Stratum comeum tape stripping

Bashir SJ, Chew AL, Anigbogu A, Dreher F, Maibach HI. Physical and physiological effects of stratum comeum tape stripping. Skin Res Technol. 2001 7 40-8. 

The pH of intact skin ranges from about 4.8 to 6.0, while interstitial fluid exhibits a pH that is near neutral. The low pH on skin is attributed mainly to the presence of the so-called acid mantle , a natural skin barrier to the external environment [172], Wagner et al. [173] measured both in-vivo and in-vitro pH profiles across human stratum comeum (SC) using the tape stripping technique and a flat surface pH electrode (InLab 426 from Mettler Toledo). They found a steep pH increase from pH 6 to 8 in the first 100 pm after the removal of the SC. 

Urocanic acid (2-propanoic acid 3-[lH-imidazol-4-yl] is located superficially in the stratum comeum. Metabolism of epidermal UCA does not occur in situ due to the absence of urocanase, resulting in the accumulation of UCA in the epidermis. Upon UV exposure, naturally occurring trans-UCA converts to the d.s-isomer, in a dose dependent manner, until the photostationary state is reached, when equal quantities of trans- and m-UCA are found in the skin.15 Based on an analysis of the action spectrum for UV-induced immune suppression, and the fact that no immune suppression was observed in mice whose stratum comeum was previously removed by tape stripping, De Fabo and Noonan suggested that urocanic acid was the photoreceptor for UV-induced immune suppression.16 Since the initial experiments many others have documented, the ability of ris-UCA to initiate immune suppression, documented its presence in the serum of UV-irradiated mice, and demonstrated that m-UCA plays a role in UV-induced skin cancer induction. (For a more complete review of the role of m-UCA in immune suppression see two excellent reviews by Norval and colleagues.1718)... 

Skin tape stripping can be used to determine the concentration of chemical in the stratum comeum at the end of a short application period (30 min) and by linear extrapolation predict the percutaneous absorption of that chemical for longer application periods. The chemical is applied to skin of animals or humans, and after a 30-minute skin contact application time, the stratum comeum is blotted and then removed by successive tape applications. The tape strippings are assayed for chemical content. There is a linear relationship between this stratum comeum reservoir content and percutaneous absorption. The major advantages of this method are (1) the elimination of urinary and fecal excretion to determine absorption and (2) the applicability to nonradiolabeled determination of percutaneous absorption, because the skin strippings contain adequate chemical concentrations for nonlabeled assay methodology. 

A dermal absorption rate of 329 mnol/minute/cm ( 60 nmol/minute/cm ) was calculated for the shaved abdominal skin of mice (Tsumta 1975). This is equivalent to a human absorption rate of 29.7 mg/minute, assuming that a pair of hands are immersed in liquid chloroform (Tsumta 1975). However, this calculation was based on the assumptions that the rate of chloroform penetration is uniform for all kinds of skin and that the total surface area of a pair of human hands is 800 cm the former assumption is especially dubious. Islam et al. (1995) investigated the fate of topically applied chloroform in male hairless rats. For exposures under 4 minutes, chloroform-laden water was applied to shaved back skin for exposures of 4-30 minutes, rats were submerged in baths containing chloroform-laden water. Selected skin areas were tape-stripped a various number of times after various delay periods. It appeared that there was an incremental build-up of chloroform in the skin over the first four minutes. When compared to uptake measured by bath concentration differences, approximately 88% of lost chloroform was not accounted for in the stratum comeum and was assumed to be systemically absorbed. 

The intercellular pathway is now accepted as the major pathway for absorption. Recall that the rate of penetration is often correlated with the partition coefficient. In fact this is a very tortuous pathway, and the h (skin thickness) in Fick s first law of diffusion is really 10 x the measured distance. By placing a solvent (e.g., ether, acetone) on the surface or tape stripping the surface, the stratum comeum (SC) is removed, and absorption can be significantly increased by removing this outer barrier. This may not be the case for very lipophilic chemical. This is because the viable epidermis and dermis are regarded as aqueous layers compared to the SC. Note that the more lipophilic the drug, the more likely it will form a depot in the SC and be slowly absorbed over time and thus have a prolonged half-life. 

Martin, E., Neelissen-Subnel, M.T.A., De Haan, F.H.N., and Bodde, H.E. A critical comparison of methods to quantify stratum comeum removed by tape stripping. Skin Pharmacol. 9, 69-77 (1996). 

