Medium-chain triglyceride/water Pickering emulsion stabilized by phosphatidylcholine-kaolinite for encapsulation and controlled release of curcumin

Pickering emulsions have received widespread attention for encapsulating lipophilic guests in the biomedical and food fields. However, control of the stabilities and demulsification of Pickering emulsions to allow the release of encapsulated species remains a challenge in gastrointestinal conditions. In this work, phosphatidylcholine-kaolinite was prepared by modification of natural kaolinite with phosphatidylcholine and was used as an emulsifier to stabilize medium-chain triglyceride (MCT)/water Pickering emulsions for encapsulating curcumin, a natural antioxidant drug. Simulated gastric and intestinal digestion and a cell uptake assay were implemented for the curcumin-loaded MCT/water Pickering emulsion to study its demulsification and the bioavailability of curcumin. The results revealed that the wettability of phosphatidylcholine-kaolinite could be tailored by controlling the modification temperature so that it could control the emulsion stability. The prepared phosphatidylcholine-kaolinite, with a three-phase contact angle of 123°, was an optimal emulsifier for the enhanced stabilization of the MCT/water Pickering emulsion, especially in the presence of gastric acid. The phosphatidylcholine-kaolinite distributed at the water-oil interface and formed a dense shell structure on the surfaces of the emulsion droplets, controlling the demulsification efficiency to release the encapsulated curcumin. Only 18.9% of the curcumin was released in the simulated gastric conditions after 120 min of digestion due to the demulsification of the MCT/water Pickering emulsion, while it was completely released after 150 min of digestion in simulated intestinal conditions, as expected. This Pickering emulsion stabilized by phosphatidylcholine-kaolinite is a promising delivery system for lipophilic foods or drugs to enhance their bioavailability.