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In vitro
Tape Stripping Method in Humans: Comparison of Evaporimetric Methods
By: Hongbo Zhai, MD, and Howard I. Maibach, MD, University of California School of Medicine
Posted: January 30, 2009, from the February 2009 issue of Cosmetics & Toiletries.
The stratum corneum (SC) has been well recognized as a principal water barrier of the skin. It is a cellular tissue, a fabric of cornified cells creating a tough, flexible, coherent membrane, acting as a two-way barrier, minimizing water loss, electrolytes and other body constituents, and decreasing the entry of noxious substances from the external environment.1,2 Maintenance of the SC structural integrity is critical to barrier function. Transepidermal water loss (TEWL) documents the integrity of SC water barrier function, and is a sensitive indicator of skin water barrier alteration.3 Healthy SC typically has a water content of 10–20%;2 the TEWL can be dramatically altered if this barrier function is perturbed by physical, chemical, therapeutic or pathological factors.4-7
Tape stripping is a commonly used method for investigating SC physiology as well as bioavailability and bioequivalence of topical drugs. The number of tape strips needed to remove the SC varies with age, gender and possibly ethnicity, as well as the application pressure.6,8 A previous publication compared an open and a closed chamber device in measuring TEWL on healthy volunteers.9 However, comparable data on stripped skin with higher evaporation rates remained unavailable.
The current preliminary study compared the sensitivity and correlation of open chamber device and closed chamber device on a tape stripping human model. The amount of SC removed by tape stripping was also quantified with a protein assay method.
Materials and Methods
Subjects: Ten healthy volunteers (6 male and 4 female; 7 Caucasians and 3 Asians; mean age 38 ± 16 years) who met the selection criteria were enrolled after providing informed consent. Subjects had no skin disorders and were instructed not to apply topical products to the test sites for one week prior to and during the study. This study protocol and informed consent form were reviewed and approved by the Committee on Human Research at University of California, San Francisco.
Materials: Tape stripping was performed by skin sampling discsa; these discs will be referred to as tape strips in the following discussion.