Functionalization of Photocrosslinkable GelMA Hydrogel With Metal Oxides for Direct Pulp Capping

In this study, a photocrosslinkable methacrylated gelatin (GelMA) hydrogel, functionalized with metal oxide nanoparticles, was developed to support dentin regeneration in direct pulp capping applications. Magnesium (MgO), silicon (SiO₂), strontium (SrO), and zinc (ZnO) were incorporated into GelMA at concentrations of 0.1%, 0.2%, 0.3%, 0.5%, and 1% (v/v) to assess cytotoxicity in human stem cells from the apical papilla (SCAPs). Based on the results, MgO, SiO₂, and SrO were selected for further functionalization of GelMA at reduced concentrations (0.1%, 0.075%, 0.05%, and 0.025%; v/v) to evaluate the odontogenic potential of the formulations. Physicochemical analyses were performed to characterize the biomaterials. ZnO exhibited cytotoxicity at all tested concentrations. In contrast, the other oxides demonstrated excellent bioactivity and enhanced cell proliferation, except for SrO 0.025%. A significant increase in alkaline phosphatase (ALP) activity and mineralized matrix deposition was observed across all groups, with the most pronounced effects seen in MgO 0.05%, MgO 0.025%, and SrO 0.075%. The functionalized hydrogels exhibited a porous microstructure with a slow and controlled release of oxide-derived species over 14 days. FTIR analysis confirmed the complexation of Mg²⁺, Si⁴⁺, and Sr²⁺ ions within the GelMA structure. In conclusion, our results demonstrate that GelMA functionalized with MgO 0.05%, SiO₂, and SrO 0.075% enhances odontoblastic differentiation and promotes reparative mineralized matrix deposition under osteogenic conditions, favoring reparative dentinogenesis. These findings highlight the promising potential of this biomaterial for future applications in direct pulp capping procedures.