Injectable P24–Si-CaP/GelMA composite hydrogel for repairing bone defects

The repair of severe bone defects remains a major clinical challenge. While our team has developed a Si-CaP material with significant potential for bone defect repair, its limitations in application convenience and poor degradability have hindered practical use. This study addresses these issues by creating an injectable light-curable P24-Si-CaP/GelMA (P-Si/G) composite hydrogel, further enhancing Si-CaP's osteogenic capacity through P24 peptide grafting. The composite material integrates P24-Si-CaP bio-ceramic powder (with surface-modified osteogenic peptide) into a GelMA hydrogel matrix. Experimental results demonstrate that when the Si-CaP/GelMA mass ratio is 20%, the hydrogel exhibits optimal gel-forming capability, mimics the inorganic/organic ratio of natural bone, and maintains excellent mechanical strength. Comprehensive characterization confirmed successful peptide conjugation, resulting in superior porosity and enhanced hydrophilicity. <i>In vitro</i> experiments showed that P-Si/G hydrogel significantly promotes the migration and osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs), evidenced by increased alkaline phosphatase activity, mineralization, and enhanced expression of osteogenic genes, with no observed cytotoxicity. In a rat cranial defect model, micro-CT and histological analysis revealed that the P-Si/G hydrogel group achieved significantly higher new bone formation and near-complete defect closure after 8 weeks of implantation compared to control, pure GelMA, and Si-CaP/GelMA groups, demonstrating <i>in vivo</i> safety. Comprehensive research demonstrates that the P24-Si-CaP/GelMA composite hydrogel exhibits outstanding biocompatibility, osteogenic induction, and bone-conducting properties, making it a highly promising injectable scaffold material for bone tissue engineering.