Kinetics of the temperature rise within human stratum corneum during electroporation and pulsed high-voltage iontophoresis.

Electroporation is believed to be a nonthermal phenomenon at the membrane level. However, the effects of associated processes, such as Joule heating, should be considered. Because electroporation of skin, specifically the stratum corneum (SC), occurs at highly localized sites, the heating is expected to conform locally to the sites of electroporation. Significant localized heating was found to be strongly dependent on the voltage and duration of the high-voltage pulses. Specifically, a localized temperature rise was predicted theoretically and confirmed by experiments, with only a small rise (about 17 degrees C) for short, large pulses (1 ms, 100 V across the SC), but was increased (about 54 degrees C) for long, large pulses (300 ms, 60 V across the SC). The latter case appears to result in irreversible structural changes like vesicularization of the lipid lattice. These results support the hypothesis that electroporation occurs within the SC and that additional processes, such as localized heating, may be important.