Oral carbon dot nanozymes with red fluorescence and superoxide dismutase-like activity for colitis bioimaging and inflammation management

Disturbed intestinal microbiota and abnormally high levels of reactive oxygen species (ROS) in the colon are important factors in the pathogenesis of ulcerative colitis (UC). Therefore, modulation of intestinal microbiota and ROS synchronously in the inflamed colon are effective approach for UC management. In this study, we developed carbon dots (C-dots) nanozymes derived from glutathione and biotin via a solvothermal method. We found that the synthesized C-dots nanozymes possessed both the enzymatic activity of superoxide dismutase (SOD) and the ability to regulate intestinal microbiota. The in vitro experiments showed that C-dots nanozymes could eliminate excess ROS, protect cells from oxidative stress, and reduce the expression of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). In the mice models of UC, oral administration of C-dots nanozymes in chitosan/alginate hydrogel was found effective in alleviating colonic inflammation such as endoscopic and pathological remission with preventive and therapeutic effects. In addition, C-dots showed a remarkable ability to modulate the composition of the gut microbiota as well as increased potential probiotics and decreased pathogenic microorganisms. Moreover, with satisfactory red fluorescence, C-dots showed feasible bioimaging for intestinal inflammation. Overall, C-dots nanozymes achieved desirable preventive and therapeutic effects for UC by scavenging ROS and modulating the intestinal microbiota, coupled with bioimaging properties, C-dots nanozymes provide a potential approach for the clinical treatment of UC patients.