Influence of skin furrows on tape stripping in characterizing the depth of skin penetration.

The stratum corneum (SC), the outermost layer of the skin and its major barrier for penetration, contains furrows of different depths on its surface. The presence of these furrows might lead to erroneous interpretation of the results in skin permeation studies using tape stripping, in which the material trapped in the furrows removed by the tapes representing different layers of the SC might be interpreted as material penetrating within these layers. The present objective was to investigate the effect of skin furrows on tape stripping results. Non-penetrating fluorescent materials were topically applied to split-thickness human and full-thickness porcine skin samples. Tape stripping was applied, and the tapes were assessed by fluorescence microscopy and quantitative analyses. The microscopy images were assessed visually to determine the presence of the applied material in the furrows. The penetration depth of the material was examined and the fluorescence content and pattern in each tape were analyzed. The results suggested that skin furrows could be important in the first 10 tapes, affecting the quantification of materials in the SC, particularly in permeation studies of materials with low penetration into the SC. Depending on the properties of the materials, skin rinsing could reduce the impact of furrows.