Introduction
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1
Chapter 1
Introduction
Electroporation is commonly used for delivering macromolecules, including DNA,
RNA, dyes, and proteins, into cells. Electroporation involves two basic
components, the permeabilization of cell membranes by application of short-
duration electric field pulses, and electrophoretic delivery of molecules through
these pores (Kinosita, 1979; Weaver, 1993; Neumann
et al
., 1999; Ho
et al
., 1996).
When cells are placed in an electric field, charged ions within the cells migrate
towards the external electrodes, resulting in a build-up of charge at the poles of the
cells adjacent to the oppositely-charged extracellular electrodes. When the induced
transmembrane potential reaches approximately 0.25 V to 1 V, the electrostatic
forces holding the lipid bilayer together break down, causing a reconfiguration of
the membrane phospholipids and creation of minute pores in the small regions of
the membrane at each pole (Neumann
et al
., 1999; Ho
et al
., 1996). Once formed,
these pores (20 nm to 120 nm in diameter) remain open even after the external
electric field is removed. Molecules from the extracellular solution move into the
cell soma through these pores. Charged molecules in the extracellular solution
migrate towards the electrode of the opposite charge. Uncharged molecules will
follow the concentration gradient. When the electric field terminates, small pores
eventually collapse and the cell membrane continuity recovers over a timescale of
tens to hundreds of milliseconds trapping the molecules that have moved across the
Introduction
