Determination of the Horny Layer Profile by Tape Stripping in Combination with Optical Spectroscopy in the Visible Range as a Prerequisite to Quantify Percutaneous Absorption

Abstract

A new method was developed to determine the horny layer profile of volunteers using tape stripping in combination with UV/visible spectroscopy. The optical absorbance and the weight of corneocyte aggregates were compared as parameters for the determination of the mass of the horny layer particles fixed to the individual tapes. It was shown that the potential disturbances influencing both parameters must be considered critically before calculating the correlation factor, found as R²_mean = 0.93 ± 0.05. It was proven that the absorbance in the visible range is better suited than the weight to quantify the amount of corneocyte aggregates removed by a single strip. The new method allows an exact anatomical localization of the individual tapes and all data obtained within the depth profile of the stratum corneum. This was exemplified by the determination of the penetration of chemical and physical UV filters into the horny layer.

Gender-Related Differences in the Physiology of the Stratum Corneum

“…The tape was handled with forceps during the weighing and removal procedure. The tape strips were weighed with a semi-micro balance (BP 211 D-OCE, Sartorius, Göttingen, Germany) before and after the removal of SC, as described previously [23, 24]. The difference between the two measurements was taken as the mass of the removed SC.…”

Titanium dioxide (respirable fraction) [MAK Value Documentation, 2009]

“…For this purpose, the tapes were stained with osmium tetroxide to make the follicular orifices visible. Thus, particle distribution could be correlated with the position of the follicles (Lademann et al 1999;Weigmann et al 1998). In addition, skin biopsies were taken to determine the penetration depth of the coated titanium dioxide into the epidermis.…”

Label free non-invasive imaging of topically applied actives in reconstructed human epidermis by confocal Raman spectroscopy

“…In vivo methods are in general limited by measuring physical properties of the SC barrier such as impedance, water content or water loss of the skin rather than directly tracking the active compound 19 . By tape stripping, penetration profiles of topically applied actives could be determined, but the active concentration is usually averaged per layer and depth 20,21 . The permeation coefficients of topically applied actives are mostly determined in vitro using diffusion cells.…”

“…immune histology, fluorescence microscopy and two-photon imaging) or only sections can be analysed (e.g. energy dispersive X-ray and IR spectroscopy) 20,[32][33][34][35][36][37] .…”