Characterization of damaged skin by impedance spectroscopy: chemical damage by dimethyl sulfoxide.

Purpose: To relate changes in the electrochemical impedance spectra to the progression and mechanism of skin damage arising from exposure to dimethyl sulfoxide (DMSO).

Methods: Electrochemical impedance spectra measured before and after human cadaver skin was treated with neat DMSO or phosphate buffered saline (control) for 1 h or less were compared with electrical circuit models representing two contrasting theories describing the progression of DMSO damage. Flux of a model lipophilic compound (p-chloronitrobenzene) was also measured.

Characterization of damaged skin by impedance spectroscopy: mechanical damage.

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.

On the correlation between single-frequency impedance measurements and human skin permeability to water.

The objective of this study was to quantitatively compare measurements of tritiated water permeability with impedance determined at either 100 or 1000 Hz using an LCR databridge on the same pieces of skin. A previously published expression based on a simple circuit of a parallel resistor and constant phase element (CPE) was used to relate (RPARA) measured at different frequencies to the DC resistance (RskinA) and the steady-state skin permeability of tritiated water (kp). Using this analysis, kp and (RPARA) data from three laboratories were shown to be consistent with each other, and kp and (RskinA) estimated from (RPARA) were linearly correlated.

A critical analysis of single-frequency LCR databridge impedance measurements of human skin.

Testing whether the barrier of skin samples has sufficient integrity for meaningful measurements of in-vitro chemical permeability is usually required when data are generated for regulatory purposes. Recently, skin integrity has been assessed using LCR databridge measurements, which are reported as resistances determined in either series (SER) or parallel (PAR) modes at a single frequency, typically 100 or 1000Hz. Measurements made at different combinations of mode and frequency are known to differ, although the skin literature reveals confusion over the meaning of these differences and the impact on the interpretation of integrity test results.