3D Bioprinting of Giant Salamander Mucin-Based Bioink for Enhanced Bone Regeneration

There is an urgent need to overcome the limitations associated with limited autologous bone availability, allogeneic bone rejection, and the insufficient bioactivity of traditional materials for bone-defect repair. In this study, skin secretions from Andrias davidianus (SSAD) were compounded with methacrylated gelatin (GelMA) to develop a novel bioink and construct bone-regeneration scaffolds loaded with osteoblasts via extrusion-based 3D bioprinting. The optimized GelMA/SSAD bioink (50% v/v SSAD, 6% w/v GelMA) demonstrated excellent printability characterized by shear-thinning behavior and high-resolution structure formation and significantly enhanced mechanical strength. In vitro studies demonstrated that the scaffolds were not only biocompatible but also effective in promoting osteoblast proliferation, differentiation, and mineralization, as evidenced by significantly increased ALP activity and the upregulated expression of key osteogenic genes (RUNX2 and OCN). In a rat cranial bone defect model, the new bone volume fraction of the GelMA/SSAD scaffolds (12.54%) was markedly higher than that of the pure GelMA control group (9.82%) eight weeks after implantation. Multimodal analyses revealed that the scaffold synergistically accelerated bone regeneration by promoting TRAP-positive osteoclast activity and increasing type III collagen deposition. Overall, this SSAD-based bioink combines excellent printability, biocompatibility, and strong osteogenic activity, thereby providing a promising strategy for functional bone repair.