Fig 1. Effects of THz irradiation on cell morphology.

(A) Schematic illustration of the experimental setup. THz waves with a power density of 0.6 W/cm², frequency of 0.46 THz, pulse duration of 10 ms, and a repetition rate of 1 Hz were generated by a gyrotron at FIR-UF. The THz beam passed vertically from the bottom of the dish via an aperture of 4 mm in the heating stage. As a second source of THz irradiation, we used a IMPATT-diode which ensured coherent continuous-wave emission of THz waves with a frequency of 0.28 THz and output power of 20 mW. THz radiation was outputted from the horn antenna with a power density of 125 mW/cm². HeLa cells were seeded on the film bottom dish and cultured for 24 hours before the experiments. The culture medium was kept at 37 °C by the heating stage during the experiments. (B) Microscopy images of cells at 0, 30, and 60 minutes. Irradiation was started at 0 minutes and continued for 60 minutes. The bottom panels show the magnified images of the black squares in the upper panels. The red arrows indicate a pair of cells with a round shape. The scale bar represents 200 μm (upper panel) and 20 μm (bottom panel).