Immunohistochemical results showed that the S100 NP@DA group could significantly up-regulate the expression of Occludin, ZO-1, and Claudin-1, which have a low level in colitis mice, and the arrows showed Occludin, ZO-1, and Claudin-1 deletion in the DSS and mPDA@DA group (Fig. 5l), further demonstrating the protection and repair of epithelial barrier by pathologically catalyzed PDA coating. Here, OCLN is linked to colitis.