58

Bioelectromagnetism

Te earliest observations of phenomena similar to irreversible electroporation could be back to the

1700s. Irreversible electroporation may have been observed in 1754 when Abbè Nollet studied the dis­

charge of static electricity. Using this discharge, he applied an electric spark to human and animal skin.

He reported the formation of red spot on the spark-applied areas. Tese can be explained as damage

to the capillaries by irreversible electroporation (Vanbever and Prèat 1999). In the 1800s, high volt­

age discharge had been used in order to purify river water (Deipolyi et al., 2014). In 1898, Alphonso

David Rockwell (1840–1933), an American electrotherapist, found that Under the discharges of the

Leyden jar the red corpuscles change their shape and lose their color. Tis may be homolysis induced

by irreversible electroporation (Rockwell, 1903). In 1954, Stämpfi published the frst report about the

breakdown of the plasma membrane by the direct application of a high intensity electric feld (Stämpfi,

1954). Stämpfi reported of electroporation-related phenomena, the irreversible and reversible of break­

down of the excitable membrane of Ranvier node of frog (Stämpfi, 1957; Stämpfi and Willi, 1957). He

reported that membrane breakdown is irreversible under certain conditions, whereas in other cases, it

is reversible, and he compared this breakdown phenomenon to that of a dielectric/capacitor. In 1956,

Bernhard Frankenhaeuser (1915–1994) and Lennart Widén, both at the Karolinska Institute, Stockholm,

attempted to explain the change in normal nerve conductivity behavior. Tis change was anode break

excitation when electric pulses are applied on nerve nodes. Te authors stated that

in experiments with bipolar stimulation of the desheathed nerve, with both stimulating electrodes

well away from the cut ends of the fbres, it was found that stimuli from threshold strength to about

ten times threshold strength with durations from less than 1 ms to more than 100 ms elicited a

discharge in the nerve at make but not at break.

Frankenhaeuser and Widén (1956)

J. H. Sale and W. Allan Hamilton, from the Unilever Research Laboratory and University of Aberdeen,

Scotland, published three seminal papers which became the basis of irreversible electroporation (Hamilton

and Sale, 1967; Sale and Hamilton, 1967a, b). Tey reported in the frst paper the non-thermal efects of high

DC pulsed electric feld on killing the bacteria (inactivation of microorganisms). Tey exposed vegetative

bacterial and yeast preparations (Escherichia coli, Staphylococcus aureus, etc.) to DC pulsed electric felds

of 25–30 kV/cm. Te evaluation was that the non-thermal bactericidal efect was to minimize the tempera­

ture rise. In this experiment, very short pulses between 2 and 20 μs at several second intervals were used.

In the second paper (1967a), they tried to elucidate what is the mechanism by which the high DC pulsed

electric feld kills the cells. Teir conclusion was that the irreversible loss of the membrane’s function as a

semipermeable barrier was the cause of cell death. In the last and third paper (1967b), they suggested that

the transmembrane potential induced by the external feld may cause “conformational changes in the

membrane structure resulting in the observed loss of its semipermeable properties.” Tey concluded that

the cell membrane is damaged when transmembrane voltages of around 1 V are reached.

In the 1970s and 1980s, key research studies brought the reversible electroporation into the feld of

biotechnology and medicine, and they focused on the fundamental understanding of the mechanisms

involved. Eberhard Neumann, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany,

and Kurt Rosenheck, professor at Te Weizmann Institute of Science, Rehovot, Israel, investigated the

reversible electroporation of cell membranes in 1972 (Neumann and Rosenheck, 1972). Tey used pulsed

electric felds of about 18–24 kV/cm with about 150 μs duration and showed the production of the revers­

ible permeabilization of the cell membrane of bovine adrenal medullary chromafn granule cells as a

vesicular model system. Te main soluble constituents of these vesicles are catecholamines (CA; epi­

nephrine (E), norepinephrine (NE)), ATP, and proteins. Release of part of the CA and ATP content

from the isolated granules of the bovine medulla occurred readily at higher temperatures. Temperature

increase accompanying the electric impulse was smaller than 6°C. Te impulse-induced release of CA

and ATP was non-thermal (Neumann and Rosenheck, 1972). Tis paper triggered many research groups

to begin the study of electroporation.