Microfluidic fabrication of enteric-coated liquid-core ATPS capsules for colon-targeted probiotic delivery

Oral delivery of live probiotics is limited by severe viability loss during passage through the stomach and small intestine. In this study, we developed an integrated experimental–numerical microfluidic platform for colon-targeted delivery of E. coli Nissle 1917 (EcN) using aqueous two-phase system (ATPS) liquid-core/hydrogel-shell capsules. A PEG-based core containing EcN was encapsulated within a dextran/alginate/Ca-EDTA shell, which was ionically crosslinked on-chip, then further functionalized with chitosan and Eudragit S100 to improve enteric protection. A validated volume-of-fluid computational model was used to clarify how dispersed-phase viscosity and channel confinement affect droplet breakup, internal recirculation, and the formation of one-core versus two-core double-emulsion structures. Experimentally, one-core capsules showed significantly higher encapsulation efficiency than two-core capsules (94.1 ± 0.9% vs. 85.3 ± 2.6%, p < 0.01). The selected Eudragit nanoparticles had a mean diameter of about 69 nm and enabled uniform coating. During simulated gastrointestinal transit, uncoated capsules lost viability completely after 2 h in gastric fluid, whereas chitosan-coated and Eudragit–chitosan-coated capsules retained 89% and 95.2% viability, respectively, and remained above 87% after 6 h. Release was negligible in gastric fluid, limited in intestinal fluid (∼6.7% at 6 h), and reached ∼95–100% in dextranase-containing simulated colonic fluid by 7–8 h. These results demonstrate a scalable platform for protected upper-GI transit and enzyme-responsive colon-targeted probiotic release.