Bioresponsive Polymer Systems for Site-Specific Colonic Activation

Abstract Inflammatory bowel disease requires engineered systems that can stay stable in the upper gastrointestinal tract and activate only when they reach the colon. In this study, we developed a bioresponsive polymer system using pH-responsive and hydrophobic Eudragit® polymers to create colon-activated Mesalazine microspheres. The microcarriers were produced through an aqueous spray-drying process and evaluated for their structure, stability, and functional response in simulated gastric, intestinal, and colonic environments. They remained stable under acidic and near-neutral pH, releasing less than 25% of the drug in the first 6 h. At colonic pH, the polymer matrix ionized and swelled, triggering a complete and controlled release of Mesalazine. Structural and molecular analyses (scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction) confirmed the formation of a stable co-amorphous drug–polymer network with smooth and uniform particle morphology. Overall, this work demonstrates a bioengineered pH-responsive system capable of protecting Mesalazine during gastrointestinal transit and releasing it selectively at the site of inflammation, offering a safe and scalable platform for colon-targeted inflammatory bowel disease therapy.