Chitosan–Unconjugated Bilirubin Microspheres Alleviate Dysbiosis, Immune Dysregulation, and Intestinal Barrier Damage in Ulcerative Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease marked by immune dysregulation, microbiota imbalance, and intestinal barrier damage. Unconjugated bilirubin (UCB) shows promise in treating UC due to its anti-inflammatory properties but is limited by poor solubility and potential toxicity. This study developed a chitosan-based controlled-release microsphere (CBMS) treatment to overcome these issues. CBMS utilizes the mucoadhesive properties of chitosan to achieve targeted, controlled UCB release in the colon, enhancing its stability and bioavailability. In a DSS-induced UC mouse model, CBMS alleviated clinical symptoms, reduced colon shortening, and improved histological outcomes, including reduced inflammation and enhanced mucosal repair. The mechanism involves CBMS retention in the intestinal lumen, UCB inactivation of digestive proteases, and restoration of microbiota balance, suppressing pro-inflammatory pathways. CBMS offers a promising new therapeutic strategy for UC and insights into polysaccharide-based drug delivery systems.