Biomimetic composite gelatin methacryloyl hydrogels for improving survival and osteogenesis of human adipose-derived stem cells in 3D microenvironment

Gelatin methacryloyl (GelMA) hydrogels are used for stem cell encapsulation in bone tissue engineering due to their fast and stable photo-crosslinking. However, cell viability and ability to induce osteogenesis are reduced by reactive oxygen species (ROS) produced during the crosslinking reaction. In this study, we developed biomimetic nanoparticles (TMNs) by combining tannic acid (TA) and simulated body fluid (SBF) minerals, and used them to synthesize GelMA-based composite hydrogels for addressing those limitations. The optimal concentrations of TA and SBF were investigated to create nanoparticles that can effectively scavenge ROS and induce osteogenesis. The incorporation of TMNs into composite hydrogels (G-TMN) significantly enhanced the survival and proliferation of encapsulated human adipose-derived stem cells (hADSCs) by providing resistance to oxidative conditions. In addition, the ions that were released, such as Ca²⁺ and PO₄³⁻, stimulated stem cell differentiation into bone cells. The hADSCs encapsulated in G-TMN had 2.0 ± 0.8-fold greater viability and 1.3 ± 1.8 times greater calcium deposition than those encapsulated in the hydrogel without nanoparticles. Furthermore, the in vivo transplantation of G-TMN into a subcutaneous mouse model demonstrated the rapid degradation of the gel-network while retaining the osteoinductive particles and cells in the transplanted area. The increased cellular activity observed in our multifunctional composite hydrogel can serve as a foundation for novel and effective therapies for bone deformities.