Optimization of a Gelatin–Potassium Phosphate Aqueous Two-Phase System for the Preparation of Hydrogel Microspheres

An aqueous two-phase system provides a simple route toward the preparation of gelatin emulsions. Here, we present a simple method to generate water-in-water (w/w) emulsions from an aqueous two-phase system: gelatin and potassium phosphate (K2HPO4) salt. Liquid gelatin forms as the dispersed phase of the two-phase emulsion system, and gelatin microspheres can be retrieved after a visible light-induced crosslinking reaction. We investigated the effect of the continuous phase volume ratio on the formation of the phase-separation and emulsification process. We also studied the influence of the polymerization method on the size and morphology of gelatin hydrogel particles. The results demonstrated that K2HPO4 is an appropriate phase-forming salt, where biodegradable gelatin particles obtained through this w/w emulsion system have potential for biomedical applications. In addition, sustained release of a model molecule, methylene blue, was observed for up to 5 days from gelatin particles. This system is advantageous because if provides an inexpensive emulsion platform that avoids the use of organic solvents or auxiliary polymers to form a continuous phase.