Dual-mechanism mucoadhesive hydrogel integrating pH-independent barriers and autophagy-driven immunotherapy for the treatment of ulcerative colitis

Abstract

Current therapies for ulcerative colitis (UC) face critical challenges, including systemic toxicity and inadequate mucosal regeneration. Herein, we present a pioneering dual-mechanism therapeutic platform integrating pH-independent acid-treated sucralfate (ASF) with autophagy-inducing spermidine (Spd) to synergistically address UC pathogenesis. Unlike conventional pH-dependent barrier therapies, ASF forms a mechanically tunable, injectable hydrogel that adheres robustly to colonic mucosa regardless of local pH. Spermidine was easily mounted into ASF hydrogel matrix via electrostatic interaction, with more than 90 % encapsulation efficiency. Moreover, the mechanical strength of ASF hydrogel was precisely modulated by adjusting spermidine amount in formula, making it suitable for effective gut mucosa coverage. Importantly, in vitro permeability test showed that spermidine-loaded ASF hydrogel (Spd-ASF) demonstrated the selective barrier functionality, blocking > 80 % of Escherichia coli and LPS penetration while allowing nutrient permeability. Moreover, micro-CT images demonstrated that rectally infused Spd-ASF hydrogel was uniformly adhered to the colon wall at least for 8 h. In DSS-induced colitis mice, rectally administrating Spd-ASF hydrogel uniquely restored colon length to near-normal levels (vs. 30 % shortening in controls), reduced proinflammatory cytokines (TNF-α, IL-6, IL-1β) by 60–75 %, and doubled goblet cell density. Mechanistically, Spd-ASF reprogrammed macrophage behavior by activating autophagy and enhancing efferocytosis, driving M2 polarization to resolve inflammation. Notably, Spd-ASF uniquely reversed dysbiosis, elevating beneficial Lactobacillus while suppressing colitis-associated Muribaculaceae and Clostridia. This study is the first to combine mucoadhesive biomaterial engineering with autophagy-mediated immunomodulation, offering a paradigm shift in UC therapy by simultaneously shielding the mucosa and reprogramming inflammatory pathways.

Statement of significance

Here, autophagy-inducing spermidine (Spd) and pH-independent acid-treated sucralfate (ASF) were combined to create the novel dual-mechanism hydrogel (Spd-ASF), which works in concert to combat UC pathogenesis. The selective barrier functioning of Spd-ASF hydrogel was established by its capacity to permit nutritional permeability while preventing the transfer of toxins (LPS) and pathogenic bacteria (E. coli). Additionally, rectally infused Spd-ASF hydrogel was consistently attached on the colon wall for at least eight hours, as seen by micro-CT images. Spd-ASF therapy doubled the density of goblet cells, decreased proinflammatory cytokines (TNF-α, IL-6, and IL-1β) by 60–75 %, boosted helpful Lactobacillus, and lowered pathogenic Muribaculaceae and Clostridia. It also restored colon length in DSS-induced colitis animals. Spd-ASF's therapeutic action was closely linked to promoting cellular efferocytosis and triggering macrophage autophagy.