Synergistic Therapeutic Efficacy of Engineered Probiotics Embedded in Self-Assembling Keratin Hydrogels for Ulcerative Colitis Treatment

Efficient oral delivery and sustained viability of probiotics remain significant obstacles to the clinical translation of live biotherapeutics. Therefore, in this study, we developed self-assembling keratin hydrogels derived from feather waste using a disulfide shuffling strategy for probiotic encapsulation. This cost-effective and scalable approach substantially improved the gastrointestinal tolerance and oral bioavailability of multiple probiotics, including <i>Escherichia coli</i> Nissle 1917 (EcN), <i>Bacillus licheniformis</i>, <i>Lactococcus lactis</i>, and <i>Bifidobacterium bifidum</i>. To achieve site-specific release in the intestinal tract, EcN was engineered to express keratinase (EcNker), enabling hydrogel degradation in the gut. In dextran sulfate sodium-induced colitis model mice, hydrogel-encapsulated EcNker exhibited markedly superior therapeutic efficacy over unencapsulated probiotics, as indicated by the amelioration of clinical symptoms, restoration of colon histology, attenuation of intestinal apoptosis, and normalization of inflammatory cytokine profiles. Mechanistically, hydrogel-encapsulated EcNker treatment restored the gut barrier integrity by upregulating the tight junction protein levels, modulating gut microbiota by increasing the number of beneficial genera, and enhancing short-chain fatty acid production. Collectively, our findings highlight the potential of keratin hydrogels as universal biocompatible and efficient delivery platforms for orally engineered probiotics to treat colonic colitis and other diseases.