| Inflammatory bowel diseases(IBD)is a chronic and nonspecific inflammation of the colon that occurs with symptoms such as stomachache,diarrhoea and hemafecia,which seriously affects the daily life of patients.In recent years,the incidence of IBD has increased significantly in our country and some other developing countries.At present,because of the treatment of IBD is mainly to relieve symptoms,it cannot be completely cured.Some traditional drugs such as immunosuppressants and antibiotics,etc.,have low solubility,poor stability and other defects.And these drugs may aggravate the intestinal immune system disorders and intestinal flora imbalance caused by IBD,even have severe side-effects.For the past few years,probiotic therapy is an emerging treatment for IBD.Probiotics can play a role in remodeling intestinal flora,inhibiting inflammatory response and regulating intestinal immunity for the treatment of IBD.However,existing oral probiotic formulations generally suffer from low oral availability and short colonic residence time,resulting in poor efficacy of probiotic therapy.In this study,we constructed a novel probiotic delivery system to maximize the efficacy of probiotic therapy.The delivery system uses methapropene-modified hyaluronic acid(Me HA)as the framework,and the dithiol linker containing thioketal as the crosslinking agent,and forms a reactive oxygen species(ROS)-responsive hyaluronic acid hydrogel(HA-gel)responsive by thiol-ene click reaction under physiological conditions.And the hydrogel is loaded with Lactobacillus reuteri(LR)to obtain the probiotic delivery system HA-LR.Firstly,the physical properties and microstructures of the hydrogel were tested by rheological experiments and scanning electron microscopy.Subsequently,the protective effect of hydrogel on LR in the environment gastric juice and small intestinal fluid was tested by in vitro simulated digestion experiments.At the same time,for researching the retention of HA-LR in the colon,we tested the adhesion effect of HA-gel at the site of colonic inflammation in vitro and in vivo,respectively.Finally,we used a mouse IBD model induced by Dextran Sulfate Sodium(DSS)to evaluate the treatment efficacy of HA-LR on IBD in vivo,and preliminarily explore its therapeutic mechanism by pathological means.Experiments showed that LR was successfully wrapped in hydrogel,and the hydrogel had a significant protective effect on LR,and the survival rate of LR encapsulated in gastric juice was 106 times that of LR unencapsulated.The result ensured that LR could reach the colon smoothly and maintain vitality.Subsequently,we verified that the hydrogel can selectively adhere to the inflammatory site of the colon through positive and negative charge interactions,significantly prolonging the retention time of LR in the inflamed colon.After mouse given the hydrogel by oral administration later,higher abundances of LR were still detected in mouse feces.Upon reaching the site of colonic inflammation,the hydrogel was oxidized and disconnected thioketal bonds to degrade the hydrogel structure because of high concentrations of ROS,releasing encapsulated LR.At the same time,it greatly removed the excess ROS and significantly reduces the oxidative damage of cells.Finally,in vivo experiments showed that HA-LR had a significant therapeutic effect on DSS-induced IBD in mice.Compared to unencapsulated LR,HA-LR significantly improved the survival rate of mice,reduced IBD symptoms,inhibited the secretion of pro-inflammatory cytokines and increased the secretion of anti-inflammatory cytokines.In summary,we constructed a ROS-responsive hydrogel system targeting sites of intestinal inflammation and it successfully used for oral delivery of LR for the treatment of IBD.The system has good targeting,controlled release and biological safety,which provides a great research direction in the development of oral delivery systems for drugs and bioactive agents related to intestinal inflammation. |
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