Crab Shell Inspired Chitin/β-Tricalcium Phosphate Screws as Orthopedic Implants

Resorbable fracture fixation materials are currently gaining widespread attention due to their ability to avoid the second surgery and stress shielding. Inspired by the structure of the crab shell, herein, we propose high-strength resorbable screws composed of β-tricalcium phosphate (β-TCP) and chitin as orthopedic implants. The incorporation of β-TCP into the chitin matrix not only improved the mechanical performance of the screws but also endowed them with osteogenic activity. The resulting chitin/β-TCP screws exhibited high flexural strength (up to 297 MPa) and tensile strength (up to 257 MPa), comparable to cortical bone. The chitin/β-TCP screws had favorable biocompatibility in vitro, which effectively promoted the adhesion of BMSCs and the expression of osteogenesis-related genes (RUNX2 and OCN), thereby facilitating bone healing. Importantly, the in vivo assessment of the rat femoral condyle indicated that the chitin/β-TCP screws were firmly fixed within the bone tunnel without inflammatory response and promoted the formation of new bone tissue during degradation. This work provides a biomimetic strategy for designing polysaccharide-based screws with significant potential applications in fracture internal fixation and anterior cruciate ligament reconstruction.