Does the shape of the electric pulse matter in electroporation?

Abstract

Electric pulses are widely used in biology, medicine, industry, and food processing. Numerous studies indicate that electroporation (EP) is a pulse-dependent process, and the electric pulse shape and duration strongly determine permeabilization efficacy. EP protocols are precisely planned in terms of the size and charge of the molecules, which will be delivered to the cell. In reversible and irreversible EP applications, rectangular or sine, polar or bipolar pulses are commonly used. The usage of pulses of the asymmetric shape is still limited to high voltage and low voltage (HV/LV) sequences in the context of gene delivery, while EP-based applications of ultra-short asymmetric pulses are just starting to emerge. This review emphasizes the importance and role of the pulse shape for membrane permeabilization by EP.

Keywords: electric pulse; electroporation; permeabilization; pulse frequency; pulse shape.

Figure 1

The exponential decay (A) and square wave (B) pulse waveforms, where t_th is the time when the amplitude drop below the electric field value required for electroporation (E_th).

Figure 2

An example of typical transient processes occurrent in electroporation systems during pulse delivery, where t_r is the pulse rise time and RLC is the resistor/inductor/capacitor circuit.

Figure 3

An example of the typical influence of the load impedance on pulse shape.

Figure 4

Overview of the CANCAN effect. (A) Summation of the bipolar pulses results in the formation of a unipolar pulse with the resultant pulse in Phase 1. (B) Two arrangements of electrodes for the study of the CANCAN effect and the effects of pulsation in each of the phases. The left side shows the linear arrangement of the needle electrodes; on the right side, the needle electrodes are arranged in a square—in each case, the distance between the neighboring needles remains constant.

Figure 5

The examples of asymmetric and symmetric waveforms.