Structural and mechanistic exploration in the development of floating drug delivery systems using calcium-pectinate gels with sodium bicarbonate as CO2 gas-forming agent

This study used external ionotropic gelation to design floatable calcium-pectinate hydrogels incorporating (-)-Epigallocatechin-3-gallate (EGCG) as a model drug. Sodium bicarbonate at varying concentrations (0 %, 1 %, 3 %, and 5 % w/v) served as a gas-forming agent to produce carbon dioxide in simulated gastric fluid (SGF). The reaction between sodium bicarbonate and released protons during gelation formed a limited number of holes in the gel. Results showed the size and number of holes correlated with the 3D structure of pectin, with denser, rigid area forming smaller holes and softer areas forming larger holes. Moreover, the increased local pH from sodium bicarbonate led to EGCG degradation, especially in the softer parts of the gel. The dosage forms exhibited high encapsulation efficiency, with EGCG release in SGF following polymer matrix erosion and relaxation. Higher sodium bicarbonate concentrations accelerated EGCG release, highlighting the impact of CO2 generation on drug release kinetics. This study demonstrates the potential of anisotropic gels as innovative drug delivery systems for controlled release in the stomach.