Smart Implantable Hydrogel for Large Segmental Bone Regeneration

Large segmental bone defects often lead to nonunion and dysfunction, posing a significant challenge for clinicians. Inspired by the intrinsic bone defect repair logic of "vascularization and then osteogenesis", this study originally reports a smart implantable hydrogel (PDS-DC) with high mechanical properties, controllable scaffold degradation, and timing drug release that can proactively match different bone healing cycles to efficiently promote bone regeneration. The main scaffold of PDS-DC consists of polyacrylamide, polydopamine, and silk fibroin, which endows it with superior interfacial adhesion, structural toughness, and mechanical stiffness. In particular, the adjustment of scaffold cross-linking agent mixing ratio can effectively regulate the in vivo degradation rate of PDS-DC and intelligently satisfy the requirements of different bone defect healing cycles. Ultimately, PDS hydrogel loaded with free desferrioxamine (DFO) and CaCO₃ mineralized ZIF-90 loaded bone morphogenetic protein-2 (BMP-2) to stimulate efficient angiogenesis and osteogenesis. Notably, DFO is released rapidly by free diffusion, whereas BMP-2 is released slowly by pH-dependent layer-by-layer disintegration, resulting in a significant difference in release time, thus matching the intrinsic logic of bone defect repair. In vivo and in vitro results confirm that PDS-DC can effectively realize high-quality bone generation and intelligently regulate to adapt to different demands of bone defects.