Dispersible MoS2 micro-sheets induced a proinflammatory response and apoptosis in the gills and liver of adult zebrafish

Molybdenum disulfide (MoS2), one of the next-generation two-dimensional materials (2DMs), has attracted increasing attention due to its unique physicochemical properties. However, the aquatic toxicity of dispersible MoS2 is still unknown. Herein, we synthesized chitosan functionalized MoS2 (CS-MoS2) micro-sheets with a satisfying water-dispersible performance. The average length and width of the as-prepared CS-MoS2 micro-sheets were 5.04 mm and 3.12 mm, respectively, and they had a pristine 2H polymorph. The toxicity of CS-MoS2 micro-sheets was assessed by investigating the organs, gills and liver of adult zebrafish. We found that exposure to high concentrations of CS-MoS2 micro-sheets (10 mg L-1 and 20 mg L-1) led to lamellar fusions in the gills, and significant localized lesions, such as peripheral nuclei and vacuole formation, in the liver. In addition, treatment with 20 mg L-1 CS-MoS2 micro-sheets suppressed gene expression of antioxidant enzymes (e.g., CAT and GPx1a gene) and induced the expression levels of the proinflammatory response and apoptosis (e.g., IL-1 beta IL-6, and AIF gene) in gill and liver tissues. Further, reactive oxygen species (ROS) were generated upon treatment with 20 mg L-1 CS-MoS2 micro-sheets in both organs. To the best of our knowledge, this is the first investigation of the aquatic toxicity of dispersible MoS2 in zebrafish, and further highlights the potential environmental risk of MoS2.