Injectable PEGDA/nano-hydroxyapatite composite hydrogel for minimally invasive bone regeneration

Abstract Engineering bioactive polymer composites with injectability and controlled in situ curing presents an effective strategy for minimally invasive bone regeneration. This study reports the development and characterization of a PEGDA/nano-hydroxyapatite (nHAp) composite hydrogel engineered for redox-initiated in situ curing and tunable injectability. The integration of nHAp within the PEGDA matrix creates a biomimetic environment that supports cellular infiltration and mineralization, while its injectable nature allows precise defect filling with minimal surgical intervention. In vitro evaluation demonstrated that gelation, swelling, and structural stability were strongly influenced by nHAp loading. Increasing nHAp content reduced water uptake and improved mechanical integrity, likely through enhanced crosslinking density. Among the tested formulations, hydrogels containing 5% PEGDA and 7.5% nHAp with minimal initiator concentration exhibited the most favourable properties, combining controlled swelling, slower degradation, and mechanical robustness. Cytocompatibility assessed using MTT assay on L929 fibroblasts confirmed that the 7.5% nHAp formulation maintained higher metabolic activity compared to higher loadings, indicating good biocompatibility. Overall, these findings establish PEGDA/nHAp hydrogels as promising injectable platforms for bone defect repair. By offering osteoconductivity, biocompatibility, and stability, this system shows potential for clinical translation in orthopaedic, craniofacial, and spinal applications requiring minimally invasive regenerative solutions.