Triggered protein release from calcium alginate/chitosan gastro-resistant capsules

This work aimed to develop gastro-resistant capsules, based on alginate (Alg), as an oral delivery system for enhanced bioavailability of proteins. Bovine Serum Albumin (BSA), selected as a model protein, has been encapsulated inside calcium alginate capsules, which have been coated with a thin layer of chitosan (CHT) to improve its robustness and delivery profile. BSA and sodium alginate aqueous mixtures were characterized by optical microscopy and dynamic light scattering, suggesting that BSA and sodium alginate form water-in-water coacervate droplets by ionic complexation. Encapsulation of BSA-Alg colloidal dispersions was performed by introducing the BSA-Alg mixtures in CaCl2 solutions. Thus, calcium alginate capsules were formed, which were subsequently coated with CHT. Encapsulation of BSA achieved ≈99% efficiency, the water content of capsules was ≈95wt% and the amount of chitosan coating in wet capsules was <0.017wt%. The stability of the capsules and the release of BSA were studied by several in vitro techniques, in simulated gastric and intestinal fluids. The addition of CHT as a coating material greatly improved the performance of the capsules, compared to that of capsules without CHT. The results of calcium-chitosan alginate capsules showed that they are stable in water at neutral pH and remain almost intact in simulated gastric fluid, but rapidly disintegrate when further treated with simulated intestinal fluid. These results demonstrated that calcium alginate-chitosan capsules can protect proteins from harsh gastric conditions and release their content at intestinal pH, demonstrating their potential application in the field of oral protein delivery.