Two-dimensional molybdenum disulfide nanosheets evoke nitric oxide-dependent antibacterial effects

Nanomaterials are currently being explored as novel antimicrobial agents. In this study, we first investigated the ability of two-dimensional (2D) molybdenum disulfide (MoS₂) nanosheets to trigger neutrophil extracellular traps (NETs) using neutrophil-differentiated HL-60 cells as well as primary human peripheral blood neutrophils. We then addressed whether the MoS₂ nanosheets themselves function as antibacterial agents. We found that MoS₂ and Na₂MoO₄ both triggered NETs, as evidenced by the quantification of neutrophil elastase (NE) activity and immunofluorescence staining of extracellular NE, as well as scanning electron microscopy. The release of NETs was found to be nitric oxide (NO)-dependent. We also found that the MoS₂ nanosheets but not the soluble salt prompted acellular NO production in the presence of NaNO₂. The acellular generation of NO, suggestive of nanozyme properties of the MoS₂ nanosheets, was demonstrated by electron paramagnetic resonance analysis. Electrochemical analysis using cyclic voltammetry confirmed the redox transition of the MoS₂ nanosheets. Finally, MoS₂ nanosheets inhibited the growth of Escherichia coli in the presence of sodium nitrate. Taken together, MoS₂ nanosheets triggered cellular effects as well as acellular antibacterial effects, and we provided evidence for nitrite reductase-like properties of MoS₂.