Threshold Interphase Delay for Bipolar Pulses to Prevent Cancellation Phenomenon during Electrochemotherapy

Area of Science:

• Biomedical Engineering
• Cell Biology
• Electroporation

Background:

• Electroporation uses electric fields to permeabilize cell membranes, crucial for drug delivery and gene therapy.
• Nanosecond bipolar pulses in electroporation can cause a 'cancellation effect,' reducing treatment efficacy.
• The optimal temporal gap to mitigate this cancellation effect is not well-defined.

Purpose of the Study:

• To investigate the impact of interphase delay in nanosecond bipolar pulses on cell permeabilization.
• To determine the optimal delay thresholds for overcoming the cancellation effect in electroporation.
• To evaluate the influence of bipolar cancellation on in vitro electrochemotherapy outcomes.

Main Methods:

• Tested various interphase delay values (0-95 ms) with symmetric bipolar nanosecond pulses (300/500 ns) on MH-22a mouse hepatoma cells.
• Utilized 10 Hz, 100 Hz, and 1 kHz protocols to assess cell permeabilization and viability.
• Performed in vitro electrochemotherapy with cisplatin using short interphase delays (0 ms, 0.1 ms) at 10 Hz.

Main Results:

• Cell plasma membrane permeabilization and viability were characterized under different bipolar pulsed electric field protocols.
• Minimizing bipolar cancellation was achieved, yielding treatment efficiencies comparable to monophasic pulses.
• Bipolar cancellation significantly impacted cell permeabilization but had minimal effects on electrochemotherapy outcomes.

Conclusions:

• Adjusting the interphase delay in nanosecond bipolar electroporation can effectively minimize the cancellation effect.
• Optimized bipolar pulses can achieve cell permeabilization efficiencies similar to monophasic pulses.
• While bipolar cancellation affects permeabilization, its impact on electrochemotherapy efficacy is limited.