In-vitro bipolar nano- and microsecond electro-pulse bursts for irreversible electroporation therapies

摘要

Under the influence of external electric fields, cells experience a rapid potential buildup across the cell membrane. Above a critical threshold of electric field strength, permanent cell damage can occur, resulting in cell death. Typical investigations of electroporation effects focus on two distinct regimes. The first uses sub-microsecond duration, high field strength pulses while the second uses longer (50 μs+) duration, but lower field strength pulses. Here we investigate the effects of pulses between these two extremes. The charging behavior of the cellmembrane and nuclear envelope is evaluated numerically in response to bipolar pulses between 250 ns and 50 μs. Typical irreversible electroporation protocols expose cells to 90monopolar pulses, each 100 μs in duration with a 1 second inter-pulse delay. Here, we replace each monopolar waveform with a burst of alternating polarity pulses, while keeping the total energized time (100 μs), burst number (80), and inter-burst delay (1 s) the same.We show that these bursts result in instantaneous and delayed cell deathmechanisms and that there exists an inverse relationship between pulse-width and toxicity despite the delivery of equal quantities of energy. At 1500 V/cm only treatments with bursts containing 50 μs pulses (2×) resulted in viability below10%. At 4000 V/cm, burstswith 1 μs (100×),2μs (50×), 5 μs (20×),10μs (10×),and50μs (2×) duration pulses reduced viability below10%while burstswith 500 ns (200×) and 250 ns (400×) pulses resulted in viabilities of 31% and 92%, respectively.