Development of High-Performance Chitosan-Silk Fibroin Hydrogels in Bone Repair: Mechanical and Biological Enhancements

Bone tissue engineering has attracted increasing interest, with natural polymers being explored for bone repair. However, most natural polymers lack sufficient mechanical strength for clinical application. In this study, methacrylated chitosan (CSMA) and silk fibroin (SF) were utilized as matrix components to develop an interpenetrating polymer network. To enhance the stability of the composite hydrogel, silk nanofibrils (SNFs) and amorphous calcium phosphate (ACP) were added as reinforcing phases. Using this system, bone screws and plates were fabricated. Results showed that the incorporation of SNF significantly improved the mechanical properties of the hydrogel, increasing its fracture strength from 86 kPa to 212 kPa, representing a 146% enhancement. Additionally, the stiffness and toughness of the material were improved to approximately 386% and 65%, respectively. Moreover, the incorporation of ACP enhanced the structural stability of the hydrogel and promoted the adhesion and proliferation of osteoblasts. The manufactured bone screws and plates displayed fracture strengths of 38.1 MPa and 57.8 MPa, with moduli of 805.9 MPa and 3.15 GPa, respectively. In vitro degradation studies of the bone screws revealed moderate degradation rate and favorable structure stability. The composite material demonstrated high effectiveness in promoting osteogenic differentiation of bone marrow mesenchymal stem cells and exhibited good osteoblast compatibility. The developed CSMA/SF/SNF/ACP composite material exhibits considerable mechanical and bioactive properties, providing new insights for the design of bone repair materials and presenting significant potential for biomedical applications.