Fabrication of epigallocatechin-3-gallate nanocarrier based on glycosylated casein: stability and interaction mechanism.

Polyphenols normally have strong binding affinity with proteins, which may lead to protein precipitation. Glycosylation of protein via Maillard reaction in mild condition may inhibit the precipitation. This study prepared nanocomplexes of epigallocatechin-3-gallate (EGCG) and protein, and their stability against environmental stress was investigated. Subsequently, these findings were correlated with the interactions between EGCG and casein. Results showed that glycosylated casein displayed strong encapsulating and retaining capacity to EGCG, and no obvious aggregation or fusion appeared in the concentration range of 0.25-5.00 mg/mL during storage. The in vitro release demonstrated that casein, especially glycosylated casein, could effectively protect EGCG from degradation in alkaline pH and displayed a slow and sustained release in intestinal fluid, which may be attributed to the inhibiting effects of casein binding on the motion freedom of EGCG. Fluorescence quenching spectra demonstrated that the steric hindrance induced by dextran could inhibit the interaction between casein and EGCG. These findings demonstrated that glycosylated casein could be used as a promising and effective nanocarrier for EGCG.