Cytotoxicity of Exfoliated Transition‐Metal Dichalcogenides (MoS2, WS2, and WSe2) is Lower Than That of Graphene and its Analogues

Abstract

Studies involving transition‐metal dichalcogenides (TMDs) have been around for many decades and in recent years, many were focused on using TMDs to synthesize inorganic analogues of carbon nanotubes, fullerene, as well as graphene and its derivatives with the ultimate aim of employing these materials into consumer products. In view of this rising trend, we investigated the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS 2, WS 2, and WSe 2, and compared their toxicological effects with graphene oxides and halogenated graphenes to find out whether these inorganic analogues of graphenes and derivatives would show improved biocompatibility. Based on the cell viability assessments using methylthiazolyldiphenyl‐tetrazolium bromide (MTT) and water‐soluble tetrazolium salt (WST‐8) assays on human lung carcinoma epithelial cells (A549) following a 24 h exposure to varying concentrations of the three exTMDs, it was concluded that MoS 2 and WS 2 nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe 2 exhibited dose‐dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL−1; the higher cytotoxicity displayed by WSe 2 might be linked to the identity of the chalcogen. In comparison with graphene oxides and halogenated graphenes, MoS 2 and WS 2 were much less hazardous, whereas WSe 2 showed similar degree of cytotoxicity. Future in‐depth studies should be built upon this first work on the in vitro cytotoxicity of MoS 2 and WS 2 to ensure that they do not pose acute toxicity. Lastly, nanomaterial‐induced interference control experiments revealed that exTMDs were capable of reacting with MTT assay viability markers in the absence of cells, but not with WST‐8 assay. This suggests that the MTT assay is not suitable for measuring the cytotoxicity of exTMDs because inflated results will be obtained, giving false impressions that the materials are less toxic.