Optical investigations to avoid the disturbing influences of furrows and wrinkles quantifying penetration of drugs and cosmetics into the skin by tape stripping

Abstract

Furrows and wrinkles, as typical structures of human skin, represent a reservoir for topically applied substances. This reservoir can influence penetration experiments of topically applied substances into the stratum corneum by tape stripping. Optical methods such as laser-scanning microscopy, optical coherent tomography, and the microscopical investigation of histological sections obtained by biopsies were used to check a special protocol, which avoids these potential disturbances. The use of a transparent adhesive film with high flexibility and the realization of an intense contact to the stretched skin by pressing the tape with a roll, moved laterally on the tape, are the prerequisites to obtain correct data. The application of this experimental technique and the performance of tape stripping allow the determination of the horny layer profile and the local distribution of topically applied substance, undisturbed by the characteristic structure of the natural skin. These results demonstrate that the presented tape stripping procedure is a valuable tool to determine, quantitatively, the penetration and the bioavailability of drugs and cosmetics inside the human stratum corneum, in relation to the horny layer profile