Multifunctional nanocomposite hydrogel with dual-factor controlled release for stem cell recruitment, immunomodulation and bone remodeling.

Bone regeneration is a dynamic, multistage process requiring the orchestrated interplay of cellular recruitment, immune modulation, and balanced osteoblast-osteoclast activity. To address this clinical challenge, we developed a nanocomposite hydrogel-based drug delivery system integrating gelatin methacrylate (GelMA) and silk fibroin methacrylate (SFMA) scaffolds containing mesoporous silica nanoparticles (MSNs) for spatiotemporally controlled co-delivery of stromal cell-derived factor-1α (SDF-1α) and osteoprotegerin (OPG). This dual-delivery platform enabled sustained and localized release of immunoregulatory and osteoprotective agents, achieving a synchronized modulation of the regenerative microenvironment. The MSNs functioned as an effective nanocarrier to preserve bioactivity and prolong release kinetics of bioactive factors, while the hydrogel matrix provided structural integrity and protease-responsive degradation matching bone repair dynamics. The system potentiated bone marrow mesenchymal stem cell (BMSC) recruitment, proliferation, and osteogenic differentiation, reprogrammed macrophage polarization toward a pro-regenerative M2 phenotype, and suppressed osteoclastogenesis. In vivo validation using a rat critical-sized femoral defect model revealed accelerated osseous regeneration. Mechanistically, transcriptomic profiling identified concerted PI3K/Akt-MAPK pathway activation. The immunomodulatory hydrogel reduced pro-inflammatory cytokines while elevating osteogenic factors. Crucially, the hydrogel restored osteoblast-osteoclast crosstalk balance, suppressing TRAP osteoclast formation through OPG-mediated RANKL inhibition. Overall, this hydrogel-based delivery platform demonstrates a clinically translatable strategy for drug-enabled bone regeneration, with precise control over therapeutic release, spatial localization, and immuno-osteogenic coupling.