Skin

Project outline

Why model skin?

The skin provides the barrier function for the body, stopping things getting into our bodies, and internal fluids from escaping. For many situations this is a good thing. In everyday situations many contaminants may come into contact with our hands, but we wouldn't want them getting into our blood stream. Alternatively, there are certain benefits for being able to breach this barrier: perhaps the most common being the topical application of drug delivery patches, such as nicotine patches. The ability to deliver enough chemical through the skin is limited by the size of the molecules in question, and hence relatively few drugs can be delivered transdermally.

The skin itself has several different layers. My research is only interested in the very top layer, the stratum corneum. This is the layer responsible for not letting the water in as it is highly hydrophobic and lipophilic. It also provides almost all of the barrier function of the body. Perhaps contrary to our expectations, the pores and sweat glands contribute very little in terms of routes into the body. They cover less than 1% of the total skin surface and are not a noticeable delivery route.

The stratum corneum is a complex structure. It is formed of planes of tesselating hexagonal corneoctes stacked upon one another, with the intercellular spaces filled with lipid. This lipid forms the drug delivery route, as the corneocytes are assumed to be virtually impermeable. The spacing in real skin means that a very tortuous path is taken by diffusing chemical as it winds between the corneocytes. In reality the corneocytes are of the order 40 micrometres across, a height of 1 micrometre, and lipid width of 0.1 micrometres.

In the following pictures we represent external geometry only, coloured by the solution concentration from magenta being high concentration, to red being zero concentration.

Geometry of hexagons (1) Geometry of hexagons (2)

Project partners

This project is funded by the EPSRC Life Sciences Interface (GR/S04871/01) and is work with Professor Annette Bunge at the Colorado School of Mines and Professor Martin Berzins at the SCI Institute, University of Utah, on leave from Leeds.

Introduction - Transient - Periodicity - Hexes - Anisotropy - Patches

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