Biomimetic management of bone healing stages: MOFs induce tunable degradability and enhanced angiogenesis-osteogenesis coupling

Currently, biodegradable biomaterials are extensively used in bone regeneration. Nevertheless, a significant challenge remains in accurately adjusting their degradation rates to match bone healing stages to achieve bone regeneration. Herein, we present a novel biodegradable bone grafts integrated with zeolite imidazole framework-8 (ZIF-8) nanocrystals, fabricated via microinjection molding. Apart from the reinforcing effect derived from the in-situ fibrillation of PCL in PLGA, nanoscale ZIF-8 is inspiringly demonstrated to control the PLGA degradation. Both molecular dynamic simulation and experimental results indicate that Zn2+ derived from ZIF-8 nanocrystals acts as a Lewis acid to participate the degradation of PLGA matrix, thus successfully reconciles the contradiction between degradation of matrix and maintenance of reinforcing phase. Moreover, nanometric ZIF-8 modified bone grafts improve the angiogenesis-osteogenesis coupling. In vitro, it directly boosts HIF-1α and capillary-like network formation of endothelial cells (ECs), and RUNX2 and OCN expression in bone marrow mesenchymal stem cells (BMSCs). In vivo, bone grafts with a moderate concentration (0.5 %) of ZIF-8 nanoparticles aid vascularized bone regeneration by tunable biodegradation matching bone healing stages. Further, RNA sequencing shows PLGA/PCL@nZ bone grafts promote angiogenesis-osteogenesis by cooperatively regulating calcium signaling pathway in both ECs and BMSCs. Collectively, this study delineates a groundbreaking bone repair strategy with profound clinical application potential.