Irreversible electroporation and apoptosis in human liver cancer cells induced by nanosecond electric pulses

The goal of this study was to assess the effect of nanosecond electric pulses on HepG2 human liver cancer cells. Electric pulses with a high strength of 10 kV/cm, duration of 500 ns and frequency of 1 Hz were applied to the cells. After delivery of electric pulses, apoptosis, intracellular calcium ion concentrations, transmembrane mitochondrial potentials, electropermeabilization and recovery from electropermeabilization in cells were investigated. The results showed that electric pulse treatment for 20 s and more could trigger apoptosis in cells. Real-time observation indicated an immediate increase in intracellular calcium ion concentration and a dramatic decrease in mitochondrial membrane potential in cells responding to electric pulses. In subsequent experiments, propidium iodide uptake in cells emerged after exposure to electric pulses, indicating electropermeabilization of the cell membrane. Furthermore, recovery from electropermeabilization was not observed even 4 h after the stimulation, demonstrating that irreversible electropermeabilization was induced by electric pulses. In conclusion, electric pulses with a high strength and nanosecond duration can damage cancer cells, accompanied by a series of intracellular changes, providing strong evidence for the application of electric pulses in cancer treatment.