Membrane destruction-mediated antibacterial activity of tungsten disulfide (WS2)

Abstract

The antibacterial activities of tungsten disulfide (WS₂) nanosheets against two representative bacterial strains: Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were evaluated by colony-forming unit (CFU) studies. The WS₂ samples demonstrate a time and concentration dependent antibacterial activity (retardation of bacterial growth) for both bacterial strains. Morphology analyses reveal that WS₂ nanosheets adhere to the bacterial surfaces, resulting in robust inhibition of cell proliferation once a bacterium is fully covered with this nanomaterial. More importantly, the intimate contact of WS₂ nanosheets with a bacterium cell membrane can cause serious damage to the membrane integrity, and subsequently the cell death. On the other hand, the reactive oxygen species (ROS) generated by WS₂ nanosheets are found to be modest regardless of the WS₂ concentration, which is contradictory to the case of its structural analogue, MoS₂, where ROS also play a significant role in its antibacterial activity. Taken together, our findings provide a detailed understanding of the antibacterial mechanism of WS₂ nanosheets, which might help promote their potential applications in biomedical fields.