Construction and characterization of probiotic intestinal-targeted delivery system based on complex coacervation and double-emulsion structure

The objective of this research was to formulate a sophisticated probiotic intestinal-targeted delivery system employing GEL (Gelatin) and CMC (Carboxymethyl Cellulose) via intricate complex coacervation and double-emulsion structure. RSM (Response Surface Methodology) screening of cryoprotectants was undertaken and the digestive kinetic characteristics of microcapsules were comprehensively evaluated in simulated in vitro release environment. Upon optimization using response surface design, bacterial suspension was prepared using composite cryoprotectant composed of 3.07 wt% MNT (Mannitol), 4.42 wt% TCP (Taxus cuspidata polysaccharides) and 2.01 wt% GEL, achieving a cell recovery rate of 83.21%, which was 70.8% higher than free cells. The freeze-dried microcapsules presented in a stabilized bilayer system, the cell concentration after encapsulation was 8.66 log CFU/g, with encapsulation efficiency reaching 88.17%, and the particle size distribution concentrated at 299.05 μm/d. GEL and CMC conjugate through the interaction of positive and negative ions to form a complex polymer under pH of 3.5. Deprotonation occurs while pH changes in intestinal environment, enabling controlled release. In vitro release kinetics by Hixson-Crowell was closer than Higuchi model, the survival rate of encapsulated cells reached 83.64% in simulated gastric fluid, representing a 56.15% increase compared to free cells. After 6-weeks of storage in low-humidity environment at −18 °C, the recovery rate remained at 94.59%, representing a 69.17% increase compared to free cells. This research offer guiding principles and insights for future comparable research.