Skin: the ultimate interface.
ABSTRACT The outer layer of the skin, the stratum corneum is a unique barrier membrane. On average it is only 20 μm thick (about a quarter the thickness of a normal sheet of paper) but it prevents us from losing excessive water and it protects us from our environment. It forms a special interface between our body, the air, water and various solids. In order to understand the barrier properties of the skin we need to determine its structure at various levels ranging from the macroscopic scale to the molecular level. This has been made easier by the advances that there have been over the recent decade. However, the amount of a material that is capable of penetrating this excellent barrier and reaching the underlying systemic circulation is still only of the order of 1 or 2 per cent of the total applied dose. The purpose of this publication is to explore the strategies currently employed to promote skin permeation and to consider the most exciting approaches currently under investigation. The limitations of current methodology to examine the problem are discussed. New opportunities to fill the gaps in our current knowledge are identified and the importance of interdisciplinary research in the field is emphasised.
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ABSTRACT: This paper describes a new in vivo Raman probe that allows investigation of areas of the body that are otherwise difficult to access. It is coupled to a previously described commercially available in vivo Raman spectrometer that samples the skin through an optical flat. In the work presented here, the laser light emerges from a smaller pen-shaped probe. It thus works on the same principles as the original spectrometer, while its relative performance in terms of signal-to-noise ratio of the spectra and obtained spatial resolution is only slightly diminished. It allows the window to be placed against the subject in more curved and recessed areas of subject's body and also for them to be more comfortable while the measurements take place. Results from three areas of the body that have previously been very difficult to study are described, the mouth, axilla, and scalp. Results from the scalp and axilla strata cornea (SC) show significant differences from the "normal" SC of the volar forearm. For instance, the scalp is observed to have lower amounts of natural moisturizing factors (NMF) compared to the volar forearm within the same subjects. Also for both the axilla and scalp the lipids show a change in order as compared to the lipids in the volar forearm and also differences from each other. The potential significance of these observations is discussed. Further, we show how we can probe the mouth, in this case observing the presence of the astringent tea polyphenol epigallocatechin gallate within the oral mucosa.Applied Spectroscopy 07/2012; 66(8):882-91. · 1.66 Impact Factor
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ABSTRACT: Topical delivery to the various regions of the skin and underlying tissues, transdermal drug delivery and dermal exposure to environmental chemicals are important areas of research. Mathematical models of epidermal and dermal transport, involving penetration of a solute through various layers of the skin, metabolism in the skin and its subsequent distribution and clearance into systemic circulation from underlying tissues, play an essential role in this research area and are reviewed in this work.Advanced drug delivery reviews 05/2012; · 11.96 Impact Factor