Electroporation
Electroporation
is a temporary condition of the outer membrane of blood cells becoming
"porous" as a result of high electric fields causing 1/2 to 1 volt
across each of the cells. While the cells are porous, normally unwanted
fluid & substances can enter into the blood cell with resultant
disturbing effects. This man-made effect is useful to scientists
though, which is why there are companies like Genetronics which
manufacture laboratory instruments which induce electroporation. It
should be a great relief to all to know that these blood
electrification devices do not produce an effect so extreme as
electroporation. Brian Austin, Technical Support Manager at Genetronics
(an electroporation device company), emailed me concerning Beck blood
electrifiers that "with the (electrical) conditions used, there should
be no electroporation effects. Field strengths are not high enough." J.
C. Weaver of the Massachusetts Institute of Technology in his report on
electroporation published in the Journal of Cellular Biochemistry
(51:426-435 1993) reported "In the case of isolated cells, mammalian
cells experience electroporation for electric fields of about E=1kv/cm
(1000 volts with a distance of 1 centimeter between electrodes) for
short pulses." Another electroporation device manufacturer, Cyto Pulse
Sciences, stated on their website (in the equipment tutorial) that red
blood cells need 1430 volts per centimeter for electroporation. The
research paper "Microfluidic electroporation of tumor and blood cells:
observation of nucleus expansion and implications on selective analysis
and purging of circulating tumor cells"
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2872780/ stated that
"With the electroporation duration of 100–300 ms, the threshold for
irreversible electroporation (or electric lysis) is ~300–100 V/cm-1 for
M109 tumor cells and ~ 1100–1200 V/cm-1 for RBCs [red blood cells].
WBCs [white blood cells] presented a low threshold of 400–500 V/cm-1."
[V/cm-1 refers to the voltage per .1cm electrode spacing which is per
millimeter. 300ms equals .3 seconds. This is the maximum exposure to
electricity they use because otherwise the electricity would overheat
the cells if more time was used.]
Typically, 10,000-100,000 V/cm (varying with cell size) in a pulse
lasting a few microseconds to a millisecond is necessary for
electroporation. This electric pulse disturbs the phospholipid bilayer
of the membrane and causes the formation of temporary aqueous pores.
The electric potential across the membrane of the cell simultaneously
rises by about 0.5-1.0 volts so that charged molecules (such as DNA)
are driven across the membrane through the pores in a manner similar to
electrophoresis.
http://www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2003/McCord/electroporation.htm
Wikipedia on electroporation: "It is generally accepted that for a
given pulse duration and shape, a specific transmembrane voltage
threshold exists for the manifestation of the electroporation
phenomenon (from 0.5 V to 1 V)."
"Transmembrane", in context of talking about a cell, means "across the
cell membrane" which basically means from one side of the cell to the
other. So when the electroporation papers say around 1 volt
transmembrane voltage is needed they are saying each cell in a culture
needs that voltage. Let's say the cell culture has a cell density that
provides 1,000 cells linearly between the electroporators electrodes.
1,000 volts would need to be provided to produce 1v transmembrane
voltage.
Wikipedia, on "red blood cell", says "women have about 4 to 5 million
per microliter (cubic millimeter) of blood and men about 5 to 6
million". That gives a linear density of almost 170. (What I mean is
that there would be 170 cells in one line from one side to the other of
that cubic millimeter.) From hand to hand the arteries have a distance
around 1600 millimeters. So the linear density of red blood cells from
hand to hand is 1600x170 which is 272,000. Applying 30 volts from an
electromedicine device means each red blood cell will have 30/272,000
volts which is .00011 volts each. This is about 10,000 times too weak
to cause electroporation.
http://medical-dictionary.thefreedictionary.com/electroporation
"electroporation: the use of high-voltage electrical impulse to
create pores through a cell membrane and allow uptake of DNA into a
cell."
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