Search

Intracellular DNA damages caused by intense burst sinusoidal electric fields (IBSEFs) were investigated by means of an alkaline comet assay method. Non-thermal, 200 μs-long IBSEF with various frequency values (300 kHz-100MHz) and strengths (up to 200 kV/m) was applied to Chinese hamster ovary (CHO) cells in a suspending medium between 1 mm gap parallel electrodes. The comet assay suggests that 100 kV/m IBSEF with frequencies exceeding 1 MHz or 100 MHz IBSEFs with field strengths exceeding 3 kV/m induces significant DNA damage. According to the numerical calculation of the electric field over a simplified cell model under an alternating electric field, the intracellular field strength increases with increasing alternating frequency. The minimum level of the field strength that induces the DNA damage is in the range of 10-30 kV/m. This intracellular strong field might trigger biological processes leading to the DNA damage. [ABSTRACT FROM AUTHOR]

This paper describes the biological response of cultured HeLa S3 cells to non-thermal, intense burst sinusoidal electric fields (IBSEF). The proliferation activity of the cells subjected to 300 kV/m, 200 μs-long IBSEF with a frequency between 0.3 MHz and 100 MHz was evaluated by using an automatic cell event monitor, xCELLigence, for 48 hours. The experiment showed that the cell proliferation depended on the pulse number and the frequency band of the IBSEF. The application of the smaller number of the pulses enhances the proliferation, whereas the large number of pulses tends to kill the cells. The dependence on the pulse number indicates the effect of the pulse is accumulated. The cells seem to be more sensitive to the pulses at the lower frequencies less than 1 MHz. The frequency of 100 MHz, which is sufficiently large for the field to penetrate into the cell, did not appear to influence the proliferation and the immediate death process. When the cells were subjected to 30 pulses of 3 MHz IBSEF, the proliferation was promoted 1.6 times as fast as that of the sham exposure. The frequency dependence of the proliferation might be associated with the electrical stress at the plasma membrane where several proteins related to the cell cycling are located. [ABSTRACT FROM PUBLISHER]