2.7. Live/dead cell staining assay

HCT116 cells were seeded in 6-well plates at a density of 5 × 10⁵ cells per well. After 24 h plating, the cells were incubated with (1) 0, 5 and 10 mg/L VER-M at 37 °C; (2) 0, 5 and 10 mg/L VER-M at 40 °C; (3) 0, 5 and 10 mg/L VER-M containing 50 mg/L MPEG-AuNR with 808 nm Laser (2.5 W/cm², 4 min to 45 °C) after being incubated for 2 h; (4) 0, 5 and 10 mg/L VER-M containing 50 mg/L MPEG-AuNR with 808 nm Laser (3 W/cm², 4 min to 55 °C), respectively. After incubation for 2 h, the cells were washed 3 times with PBS, and 200 mL working solution (PBS containing 2 μmol/L calcein AM, 8 μmol/L PI) were added and the cells were further incubated for 30 min at room temperature away from light. Finally, the cells were washed 3 times with PBS again, and observed under fluorescent microscopy.