Fig. 4

a Confocal images of A549 cells after various treatments, with HELF cells as a control. In this experiment, A549 and HELF cells were incubated with fluorescence labeled-MoS₂ nanosheets (MoS₂-PEG-Biotin-RB or MoS₂-PEG-RB) for 2 h, washed with PBS, and stained with cell nucleus dye prior to the confocal microscopy observation. b Flow cytometry analysis of the intracellular RB fluorescence intensity in (a)