Erick A White1, Mark E Orazem, Annette L Bunge. 1. Department of Chemical and Biological Engineering, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, USA.
Abstract
PURPOSE: Electrochemical impedance spectroscopy is a convenient method that has been used to characterize skin barrier function, which affects drug delivery into and through the skin. The objective of this study was to relate changes in skin barrier function arising from mechanical damage to changes in the impedance spectra. These observations are compared in a companion paper to changes in chemically damaged skin. METHODS: Electrical impedance and the permeation of a non-polar compound were measured before and after human cadaver skin was damaged by needle puncture. RESULTS: The impedance responses of all skin samples were consistent with an equivalent circuit model with a resistor and constant phase element (CPE) in parallel. Pinhole-damaged skin exhibited a lower resistance pathway acting in parallel with the skin resistance without changing the CPE behavior. The characteristic frequency of the impedance scans determined after needle puncture increased by an amount that could be predicted. The flux of 4-cyanophenol increased by a small but significant amount that did not correlate with the hole resistance calculated under the assumption that the resistance of the surrounding skin did not change. CONCLUSIONS: Skin impedance measurements are sensitive to irreversible damage caused by exposure to puncture with a needle.
PURPOSE: Electrochemical impedance spectroscopy is a convenient method that has been used to characterize skin barrier function, which affects drug delivery into and through the skin. The objective of this study was to relate changes in skin barrier function arising from mechanical damage to changes in the impedance spectra. These observations are compared in a companion paper to changes in chemically damaged skin. METHODS: Electrical impedance and the permeation of a non-polar compound were measured before and after human cadaver skin was damaged by needle puncture. RESULTS: The impedance responses of all skin samples were consistent with an equivalent circuit model with a resistor and constant phase element (CPE) in parallel. Pinhole-damaged skin exhibited a lower resistance pathway acting in parallel with the skin resistance without changing the CPE behavior. The characteristic frequency of the impedance scans determined after needle puncture increased by an amount that could be predicted. The flux of 4-cyanophenol increased by a small but significant amount that did not correlate with the hole resistance calculated under the assumption that the resistance of the surrounding skin did not change. CONCLUSIONS: Skin impedance measurements are sensitive to irreversible damage caused by exposure to puncture with a needle.