Characterization of an Injectable Poly(vinyl alcohol)-gelatin Hydrogel for Growth Factor Delivery in an Orthopedic Application

Injectable hydrogels have attracted considerable interest because of their minimally invasive delivery and adaptability to patient-specific defects. This study aimed to investigate the suitability of a photo-crosslinkable tyraminated poly(vinyl alcohol)-gelatin (PVA-GT) polymer network as an injectable platform for tissue engineering and growth factor delivery. Two formulations were developed by varying the concentration of ruthenium/sodium persulfate (Ru/SPS), resulting in formulation-specific physical properties with fast (18 days) and slow (36 days) degradation rates. Their injectability was confirmed across a range of needle sizes (14 to 22G), ensuring versatility for multiple applications. Cytokine release from peripheral blood mononuclear cells and THP-1 demonstrated no inflammatory response due to residual ruthenium. When injected subcutaneously into a mouse model, the fast-degrading formulation exhibited greater cellular and vascular infiltration compared to the slow-degrading one. By leveraging bi-phenol bond formation within the polymer network, the fast-degrading injectable hydrogels were used as a growth factor delivery platform for bone morphogenetic protein-2 (BMP-2). BMP-2-loaded hydrogels were injected into the femoral head of a Legg-Calvé-Perthes disease swine model, preventing the necrosis progression and improving piglets' mobility relative to the sham. These findings highlight the potential of injectable PVA-GT hydrogels as tunable platforms for regenerative therapies, with implications for personalized orthopedic treatments.