*3.4. DAPI*/*PI Staining*

Cells were treated with PN for 48 h, fixed with 4% paraformaldehyde (Sigma), washed with PBS, and stained with DAPI (4-,6-diamidino-2-phenylindole, Sigma) to detect cell nuclei and with PI (propidium iodide, Sigma) to detect dead cells in the dark. Stained cells were then observed under a fluorescence microscope (EVOS®, Thermo Scientific, Waltham, MA, USA).
