Visual observation of selective elution of components from skin-mimetic lipid membrane.

Selective elution of components was visually observed on a mixture of lipids (ceramide III, palmitic acid, and cholesterol) as a mimicry of stratum corneum (SC) which was melted and sandwiched between glass plates. The lipid membrane was exposed to an aqueous solution of sodium dodecyl sulphate (SDS) and observed by an optical microscope. The contact of the lipid membrane with a SDS solution caused the elution of the lipid component as "myelin-form", and the lipid membrane changed to a sponge structure. An infrared absorption spectroscopic study revealed that the SDS penetrated into the lipid mixture, and the fraction of ceramide in the sponge phase became higher than that in the lipid membrane before SDS treatment. The selective elution behaviour was confirmed by observing the behaviour of each component in lipid membrane by means of a fluorescence-staining method: The cholesterol was eluted with producing visual myelin-form on the contact with a SDS solution, and the following elution of palmitic acid occurred without myelin-form, while the ceramide III resisted the exposure to the SDS solution. These results are valid to elucidate the influence of surfactants on SC.