Development of a food-compatible dual-coating system based on coordination chemistry and bioadhesion for enhancing the oral delivery performance of probiotics.

The oral delivery performance of probiotics is often compromised by their susceptibility to inactivation during gastrointestinal transit. To address this challenge, we constructed a dual-coating system from food-compatible coating components through coordination-driven self-assembly and surface engineering. The inner metal-phenolic network (MPN), formed by tannic acid and Ca2+, provided structural protection and antioxidant capacity, while the outer sericin layer was introduced to improve mucus-associated adhesion. Using Escherichia coli Nissle 1917 as a model probiotic, the dual-coated formulation (EcN@TAC@Ser) showed improved survival during simulated gastrointestinal digestion, with viable counts maintained above 106 CFU/mL. It also exhibited enhanced free-radical scavenging activity and storage stability. The sericin-containing dual coating further improved intestinal retention in vivo, as indicated by fluorescence imaging and bacterial enumeration from intestinal samples. This work provides a cell-surface engineering strategy for improving the gastrointestinal survival and intestinal retention of probiotics.