FOURIER-TRANSFORM RAMAN-SPECTROSCOPY OF INTERACTIONS BETWEEN THE PENETRATION ENHANCER DIMETHYL-SULFOXIDE AND HUMAN STRATUM-CORNEUM

The stratum corneum, the outermost layer of human skin, is the major barrier to transdermal delivery of most drugs. Dimethyl sulfoxide (DMSO) is an established penetration enhancer. To assess its mechanism of flux enhancement, Fourier transform (FT) Raman spectroscopy was used to study the effects of a series of aqueous solutions of DMSO on hydrated human stratum corneum following treatment for 1 h. The results showed changes in the stratum corneum keratin from an alpha-helical to a beta-sheet conformation. In addition, at concentrations greater than or equal to 60% v/v, at which DMSO enhances drug flux, there was evidence of interactions with stratum corneum lipids. These observations suggest that the skin penetration enhancement produced by DMSO not only involves changes in protein structure but may also be related to alterations in stratum corneum lipid organization, besides any increased drug partitioning effects.