Designing Novel pH-Induced Chitosan–Gum Odina Complex Coacervates for Colon Targeting

This paper investigates the design of novel polyelectrolyte complex (PEC) coacervates of chitosan (Ch) with gum Odina (GO) as potential candidates for colon targeting. Potentiometric titration experiments established that 1:1 charge stoichiometry occurred at a Ch/GO weight ratio of 1:5. The coacervate formed at pH 4.5 displayed the highest storage modulus (G′) values. FTIR, XPS, WAXS, TGA, and DSC results suggested the strong ionic (NH3+···COO–) bond formation between these two biopolymers. Through in vitro viability tests, the pH-induced PECs were shown to be nontoxic. In vitro biodegradation rates of their microspheres revealed insolubility in simulated gastric fluid and simulated intestinal fluid and degradation by cell-associated portions of rat cecal and colonic enzymes rather than the extracellular portions. The microsphere of pH 3.0 showed the highest degradation, and LVSEM micrographs revealed notably high amount of macropores in cell-associated enzymes, in contrast to extracellular enzymes.