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Published online by Cambridge University Press: 02 July 2020
Electroporation has been used to permeabilize the skin to enhance the transdermal delivery of molecules. The mechanism is generally believed to be based on the temporary breakdown and permeabilization of the stratum corneum by the applied pulsed electric field. The kinetics of recovery are believed to be in the millisecond range. However, no structural changes within this time scale have been observed.
We studied the morphological changes to heat stripped porcine stratum corneum following an electroporating pulse by time-resolved freeze fracture electron microscopy. Pulses at a supraelectroporation threshold of 80 volts and 300 μsec were applied across the stratum corneum with a pair of copper plate electrodes, which also served as cooling contacts. The pulse timing was accomplished through the time-of-flight of a trigger bar attached to the plunging rod holding the sample.. The trigger bar passes through two optical switches. As the sample was propelled towards the liquid propane coolant container, the first switch triggered the pulse generator and the second marked the precise time at which the sample was frozen. The sample was pulsed at set times of 0.5 ms, 12ms, 5 sec, 60 sec, and 300 sec before freezing.