Response of Mammalian cells to non-thermal intense narrowband pulsed electric fields

This paper describes the biological effect of intense pulse electric field from the frequency point of view. A pulse-modulated sinusoidal wave as the A narrowband pulsed electric field (nbPEF) allows us to deliver a non-thermal, intense and well-defined electric field in terms of frequency, field strength and deposition energy to biological systems. 10 μs long sinusoidal electric fields with a frequency range between 0.1 and 100 MHz and field strengths of up to 10 kV/cm were applied to HeLa or HeLaS3 cells, which were subsequently analyzed in terms of the morphology and the Ca²⁺ response. The field with the frequency below a few MHz immediately causes blebs in the external field direction, whereas the morphology does not change apparently in the case of the frequency more than 10 MHz. The intracellular Ca²⁺ concentration rapidly increased after the exposure to the low frequency field and subsequently decayed exponentially within hundreds of seconds. Inversely, for the high frequency fields, the Ca²⁺ concentration did not change for seconds after the pulse, but increased gradually in tens to hundreds of seconds. When the Ca²⁺ channel on the plasma membrane was inhibited, the delayed Ca²⁺ uptake was suppressed. Our experiment shows that the possibility to activate or impair function of membrane proteins physically by using nbPEF without significant defects of the plasma membrane.