Electroporation of human skin: Simultaneous measurement of changes
in the transport of two fluorescent molecules and in the passive electrical
Pliquett U, Weaver JC Bioelectrochemistry and Bioenergetics 39: (1) 1-12 FEB 1996
The stratum corneum (SC) of mammalian skin is a formidable barrier to the
transport of both small ions and charged molecules, but large, very rapid
increases in transport can be created by ''high-voltage'' pulses. Here a
series of exponential pulses (tau(pulse) = 1.1 ms) was used in vitro with
human skin preparations. A flow-through apparatus provided simultaneous,
continuous measurements for the transport of two fluorescent molecules
(calcein, 623 Da, charge of z(cal) = -4; sulforhodamine, 607 Da, charge
of z(sr) = -1) and the skin's passive electrical properties, with emphasis
on the transdermal conductive behavior, which includes both the d.c.
conductance, G(skin), and the non-linear dynamic conductance, G(dy).
''High-voltage'' pulsing was found to cause large and very rapid changes
in the molecular flux of both molecules, and also in G(skin) and G(dy).
In the case of molecular transport, the relative contribution of local
diffusion and local electric field-driven transport depends significantly
on the molecular charge, z(s). The field-driven transport during a pulse
allowed estimates of the maximum fractional aqueous area, F-w,F-s, of the
skin that was transiently available during a pulse for small ions
(F-w,F-ions = 6 +/- 3 X 10(-4)), calcein (F-w,(cal) = 5 +/- 3 X 10(-5)),
and sulforhodamine (F-w,F-sr = 7 +/- 4 X 10(-5)). Comparison of the
post-pulse recovery of G(skin) and the decrease of the molecular transport
showed that the recovery of the skin barrier and molecular flux decay
are not identical. These results are interpreted as being due to electrical
creation of new aqueous pathways (''pores'') across the lipid regions
of the skin's stratum corneum, and support the hypothesis that
electroporation is responsible for the rapid and large changes observed.