Disulfide Cross-Linked Thiolated Chitosan/Oxidized Dextran–Oleylamine Micelle–Hydrogel System with pH/ROS Dual-Responsive Cascade Drug Release for Integrated Colon Targeting and Mucosal Repair in Inflammatory Bowel Disease

Background: Oral colon-targeted delivery for inflammatory bowel disease (IBD) faces significant challenges, including limited gastrointestinal stability, premature drug release, and insufficient mucosal retention. Methods: To address these limitations, a mucoadhesive polysaccharide-based composite hydrogel incorporating prednisolone-loaded polymeric micelles was developed to enhance colonic delivery and promote mucosal repair. Amphiphilic oxidized dextran–oleylamine (ODEX-OA) copolymers were synthesized to self-assemble into prednisolone-loaded micelles. These micelles were subsequently embedded within a thiolated chitosan (CSSH) hydrogel through a Schiff base reaction, yielding the ODEX-OA-Pred-CSSH composite. The resulting system was comprehensively characterized for particle size, mucoadhesion, degradation, and pH/ROS dual-responsive drug release. Its colon-targeting capability and therapeutic efficacy were subsequently assessed in a dextran sulfate sodium (DSS)-induced colitis mouse model. Results: In vitro, the composite hydrogel demonstrated nanoscale micellar size, enhanced drug release kinetics under simulated inflammatory colonic conditions, and prolonged colonic retention for up to 24 h following oral administration. In vivo, studies confirmed that ODEX-OA-Pred-CSSH significantly alleviated colitis, evidenced by a reduced disease activity index, diminished pro-inflammatory cytokine levels, restored colon length, decreased spleen index, and improved histological mucosal repair. Conclusions: These findings collectively suggest that this mucoadhesive micelle–hydrogel composite represents a promising and effective oral colon-targeted platform for the treatment of IBD.