PURPOSE: To study ion transport through stratum corneum (SC) lipid lamellae under passive and iontophoretic conditions. METHODS: Iodide ion transport was measured by fluorescence quenching. Since the process involves diffusion of an iodide ion to the fluorophore located within the SC lamellae, the accessibility of iodide ions was measured. Moreover, the use of anthroyloxy fatty acid probes, provided information as a function of depth within the lamellae. RESULTS: Fluorescence quenching by iodide ions increased with iontophoretic current density, suggesting increased ion accessibility within the SC lamellae. In addition, at constant current, quenching decreased as the fluorophore was located deeper within the lamellae. This gradient in ion accessibility suggests that more iodide is found near the head-group than near the core of the SC lipid lamellae. Results obtained in the absence of iodide also show increased water accessibility during iontophoresis. CONCLUSIONS: These results show that in the presence of an applied electric field the SC lipid lamellae interior becomes more accessible to water and ions. These results imply that during iontophoresis, ion and water transport through human skin is associated, at least in part, with the SC lipid lamellae.
PURPOSE: To study ion transport through stratum corneum (SC) lipid lamellae under passive and iontophoretic conditions. METHODS:Iodide ion transport was measured by fluorescence quenching. Since the process involves diffusion of an iodide ion to the fluorophore located within the SC lamellae, the accessibility of iodide ions was measured. Moreover, the use of anthroyloxy fatty acid probes, provided information as a function of depth within the lamellae. RESULTS: Fluorescence quenching by iodide ions increased with iontophoretic current density, suggesting increased ion accessibility within the SC lamellae. In addition, at constant current, quenching decreased as the fluorophore was located deeper within the lamellae. This gradient in ion accessibility suggests that more iodide is found near the head-group than near the core of the SC lipid lamellae. Results obtained in the absence of iodide also show increased water accessibility during iontophoresis. CONCLUSIONS: These results show that in the presence of an applied electric field the SC lipid lamellae interior becomes more accessible to water and ions. These results imply that during iontophoresis, ion and water transport through human skin is associated, at least in part, with the SC lipid lamellae.