Whole-animal studies assess the percent of the applied dose absorbed into the body using classic techniques of bioavailability, where absorbed chemical is measured in the blood, urine, feces, and tissues with mass balance techniques. Recently, methods have been developed to assess absorption by measuring the amount of chemical in the stratum comeum because it is the driving force for diffusion. Cellophane tape strips are collected 30 minutes after chemical exposure and the amount of drug assayed in these tape strips correlates to the amount systemically absorbed. If the focus of the research is to determine the amount of chemical that has penetrated into skin, core biopsies may be collected and serially sectioned, and a profile of the chemical as a function of skin depth may be obtained. 

The inclusion of ethanol in commercially available transdermal systems has naturally provoked curiosity concerning its role as an enhancer in human skin, particularly in vivo. The mechanism by which ethanol compromises the human stratum comeum in vivo was investigated by Bommannan et al. [125] using ATR-IR in studies analogous to those described previously in this chapter [61 ]. Those in vivo studies on the untreated ventral forearm of healthy adults had revealed a depth-dependent ordering and reduction of the intercellular lipids relative to the superficial layers. Consequently, in the ethanol experiments, the measurement site (about 20 cm ) was tape stripped four times prior to ethanol treatment in order to isolate the effect of ethanol from the inherent lipid changes in untreated SC. The examination site was treated for 30 minutes with absolute ethanol (10 ml) and then spectrally examined periodically over the... 

By observing that the skin s electrical resistance substantially decreased as layers were sequentially removed by tape stripping, Yamamoto and Yamamoto [5] demonstrated that the stratum comeum layer is the primary contributor to the skin s electrical resistance. However, Resell et al. [6] have shown that even the slightest abrasion to the skin markedly decreases the skin s resistance. In addition, in Leveque and De Rigal s review [7], it is mentioned that stripping can produce a cracked skin surface, resulting in a defective contact between... 

Chemical contaminants may bind to and react with keratin proteins in the stratum comeum of the skin in occupational exposures under field conditions. The tapestripping method was successfully applied for the removal and quantification of keratin from the stratum comeum for normahzation of extracted amoimts of naphthalene (marker hydrocarbon of jet fuel) from human volimteers experimentally exposed to JP-8 jet fuel (Chao and Nylander-French, 2004). Another study indicated that the naphthalene has a short retention time in the human stratum comeum, and that the tape-stripping method, if used within 20 min of the initial exposure, can be used to determine the amoimt of naphthalene initially in the stratum comeum following a single jet fuel exposure (Mattorano et al., 2004). These studies emphasized... 

Lademann J et al (2006) Penetration studies of topically applied substances optical determination of the amount of stratum comeum removed by tape stripping. J Biomed Opt 11(5) 054026... 

In the in vivo human skin model, a hand is generally placed in the solution under study or a predetermined skin area from the back or forearm is treated for a specified time, after which the material of interest remaining on the skin is removed. Absorption is measured by assessing changes in plasma or urine concentration over time or from stratum comeum concentrations in tape stripping samples [82, 92]. Other methods of detection have been employed and will be discnssed. 

Atopic dermatitis Metronidazole 171 0 Insignificant Cone, in stratum comeum sampled by tape stripping Ortiz et al. [101]... 

Mechanical damage provides one model for a diseased skin state [112, 119, 120]. Mechanical damage and stratum comeum removal by tape stripping can iuCTease transepidermal water loss (TEWL) to a level likely attained in various dermatoses and is the most conunonly utilized method of barrier perturbation due to its simplicity. Abrasion by means of a brash bristle or a needle drawn across the skin s surface has been shown, by transmission electron microscopy, to loosen the top layers of the skin [117]. Abrasion may also enhance and control the delivery of vitamin C, 5-aminolevulinic add, vaccines, and biopharmaceuticals [121-124]. However, mechanical damage has infrequently been anployed either in vitro or in vivo human skin as a means to study absorption enhaneement. 

Dreher F, Modjtahedi BS, Modjtahedi SP, Maibach HI. Quantification of stratum comeum removal by adhesive tape stripping by total protein assay in 96-well microplates. Skin Res Technol. 2005 11 97-101. 

Recently, the distribution of topically applied S-labeled sodium lauryl sulfate in excised human skin was measured by Fullerton et al. [110]. Not surprisingly, most of the radiolabeled surfactant remained at the surface of the skin surface. However, approximately 16% of the surfactant was recovered in the stratum comeum by tape-stripping, 32% was localized in the epidermis, and 8% of the applied dose penetrated into the dermis by 24 h. Interestingly, penetration of sodium lauryl sulfate continues even after the surfactant was removed from the skin surface. 

Considerable progress has been made in the investigation of skin surface alterations by the development and use of skin-surface-stripping systems. The superficial layers of the stratum comeum can be collected easily and without any damage for the subjects by firmly pressing a sticky tape (e.g., D-squame disks) on the skin. When removing the sticky tape (after a few seconds), a few layers of comeocytes are collected and can be analyzed for faint alterations [79]. 

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