Cells were grown to confluence in a 12 well-plate at 24 h after seeding (5 x 105 cells/well), were treated with PHMG at the concentration of 1 μg/mL, 5 μg/mL, 10 μg/mL, and 25 μg/mL, and further incubated with 40 μM of H2DCFDA (Invitrogen, CA, USA) for 1 h. At the end of H2DCFDA incubation, cells were washed with phosphate-buffered saline (PBS), and were visualized with a fluorescent microscope (Nikon, Tokyo, Japan) [14 (link)].