POLYMER-BASED INTERFACE TARGETING INFLAMMATION IN ULCERATIVE COLITIS

Abstract A major hurdle in the treatment of inflammatory bowel disease (IBD) is the lack of effective drug carriers that can precisely deliver the required amount of drug to the sites of inflammation. Available therapies have limited efficacy or severe side effects, largely because of the low concentration of active drugs at the disease sites and non-specific systemic absorption of the administered drugs. Drug delivery targeting the sites of intestinal inflammation offers an approach to maximize therapeutic efficacy while minimizing adverse side effects. We focus on developing formulations that can provide improved local drug administration in the treatment of ulcerative colitis (UC), one of the two main types of IBD. Targeting sites of inflammation in the gastrointestinal tract can be achieved using drug delivery systems that exploit pathophysiological features of the inflamed intestine. Our previous study showed preferential adhesion of a negatively charged small-molecule-based hydrogel to the inflamed colon in murine models of colitis and biopsies from UC patients; further, a corticosteroid drug delivered by this hydrogel demonstrated an improved efficacy compared to the drug alone. Based on our previous experience, we expanded the small-molecule-based hydrogel to polymer-based hydrogels for enhanced selective targeting. We designed the material so that it has a strong affinity towards ulcers. Through molecular structure design, we functionalized thermo-responsive poly(N-isopropylacrylamide) (PNIPAM)-based polymers to modulate the physicochemical properties of the materials and compared the resultant polymers’ gelation and adhesion to the inflamed colon in dextran sulfate sodium (DSS)-induced colitis in mice. We showed that both the types of chemical modification and polymer molecular weight affected the adhesion of the resultant hydrogels to the inflamed colon. We further quantified the disease parameters of colitis for individual mice and correlated the colitis parameters with polymers’ adhesion. Our study suggests a new strategy for targeting the inflamed colon through harnessing charge-mediated interaction and thermo-responsiveness of PNIPAM-based polymers. By adhering to the inflamed mucosa, our delivery system has the potential to maintain the drug locally at the active ulcer sites where it is needed, thereby minimizing the adverse effects of drugs on the healthy tissue. The examination of these polymeric hydrogels’ mucosal binding provides a further understanding of interactions between the polymers and the biological interface in colitis. These studies were performed in preclinical models of UC that develop colitis similar to human UC, as a prerequisite for future studies.