Conference Contribution Details
RE Imhof, P Xiao, EP Berg & LI Ciortea.
Contributed Talk, US Symposium of the International Society for Biophysics and Skin Imaging, Atlanta, October 2006.
Barrier integrity assessment using a physical technique such as TEWL or TER (Transcutaneous Electrical Resistance) is an integral part of experimental protocols for in-vitro dermal absorption measurements. The aim of the present study was to assess the performance of a condenser-chamber TEWL instrument for this task.
The experiments used an AquaFlux™ Model AF103 TEWL instrument (Biox Systems Ltd, UK) with a 9mm PermeGear Franz Diffusion Cell (PermeGear Inc, USA). A push-fit coupling between the TEWL measurement head and the Franz cell donor chamber was developed, to give a vapour-tight seal without the need to touch the membrane under test.
Initial experiments used Sil-Tec membranes (Technical Products Inc, USA), whose well controlled properties could be relied upon to verify the measurements. Subsequently the system was used to characterise samples of snake skin sheddings as more realistic examples of the kinds of bio-membranes that could be used in dermal absorption measurements in practice.
The data analysis method uses Fick’s first law to calculate membrane diffusion resistance from steady-state TEWL flux measurements. The method was verified with the Sil-Tec measurements, where diffusion resistance was found to correlate linearly with thickness with a Pierce Correlation Coefficient of 0.9998 (P<0.0001).
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