Surface Defects Regulate the Bioenergetic Response of Earthworm Coelomocytes to Molybdenum Disulfide Nanosheets.

Two-dimensional molybdenum disulfide (2D MoS) nanomaterials are seeing increased use in several areas, and this will lead to their inevitable release into soils. Surface defects can occur on MoS nanosheets during synthesis or during environmental aging processes. The mechanisms of MoS nanosheet toxicity to soil invertebrates and the role of surface defects in that toxicity have not been fully elucidated. We integrated traditional toxicity end points, targeted energy metabolomics, and transcriptomics to compare the mechanistic differences in the toxicity of defect-free and defect-rich MoS nanosheets (DF-MoS and DR-MoS) to using a coelomocyte-based assessment model. After organism-level exposure to DF-MoS for 96 h at 10 and 100 mg Mo/L, cellular reactive oxygen species (ROS) levels were elevated by 25.6-96.6% and the activity of mitochondrial respiratory electron transport chain (Mito-RETC) complex III was inhibited by 9.7-19.4%. The tricarboxylic acid cycling and glycolysis were also disrupted. DF-MoS preferentially up-regulated subcellular component motility processes related to microtubules and caused mitochondrial fission. Unlike DF-MoS, DR-MoS triggered an increased degree of mitochondrial fusion, as well as more severe oxidative stress. The activities of Mito-RETC complexes (I, III, IV, V) associated with oxidative phosphorylation were significantly inhibited by 22.8-68.6%. Meanwhile, apoptotic pathways were activated upon DR-MoS exposure, which together with the depolarization of mitochondrial membrane potential, mediated significant apoptosis. In turn, genes related to cellular homeostasis and energy release were up-regulated to compensate for DR-MoS-induced energy deprivation. Our study indicates that MoS nanosheets have nanospecific effects on and also that the role of surface defects from synthesis or that accumulate from environmental impacts needs to be fully considered when evaluating the toxicity of these 2D materials.