Conference Contribution Details
RE Imhof, LI Ciortea P Xiao
Poster, 13th International PPP Conference, La Grande Motte, 2012.
The aim of this work was to develop a calibration method for membrane integrity measurements by the TEWL method. OECD Test Guideline 428 stipulates barrier integrity testing before permeation experiments are carried out . Tritiated water, electrical resistance and TEWL methods are recognised for such tests . In both tritiated water and electrical resistance methods the membranes under test are water-saturated. In TEWL methods, the membranes are dry on the donor side and wet on the acceptor side, a state that may be compared with normal in-vivo skin that has been acclimatised in ambient air.
The similarity of measurement conditions for in-vitro membrane integrity testing by the TEWL method and TEWL measurement on in-vivo skin should make it possible to characterise barrier function by the same measure of TEWL in-vivo and in-vitro. However, the instrumental readings cannot be compared directly, because the measurement geometries are different in the two cases. The calibration of the instrument itself is valid only for the standard in-vivo measurement geometry. For non-standard measurement geometries, an additional calibration is needed to determine a correction factor that is specific to that geometry. Such a calibration is facilitated with the AquaFlux™ TEWL instrument (Biox Systems Ltd), where purpose-designed couplings are used to maintain rigid and reproducible instrument/donor cell measurement geometries . We will describe the additional calibration method we have developed for membrane integrity testing.
Apart from the effect on flux density calibration, the different measurement geometries also affect the measurement range, ie the flux density that corresponds to zero barrier function. Both effects will be illustrated with a mathematical model of the system of membrane, Franz cell and both open-chamber and condenser-chamber TEWL measurement heads.
|1.||Skin absorption: In-vitro method.
OECD Test Guideline 428 (2004)
|2.||Guidance document for the conduct of skin absorption studies.
OECD Series on Testing and Assessment, No 28 (2004)
|3.||New developments in skin barrier measurements.
Imhof, RE, De Jesus, MEP, Xiao, P, Ciortea, LI and Berg, EP. Skin Moisturization (Editors: AV Rawlings and JJ Leyden). New York, Informa Healthcare USA: 463-479 (2009)
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