Intracellular DNA breakage in CHO cells induced by exposure to intense burst sinusoidal electric fields

Intracellular DNA breakage induced by exposing to non-thermal, intense burst sinusoidal electric fields (IBSEF) was studied by means of alkaline comet assay, single cell electrophoresis. The IBSEFs with frequency in the range of 300 kHz-100 MHz and with field strength up to 200 kV/m were applied to cultured Chinese hamster ovary (CHO) cells. The DNA breakage indicated by the comet pattern was evaluated by using Olive Moment Method. The experiment shows that the DNA breakage depends both on the field strength and on the frequency of the IBSEF. For the frequency of 100 MHz, the critical field strength is 10 kV/m. For the strength of 100 kV/m, the DNA is damaged only with the frequency exceeding 1 MHz. Two dimensional calculation of the electric field distribution under an alternating field implies that the DNA breakage occurs only when the intracellular electric field exceeds 30 kV/m, which might trigger biological processes leading to the DNA breakage.