Mucoadhesive hydrogels with multifunctional properties such as gastric acid resistance and sustained drug release in the intestinal tract are highly desirable for the oral treatment of inflammatory bowel diseases (IBDs). Polyphenols are proven to have great efficacies compared with the first-line drugs for IBD treatments. We recently reported that gallic acid (GA) was capable of forming a hydrogel. However, this hydrogel is prone to easy degradation and poor adhesion in vivo. To tackle this problem, the current study introduced sodium alginate (SA) to form a gallic acid/sodium alginate hybrid hydrogel (GAS). As expected, the GAS hydrogel showed excellent antiacid, mucoadhesive, and sustained degradation properties in the intestinal tract. In vitro studies demonstrated that the GAS hydrogel significantly alleviated ulcerative colitis (UC) in mice. The colonic length of the GAS group (7.75 ± 0.38 cm) was significantly longer than that of the UC group (6.12 ± 0.25 cm). The disease activity index (DAI) value of the UC group was (5.5 ± 0.57), which was markedly higher than that of the GAS group (2.5 ± 0.65). The GAS hydrogel also could inhibit the expression of inflammatory cytokines, regulating macrophage polarization and improving the intestinal mucosal barrier functions. All these results indicated that the GAS hydrogel was an ideal candidate for oral treatment of UC.
Keywords: gastric acid resistance; hybrid hydrogel; mucoadhesion; mucosal barrier repair; ulcerative colitis.