydrogel, respectively. Eight weeks after surgery, the bone repair was analyzed by Micro-CT detection and hematoxylin-eosin and Masson staining.
RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that both hydrogels had a loose and porous structure. Live and dead cell staining and CCK-8 assay showed that the two hydrogels had no cytotoxicity. Alkaline phosphatase staining, alizarin red staining, and osteopontin immunofluorescence staining analysis showed that both hydrogels could promote the osteogenic differentiation of bone marrow mesenchymal stem cells. Tubule formation experiment and CD31 immunofluorescence staining analysis showed that compared with strontium alginate hydrogel, strontium alginate/deferoxamine hydrogel could promote angiogenesis. (2) Micro-CT detection of rat skull defect experiment showed that the new bone formation in the strontium alginate/deferoxamine group was significantly higher than that in the control group and the strontium alginate group. Hematoxylin-eosin and Masson staining showed that the new bone formation and collagen deposition in the strontium alginate/deferoxamine group were significantly better than those in the control group and the strontium alginate group. (3) The results confirm that the strontium alginate/deferoxamine hydrogel has good ability to promote angiogenesis and bone regeneration.

Key words: strontium alginate, hydrogel, deferoxamine, bone injury repair, bone regeneration, engineered bone material