Drug-preloadable methacrylated gelatin microspheres fabricated using an aqueous two-phase system

Gelatin microspheres (GMS) can retain biomolecules and be incorporated into artificial tissues and organs for tissue regeneration. However, the inactivation of biomolecules during the conventional fabrication process of GMS requires postloading of biomolecules to prefabricated GMS. Herein, a novel method for fabricating drug-preloaded GMS using a water-in-water (w/w) emulsification technique, is reported. A highly concentrated gelatin methacrylate (Gm) solution containing fibroblast growth factor 2 (FGF2), a model drug, was emulsified in a highly concentrated polyethylene glycol solution, and the mixture was irradiated with ultraviolet light. The obtained water-in-water gelatin methacrylate microspheres (w/w GmMS) were superior to conventional GMS in terms of stability, FGF2-loading efficiency, and sustained release of FGF2. The FGF2-loaded w/w GmMS efficiently activated the proliferation of adipose tissue-derived mesenchymal stem cells (ASCs). In addition, FGF2-loaded w/w GmMS incorporated into multicellular spheroids of ASCs increased the viability of ASCs in the spheroids. The therapeutic efficacy of ASC spheroids in a wound healing mouse model was significantly improved by the incorporation of FGF2-loaded w/w GmMS. These results indicate that drug-preloadable w/w GmMS can be widely applied in tissue engineering and regenerative medicine strategies.