A CRITICAL COMPARISON OF METHODS TO QUANTIFY STRATUM-CORNEUM REMOVED BY TAPE STRIPPING

Skin surface stripping with adhesive tape has been used to study the b arrier function of the stratum corneum. Usually, the amount of stratum corneum removed by stripping is not linearly proportional to the numb er of strips removed. The generally accepted quantitative method to de termine the amount of stratum corneum material on a tape strip is weig hing. This method however has certain drawbacks, it is time consuming and laborious because tape strips have to be weighed twice and sometim es it cannot be used to determine concentration profiles in the skin o f active substances in topically applied vehicles. In this paper, the accuracy and reliability of an alternative method to determine the amo unt of stratum corneum removed by tape stripping of the skin was inves tigated and compared to weighing. It is based on the spectrophotometri c examination of the tape. The light absorption by the proteins on the tape is correlated to the weight of the stratum corneum material. Thi s method was found to be easier and faster than weighing, but it was l ess reliable because the light scattering of the stratum corneum on th e tape largely overshadowed the absorption of the proteins. The light scattering showed a linear increase with an increasing amount of mater ial on the tape, but with a large variability, resulting in calibratio n curves with correlations of 0.8400. However, direct spectroscopic an alysis of stratum corneum tape strips has some distinct advantages eve n if it cannot be used for the exact quantification of stratum corneum proteins. With direct spectroscopic measurements, a tape strip can be laterally examined to inspect its homogeneity. Direct spectroscopic m easurements on tape strips might also be employed to investigate the l ateral and in-depth distribution of strongly light-absorbing substance s in the stratum corneum.