A theoretical study of outermost skin layer electroporation.

Two models of electrohydration of stratum corneum (SC) have been developed. In the first model, the hydration of one interbilayer region is considered on the assumption that water molecules are adsorbed on the inhomogeneous surface of a bilayer and can interact, thereby lowering their energy on the surface. The dependence of the hydration degree on the voltage across the skin had been found. At certain parameter values the degree of hydration rapidly grows at certain voltage up to the magnitudes at which continuous water pathways appear. The second model has used the macroscopic approach which presumes water to be present in the interbilayer region as microdrops. The dependence of the hydration degree on voltage has been also found. At voltages of the order of tens of volts the obtained hydrations of interbilayer regions are sufficient to generate electroinduced hydrophilic pores in the SC lipid phase. Formation of tortuous continuous pathways for the transport of small ions is little probable because it requires voltages much higher than 100 V. We suggest that small ions pass the skin by the straight way through corneocytes and lipid bilayers at voltages of the order of tens of volts and higher.