Food-grade filled hydrogels for oral delivery of lipophilic active ingredients: Temperature-triggered release microgels

Delivery systems are often needed to encapsulate lipophilic active agents, protect them during storage, and then release them within the mouth. In this study, gelatin and caseinate were used to fabricate temperature-sensitive filled hydrogel particles. Filled hydrogel microspheres were formed by electrostatic complexation of caseinate and gelatin in the presence of caseinate-coated lipid droplets. This was achieved by mixing aqueous 1% sodium caseinate and 1% gelatin solutions (volume ratio 1:2) at pH 5.8 with an oil-in-water emulsion. The majority of lipid droplets were trapped within the hydrogel microspheres. Turbidity and viscosity measurements of the hydrogels indicated that hydrogel particles dissociated upon heating because of gelatin melting (around 35 °C). Light scattering and confocal fluorescence microscopy indicated that lipid droplets were released from the gelatin-based hydrogel particles after oral processing, which was attributed to hydrogel melting under simulated mouth conditions. Our results suggest that hydrogel particles based on electrostatic complexation of sodium caseinate and gelatin could be useful as oral delivery systems for lipophilic active agents.