Dual-responsive microgel beads prepared from pectin-stabilized emulsions for the controlled release of synbiotics to ameliorate ulcerative colitis.

The benefits of synbiotics in ulcerative colitis are now supported by a growing amount of evidence. However, achieving its targeted delivery in vivo and reaching effective doses for therapeutic effects remains to be explored. To further explore the potential role of synbiotics in alleviating ulcerative colitis, this study designed a dual-response "egg-box" shaped microgel microsphere for targeted delivery and precise release of synbiotics. The internal "egg" structure was constructed using an apple pectin-zein hybrid particles (AZHPs) stabilized W1/O/W2 double emulsions system, while a dense network formed by poly-L-lysine (PLL) and calcium alginate constituted the protective "box" shell. We investigated the physicochemical characteristics of W1/O/W2 double emulsions prepared with different concentrations of AZHPs. The synbiotics-loaded W1/O/W2 double emulsions were coated with PLL and calcium alginate to prepare microgel beads. In vitro digestion results demonstrated that the survival rate of probiotics within the microgel beads was significantly higher than that in a free state. Oral microgel beads alleviate colitis by modulating tight junction proteins (ZO-1, Claudin 1 and Occludin), reducing inflammatory factors (IL-1β, IL-6 and TNF-α), promoting the production of short-chain fatty acids. After treatment with EPMB, the number of Firmicutes in the intestinal flora increased while the number of Bacteroidetes decreased, and synbiotics intervention successfully restored the abundance of gut microbiota. This indicated that the loaded synbiotics "egg-box" shaped microgel beads offer a new option for the current treatment of colitis.