Comparison of the effects of the repetition rate between microsecond and nanosecond. pulses: Electropermeabilization-induced electro-desensitization?

Background: Applications of cell electropermeabilization are rapidly growing but basic concepts are still unclear. In particular, the impact of electric pulse repetition rate in the efficiency of permeabilization has not yet been understood. Methods: The impact of electric pulse repetition rate in the efficiency of permeabilization was analyzed in experiments performed on potato tissue and partially transposed on mice liver. On potato tissue, pulses with durations of 100 mu s or 10 ns are applied. The intensity of permeabilization was quantified by means of bioimpedance changes and electric current measurements and a new index was defined. Results: For the two pulse durations tested, very low repetition rates (below 0.1 Hz) are much more efficient to achieve cell permeabilization in potato tissue. In mice liver, using 100 mu s pulses, the influence of the repetition rate is more complex. Indeed, repetition rates of 1 Hz and 10 Hz are more efficient than 100 Hz or 1 kHz, but not the repetition rate of 0.1 Hz for which there is an impact of the living mice organism response. Conclusions: We propose that the effects reported here might be caused by an electroporation-induced cell membrane 'electro-desensitization' which requires seconds to dissipate due to membrane resealing. General significance: This study not only reinforces previous observations, but moreover it sustains a new concept of 'electro-desensitization' which is the first unifying mechanism enabling to explain all the results obtained until now both in vitro and in vivo, with long and short pulses. (C) 2014 Elsevier B.V. All rights reserved.