Exploring the Depths of Percutaneous Penetration

By: Elsa Jungman, Université Paris-Sud

Posted: July 3, 2012

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The official conference opened with a presentation from Tom Franz, the inventor of Franz cells, who discussed the use of in vitro permeation as a bioequivalence tool. He talked about the correlation between in vivo and in vitro data and, from the literature, showed that data from studies conducted with fully harmonized protocols could be totally correlated to in vivo data. Pauls Matts, PhD, of Procter & Gamble, then spoke on the effects of an aqueous British Pharmacoepia-registered (BP) cream on eczema. Such an aqueous cream (AQC) is a light, paraffin-based emulsion that is categorized by the British National Formulary as non-proprietary emollient preparation. It contains the anionic surfactant sodium lauryl sulfate (SLS). However, the recommendation for using AQC as an emollient in atopic skin is surprising, as SLS is a known skin irritant.

Matts described an experiment wherein AQC was applied for one month on the volar forearm of skin. Results showed an increase in desquamatory and inflammatory protease activity, and changes in corneocyte maturity and size, which are also indicative of accelerated skin turnover induced by chronic application of this emollient. These findings question the routine prescription of this preparation as a moisturizer in patients with atopic dermatitis.

Johanna Brandner, PhD, of the University of Hamburg, explained the role of tight junction assembly in the barrier function. Tight junctions, cell-cell junctions localized in the stratum granulosum, are a barrier for ions, water and macromolecules, especially claudine-1. Brandner showed that a decrease of this protein would increase the TEWL, and that an alteration of the tight junction in the epidermis leads to skin diseases such as psoriasis, ichthyosis and atopic dermatitis. The next step would be to study the role of these proteins in exogenous molecule penetration.

Peter Caspers, PhD, of Erasmus MC & River Diagnosis, presented a Raman spectroscopy method to rapidly determine the natural moisturizing factor (NMF) in the stratum corneum of adults and young babies. The new protocols presented offer a direct and non-invasive method to determine early in infants whether there is a deficiency of NMF that could lead to atopic skin.

Cosmeceuticals

The second day opened with two talks on cosmeceuticals. Randy Wickett, PhD, of the University of Cincinnati, and Chris Gummer, PhD, of Cider Solutions Ltd., presented their viewpoints on cosmeceuticals. For Wickett, cosmeceuticals have no legal definition. Cosmeceutical is a term used to describe active cosmetics that have a positive effect on skin beyond cleaning and moisturizing. According to Wickett, the most common cosmeceuticals are retinol, antioxidants, niaciamide, natural anti-aging peptides, etc. All of these compounds aim to decrease fine lines and wrinkles.