Rewiring Tryptophan Metabolism <i>via</i> Programmable Probiotic Integrated by Dual-Layered Microcapsule Protects against Inflammatory Bowel Disease in Mice

Intestinal dysbiosis and the associated l-tryptophan metabolic disorder are pivotal in inflammatory bowel disease progression, leading to a compromised intestinal barrier integrity. Remedying the dysfunction in tryptophan metabolism has emerged as a promising therapeutic strategy. Herein, we reprogram the tryptophan metabolism <i>in situ</i> by EcN-TRP@A/G, encapsulating the engineered probiotic, EcN-TRP, with enhanced tryptophan synthesis capacity, for sustained modulation, thereby restoring intestinal barrier function and microbial homeostasis. The pH-responsive dual-layered EcN-TRP@A/G microcapsule developed <i>via</i> high-voltage electrospraying and liquid interface self-assembly, preserved probiotic viability in the harsh gastrointestinal milieu, and facilitated targeted colon release. Bioluminescent tracking in mice reveals a 22.84-fold increase in EcN-TRP@A/G viability and distribution compared to naked EcN-TRP. Targeted metabolomics highlights EcN-TRP@A/G's modulation of the tryptophan-indole pathway. Oral administration of EcN-TRP@A/G sustained elevates indole metabolites, particularly indole-3-acetic acid and indole-3-propionic acid, in colon tissue for up to 7 days. In IBD mice, EcN-TRP@A/G improves intestinal permeability, reduces inflammation, and recovers the gut microbiome by enhancing beneficial bacteria abundance like <i>Prevotellaceae_UCG-001</i> and <i>Anaerostipes</i> while suppressing pathogenic strains like <i>Escherichia</i>-<i>Shigella</i>. Our findings offer a cost-effective approach, harnessing the probiotic metabolic potential <i>in situ</i> through engineered modifications for effective IBD treatment.