Conference Contribution Details


RE Imhof, P Xiao and LI Ciortea
Podium Presentation, ISBS International Congress, Besançon 2009.



The aim of this work is to develop an improved understanding of how stratum corneum (SC) properties of hydration, TEWL and swelling are affected by ambient conditions of temperature and humidity. The method used is to calculate the steady-state flux of water diffusing from the viable epidermis, through the SC, into the ambient air. The SC is modelled on a macro-scale, where the bricks & mortar structure, tortuosity and other micro-scale properties are subsumed into an effective diffusion coefficient. The effect of water binding in the SC is represented by a hydration-dependent effective diffusion coefficient. The interaction between the SC surface and the adjacent air is described by a sorption isotherm. SC swelling is assumed to be isotropic and additive, where the volume of hydrated SC is given by the sum of the volumes of dry SC and water of hydration.

We will present results of calculations using both constant and hydration-dependent diffusion coefficients, with and without swelling. Calculated hydration depth profiles will be compared with those measured using confocal Raman spectroscopy. Also presented will be calculations of the dependence of TEWL and SC thickness on ambient temperature and RH, again comparing these with published measurements.

Work is in progress to extend the model to include calculations of changes of TEWL with thickness of SC removed in tape stripping experiments and time-dependent changes of TEWL and hydration when steady-state conditions are perturbed.


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