Development and characteristics of layered EGCG/Montmorillonite hybrid: An oral controlled-release formulation of EGCG

Abstract

An oral controlled-release formulation of epigallocatechin-3-gallate (EGCG) was developed by intercalating EGCG into the interlayer space of Food and Drug Administration-approved mucoadhesive montmorillonite (Mt) nanolayers, and characterized by ultraviolet–visible, X-ray diffraction, Fourier transform infrared, and thermogravimetry. The EGCG intercalation was only possible at acidic pH, and occurred through electrostatic and hydrogen bonding interactions allowing restacking of exfoliated Mt nanolayers with EGCG molecules. It was inferred that EGCG molecules were adsorbed flat on the interlayer surface of Mt in a monolayer and formed two-sided hydrogen bonds with the Mt faces, leading to a ∼2-fold increase in the EGCG decomposition temperature. A maximum EGCG loading of ∼40 wt% was achieved at pH 3, reaction time 1 h, and EGCG:Mt ratio 40:10 mg/mL. The EGCG/Mt hybrid showed a sustained release of EGCG in simulated gastric and intestinal fluids in a pH-dependent manner. Deprotonation of EGCG was responsible for further EGCG release at pH 7.4 compared to pH 1.2. The release profiles were fitted to the parabolic diffusion and Bhaskar models, implying that the release was controlled by a diffusion process. These results suggest that Mt with a high loading capacity can be used as the controlled-release nanocarrier of EGCG in oral administration.