Sustained release of Semaphorin 3A from a-tricalcium phosphate based cement composite contributes to osteoblastic differentiation of MC3T3-E1 cells

The reinforcement of calcium phosphate materials with silk fibroin （SF） has been one of the strategies to overcome the brittleness. However, the lack of osteoinductivity may still restrict their further use. This study aimed to investigate the biocompatibility and osteogenesis capacity of a novel Semaphorin 3A-loaded chitosan microspheres/SF/a-tricalcium phosphate composite （Sema3A CMs/SF/a-TCP） in vitro. Sema3A was first incorporated into CMs, and the Sema3A CMs/SF/a-TCP composite was then prepared. The morphology of the CMs was observed using SEM. The in vitro release kinetics, cytotoxicity, and cell compatibility were evaluated, and the real-time quantitative polymerase chain reaction （RT-qPCR） and activity of alkaline phosphatase （ALP） were used to evaluate the osteogenesis capacity of the composite. The in vitro release of Sema3A from the Sema3A CMs/SF/a-TCP composite showed a temporally controlled manner. The extract of the Sema3A CMs/SF/a-TCP composite presented no obvious side effect on the MC3T3-E1 cell proliferation, nor promote cell proliferation. The MC3T3-E1 cells were well-spread and presented an elongated shape on the Sema3A CMs/SF/a-TCP composite surface; the ALP activity and the osteogenic-related gene expression were higher than those seeded on the surface of the CMs/SF/a-TCP and SF/a-TCP composites. In conclusion, Sema3A CMslSF/a-TCP has excellent biocompatibility and contributes to the osteoblastic differentiation of MC3T3-E1 cells.