Multifunctional Bioactive Scaffold Facilitating BMSCs-Driven Osteogenesis and Vascularization in Critical-Sized Bone Defect Repair.

Critical-sized bone defects (CSD) remain a major clinical challenge due to three interrelated barriers: inadequate mechanical support, insufficient osteogenic induction, and impaired angiogenesis, all of which hinder effective regeneration. To tackle these, we developed a dual-network bioactive scaffold, ermd bFGF@CB-gel, based on a chondroitin sulfate methacryloyl/bacterial cellulose gel (CB-gel) which synergistically combines three key properties: i) a photocurable biomimetic mineralized scaffold (CB-gel) for in situ bone repair with mechanical support and a bone-ECM-mimicking microenvironment for delivering bone marrow mesenchymal stem cells (BMSCs); ii) a bio-nano carrier (BC) for sustained release of bFGF which enhances the adhesion and proliferation via EGFL/Itga2b pathway, strengthens osteogenic differentiation and mineralization by activating the COMP/PI3K/AKT pathway of rat BMSCs; iii) bFGF released by the dual-network promotes migration and angiogenesis of microvascular endothelial cells by combining FGFR to activate the PI3K/AKT/eNOS pathway. In a rat CSD model, the bFGF@CB-gel achieved a statistically significant increase in new bone volume, as quantified by micro-CT, and enhanced vascular density, evaluated via immunohistochemical staining. These findings highlight the potential of bFGF@CB-gel as an effective local delivery system of BMSCs via linking biomechanics, molecular signaling, and cellular activity, which moves beyond simplistic function stacking to a rational, synergistic design for bone regeneration in CSD, addressing key challenges in reconstructive surgery.