Microencapsulation of <i>Bifidobacterium lactis</i> and <i>Lactobacillus plantarum</i> within a Novel Polysaccharide-Based Core–Shell Formulation: Improving Probiotic Viability and Mucoadhesion

Probiotics health benefits are hampered by long-term storage, gastrointestinal transit, and lack of adequate colonization within the colon. To this end, we have designed a core-shell structure that features an acid resistant core formulation with low water activity composed of alginate, hydroxypropyl methyl cellulose, and gellan gum (AHG) and a mucoadhesive shell made from chemically modified carboxymethyl chitosan with polyethylenimine (PEI-CMC). The structure of the core-shell microparticles was examined using scanning electron microscopy, and rheological measurements confirmed the improved ionic interactions between the core and the shell using the PEI-modified CMC. Simulated release from core-shell microparticles using polystyrene beads showed preferential release under intestinal conditions. PEI-CMC coating yielded improvements in mucoadhesion that was consistent with a positive shift in surface charge of the particles. Ex vivo studies using <i>Bifidobacterium lactis</i> probiotic bacteria demonstrated a 1.1 × 10⁵-fold improvement in bacterial viability with encapsulation under storage conditions of high humidity and temperature (30 °C). When exposed to simulated gastric fluid, encapsulation increased the probiotic viability by 3.0 × 10²-fold. In vivo studies utilizing bioluminescent <i>Lactobacillus plantarum</i> in mice revealed that encapsulation extended the duration of the signal within the gut and resulted in higher plate counts in suspensions isolated from the cecum. Conversely, we observed an abrupt loss of signal in the gut of the free probiotic. In conclusion, this core-shell system is suitable for improving probiotic shelf life and maximizing delivery to and retention by the colon.