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Mechanisms of Tape Stripping and Protein Quantification
By: Ali Alikhan, MD, and Howard I. Maibach, MD
Posted: February 26, 2010, from the March 2010 issue of Cosmetics & Toiletries.
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Varying Adhesive Tapes
Tape construction influences the outcome.11 Three different adhesive tapes—one based on rayon, another on polyethylene, and a third proprietary adhesive tape—utilized in vivo showed statistically equivalent mean water diffusion coefficients, SC permeability and SC mass/thickness removal;3 however, after 40 strips, the proprietary adhesive stripped the most while the rayon adhesive stripped the least.3 TEWL increased significantly as deeper SC layers were reached with the proprietary and polyethylene adhesives but not with rayon tape.3
Tape properties, subject properties or a combination thereof may account for the variations in barrier disruptive properties. Variations may also be accounted for by unique adhesive systems; adhesives of different tape brands may bind similarly to cellular SC but differently to extracellular components of the SC barrier. These extracellular components such as free fatty acids, ceramides and lipids are essential to barrier function.
Furthermore, 5-7 µm of SC removal resulted in significant TEWL elevations, a depth unobtainable by the rayon tape (see Table 2).3 This implies that structural elements of the water barrier may not be homogeneously distributed. In some subjects, neither the proprietary adhesive nor the polyethylene adhesive disrupted the water barrier. These individuals experienced no barrier disruption at any of the six tested sites, suggesting the variation of water barrier disruption to be a function of the individual.
Demonstrating that removal of the same amount of SC from different individuals does not result in similar increases in TEWL, Kalia et al. asked whether this variation was secondary to differences in intact membrane thickness between individuals.14 These researchers demonstrated that once differences in the thickness of the intact SC between individuals are normalized, the same degree of barrier disruption induces the same increase in TEWL in each individual.14
Normalizing the SC thickness involves removing SC with respect to the calculated total SC thickness. Therefore, removal of the same percentage of SC in two individuals results in equivalent barrier disruption. TEWL rises considerably only after about 75% of the SC has been removed, presenting a consistent barrier to water loss in the healthy human population.14