Intracellular DNA Damage Induced by Intense Burst Sinusoidal Electric Fields

Non-thermal, intense electric fields with frequencies exceeding 1 MHz are known to cause intracellular effects to mammalian cells. In this paper, intracellular DNA break induced by an intense burst sinusoidal electric field (IBSEF) are investigated by means of the alkaline comet assay. The 200 μs long, 100 MHz IBSEF with the amplitude up to 200 kV/m was applied to Chinese hamster ovary (CHO) cells. The application of the IBSEF gives non-thermal effects to CHO cells since the temperature rise owing to Joule heating in this study is at most 1.2 oC, which is considered to be sufficiently small to influence the biological activity. Degree of the DNA break was evaluated by the tail extent of the comet pattern. It has been experimentally shown that the application of the IBSEF with the amplitude more than 100 kV/m induces a significant damage to the intracellular DNA. The comet pattern of the cells subjected to the IBSEF are different from that of the cells exposed to an ultraviolet radiation (312 nm), whereas their comet extents are the same level. The difference in the comet pattern implies that the DNA damage process by the IBSEF application might be different from that of ultraviolet irradiation.