Localization of conductive pathways in human stratum corneum by scanning electrochemical microscopy

The location of conductive pathways for small ions in human stratum corneum under iontophoretic conditions was investigated by scanning electrochemical microscopy (SECM), An experimental setup for SECM with a manual scanning system was assembled. Platinum microelectrodes in a glass insulator (total diametr of 25 mu m, diameter of the active zone from 4 mu m to 20 mu m) were used. Different model films and human skin samples have been studied, The electrode current maxima were registered for Teflon films (thickness of 50 mu m) with 1-2 macropores (diameter of 200 mu m). An uniform level of the electrode current was observed for Terilen films (thickness of 20 pm) with high density of small micropores (diameter of 0.1 mu m). The current maximum was found in experiments with human skin samples, That was located near an exit of a hair fillicle. The macropore radius was determined by comparison of the experimental data with the theoretical calculation band on the model of the diffusion from a planar disk. The determined macropore radius was 9.2-14.1 mu m that is in a good agreement with morphological data.