Membrane Electroporation Biophysics
Cell membranes are made up of a phospholipid bilayer that behave as a
2-dimensional aqueous solution and serve as a barrier to polar
molecules. This stable structure protects the cell from its environment
and is integral to the cell’s function and survival. However, the
stability of the phospholipid bilayer is reduced when exposed to
external electric fields and leads to the formation of nanopores, which
can allow transfer of ionic particles between the external environment
and cell interior, known as electroporation. The lifetime of nanopores
can range from milliseconds to minutes after the electric field is
removed and is related to the electric field strength and duration (12).
The cell may remain viable if the cell membrane recovery is rapid,
termed reversible electroporation. However, if pores formed in the cell
membrane are sufficient in number or have a long lifetime, this may lead
to irreversible pore formation and cell death, termed irreversible
electroporation (13).
Myocardial cells are uniquely sensitive to high voltage, short duration
electric fields with electroporation thresholds of 268-375 V/cm compared
to other tissue types including nerves, endothelium, smooth muscle
(i.e., vessels, esophagus), and blood cells, all of which have
electroporation thresholds of greater than 1600V/cm (figure 1) (14-18).
However, these thresholds were evaluated with different experimental
designs, and they may not be applicable with different pulse waveforms
and electrode configurations. Furthermore, the threshold of reversible
electroporation has not been well defined.