Development of food-grade filled hydrogels for oral delivery of lipophilic active ingredients: pH-triggered release

For certain applications in the food, personal care, and pharmaceutical industries there is a need for oral delivery systems for lipophilic active agents, such as oil-soluble flavors, antimicrobials, nutraceuticals, or drugs. Hydrogel particles fabricated from food-grade biopolymers can be used to develop this type of oral delivery system. In this study, hydrogel particles were fabricated by electrostatic complexation of a protein (casein) and an anionic polysaccharide (alginate). Relatively small hydrogel particles were formed at pH values just above the isoelectric point of the protein (where both biopolymers are negative) using 1% fat, 0.33% casein, and 1.33% alginate, which was attributed to electrostatic attraction between anionic groups on alginate and cationic groups on casein. The hydrogel particles remained intact from pH 4 to 5 but aggregated or dissociated at lower or higher pH values, respectively. Light scattering and confocal fluorescence microscopy indicated that lipid droplets encapsulated within the hydrogel particles were released under simulated oral conditions, which was triggered by a pH change. Our results suggest that hydrogel particles based on electrostatic complexation of casein and alginate may be useful for oral delivery of lipophilic active agents.