Biodegradable Neo-Bone-Responsive Scaffold Fabricated by Organic–Inorganic Click Fumarate Polymers for Bone Tissue Engineering

Abstract The development of biocompatible and biologically responsive scaffolds remains a key challenge for bone tissue engineering. Here, we report an enzyme-degradable, metal-free click-cross-linked organic–inorganic nanohybrid (Enz-Deg-Click-ON) scaffold with high biocompatibility for bone repair. The formulation was synthesized using a cyclooctyne-functionalized poly(propylene fumarate) polyphosphoester (PPF-poly(PE-BCN)) and azide-terminated dendritic polycaprolactone (PCL) with a polyhedral oligomeric silsesquioxane core (POSS-PCL-N3) via strain-promoted alkyne-azide cycloaddition (SPAAC) bioorthogonal click chemistry. The incorporation of phosphate-containing linkages enabled alkaline phosphatase (ALP)-responsive degradation. The scaffold exhibited rapid catalyst-free crosslinking, tunable swelling, and suitable mechanical properties. In vitro studies demonstrated excellent cytocompatibility, robust stem cell proliferation, and enhanced osteogenic differentiation with an elevated level of ALP and Runx2 expression. Enzyme-triggered degradation was confirmed in the presence of ALP. In the in vivo rat calvarial defect model, the scaffold significantly improved bone regeneration, as shown by an increased bone volume, mineral density, and defect coverage. Histological and immunofluorescence analyses revealed enhanced collagen deposition, angiogenesis, and osteogenesis. These results indicate that the Enz-Deg-Click-ON system provides a dynamic, bioresponsive platform for bone repair.