Mucoadhesive microcapsules for the delivery of probiotic-derived extracellular vesicles
Abstract Probiotic efficacy depends not only on gastrointestinal survival but on mucosal adhesion and the capacity to deliver bioactive molecules at the intestinal surface. This study optimized a whey protein isolate (WPI)–chitosan (CS) matrix for spray drying microencapsulation of Lacticaseibacillus casei BL23 using central composite design, targeting enhanced mucoadhesion while preserving bacterial viability and extracellular vesicle (EV) secretion capacity. The optimal formulation, WPI 20%-CS 0.5%, yielded viable counts within recommended probiotic ranges (6.6 × 10⁹ CFU/g) and a ~ 77-fold mucoadhesion increase relative to WPI alone, supporting extended intestinal residence time and potentially enhanced therapeutic efficacy. Storage stability was confirmed at 4°C and − 20°C, and microcapsules were predominantly spherical (2–15 μm), suitable for food applications. Microencapsulation also significantly enhanced gastrointestinal survival, with encapsulated bacteria showing only a ~ 2-log reduction after the gastric phase compared to ~ 6-log for free bacteria. Fermentative capacity in reconstituted milk was fully preserved, with reduced syneresis indicative of improved gel stability. Critically, this system ensures the delivery of probiotic-derived extracellular vesicles (EVs) at the intestinal interface. We demonstrate that EV secretion is maintained post-encapsulation, yielding vesicles (70–100 nm) enriched in p40 and p75 proteins. To our knowledge, this is the first evidence that spray-dried microcapsules can effectively serve as a delivery platform for postbiotic EVs by preserving the functional secretory machinery of the encapsulated bacteria. These findings position mucoadhesive WPI-CS microcapsules as a robust strategy for the targeted delivery of EVs in nutraceutical and functional food development. Key points • Whey protein-chitosan microencapsulation boosts mucoadhesion ~77-fold in vitro. • Microencapsulation enhances probiotic survival across gastrointestinal conditions. • Spray-drying preserves the probiotic machinery for postbiotic EV secretion.