Low Cytotoxicity and Genotoxicity of Two-Dimensional MoS<sub>2</sub> and WS<sub>2</sub>

Atomically thin transition-metal dichalcogenides (TMDs) have attracted considerable interest because of their unique combination of properties, including photoluminescence, high lubricity, flexibility, and catalytic activity. These unique properties suggest future uses for TMDs in medical applications such as orthodontics, endoscopy, and optogenetics. However, few studies thus far have investigated the biocompatibility of mechanically exfoliated and chemical vapor deposition (CVD)-grown pristine two-dimensional TMDs. Here, we evaluate pristine molybdenum disulfide (MoS<sub>2</sub>) and tungsten disulfide (WS<sub>2</sub>) in a series of biocompatibility tests, including live–dead cell assays, reactive oxygen species (ROS) generation assays, and direct assessment of cellular morphology of TMD-exposed human epithelial kidney cells (HEK293f). Genotoxicity and genetic mutagenesis were also evaluated for these materials via the Ames Fluctuation test with the bacterial strain <i>S. typhimurium</i> TA100. Scanning electron microscopy of cultured HEK293f cells in direct contact with MoS<sub>2</sub> and WS<sub>2</sub> showed no impact on cell morphology. HEK293f cell viability, evaluated by both live–dead fluorescence labeling to detect acute toxicity and ROS to monitor for apoptosis, was unaffected by these materials. Exposure of bacterial cells to these TMDs failed to generate genetic mutation. Together, these findings demonstrate that neither mechanically exfoliated nor CVD-grown TMDs are deleterious to cellular viability or induce genetic defects. Thus, these TMDs appear biocompatible for future application in medical devices.