Biological Cells Response to High Power Electromagnetic Pulses

S. Xiao,^*1,2, Siqi Guo^1,2, J. T. Camp^1,2, N. Vasyl¹, A. Pakhomov¹, R. Heller¹ and K. H. Schoenbach^1,2

1) Frank Reidy Research Center for Bioelectrics, Old Dominion University, VA 23508, USA

2) Department of Electrical and Computer Engineering, Old Dominion University, VA 23508, USA

 

   The effect of high-intensity subnanosecond electric pulses and narrowband pulsed microwaves on biological cells are being explored at the Center for Bioelectrics. These pulses, either ultrawideband or narrowband, allows us to use antennas as pulse delivery systems to treat tumors inside the body noninvasivly. In our previous studies [1], it was found that subnanosecond pulses (0.8 ns) cause a significant cell death at electric fields of 150 kV/cm. However, from a practical point of view, it is very difficult to reach such high electric fields in the tissue. We have therefore focused our research on the cell response to ultrafast electrical pulses to pulse durations of 0.2 ns and less, and to electric fields of less than 50 kV/cm, which can be delivered with an Impulse Radiating Antenna (IRA). While Trypan Blue was previously used as a cell-death marker, we used patch clamp technology, single-cell diagnostics tool to study the physiological change of cell membranes. After exposure to 2000 pulses, the cell shows an increase of inward current (from the outside to the inside of the cell), whereas the outward current remains unchanged. This “rectifying” property can be due to the pores in nanometers formed across the cell membrane. Such unique characteristic was also observed in the pores created by nanosecond pulses [2]. This uni-directional transport property may allow for the calcium influx, which is useful for the activation of platelets and release of growth factors for accelerated wound healing.  

    Whereas the subnanosecond pulses primarily induce nonthermal effect, high power narrowband microwave pulses may allow us to create thermal or nonthermal effects by varying the exposure time. If the microwave power is increased, but at a decreased exposure time such that the total deposited energy is less than that used to generate hyperthermia, we can expect both electrical effects (due to the high power level), but also effects which are caused by rapid rise of heating, even if the total temperature is below the level of hyperthermia. Studying the cell death with increasing temperature rate of rise we have observed a strong nonlinear effect [3]. By increasing this rate, the death rate of liver cancer cells in suspension was found to increase with a power law. Such effect may permit a new modality for cancer treatment.

 

This research has been supported by Air Force of Scientific Research (AFOSR) and Bioelectrics Inc.

 

References:

 

[1] K. H. Schoenbach et al, “The Effect of Intense Subnanosecond Electrical Pulses on Biological Cells,” IEEE Trans. Plasma Science 36, pp. 414-424, 2008.

[2] A. Pakhomov et al, “Lipid Nanopores Can Form a Stable, Ion Channel-like Conduction Pathway in Cell Membrane,” BBRC, Volume 385, Issue 2, 24, pp.181-186, 2009.

[3] J. T. Camp, S. Xiao, H. Baldwin, and K. H. Schoenbach, “Effect of the Rate of Temperature Increase on Liver Cancer Cells in Vitro,” Power Modulator and High Voltage Conference 2010, Atlanta, GA.