Skin-stripping method

A simple, quahtative method is the skin stripping technique (322) which strips off a sampling from the skin with ceUophane tape. Methods have been developed (330,331) in which organisms on the hands ate transferred to gloves and sampled. These methods assess both immediate and persistent effects of antiseptics. In aH tests with antiseptics, suitable neutralizing chemicals for the antiseptics employed are necessary so that surviving bacteria may be recovered and counted. Some of these are lecithin, Lubrol W, Polysorbate, and sodium thiosulfate (322). 

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. 

Skin Segmentation Studies — Tape Stripping Method... 

Taken together, sufficient background information exists to begin to permit to the use of stripping method to define the role of individual agents and combinations thereof on so called dry skin syndrome. 

The tape-stripping method initially described by Rockl et al. [19,20] appears to be a valuable and versatile tool for providing information on the distribution of bacteria in and on the skin [19-21], The tape method has been used as a reliable inexpensive diagnostic tool for quantitative determination of, for example, Pityro-sporum yeast [22], Candida spp. [23], Enterobius spp. [24], and Trichophyton spp. [25], The tape method was found to be more sensitive than swab testing, skin scraping, and direct impression techniques for the determination of quantitative and distribution data of Malassezia spp. on canine skin [26],... 

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... 

Zhai et al. [176] utilized an in vitro model to compare the decontamination efficacy of tap water, isotonic saline, and hypertonic saline mixed with " C-radiolabeled glyphosate [176], After exposure, the skin samples were washed three times with 4 mL of each solution. The tape stripping method was used to collect SC samples, and these were analyzed by liquid scintillation counting to determine the radioactivity. Their results showed that there were no statistically significant differences between the various decontamination solutions tested for glyphosate. The total mass removed and the wash-off rates at three different exposure durations ranged from 94.8 to 102.4 % and 79 to 101.2 %, respectively. Therefore, all tested decontamination solutions were similarly effective [176]. 

The traditional methods for evaluation of the delivery and metabolism of exogenous materials in skin involve the use of diffusion cells and/or tape stripping followed by HPLC and mass spectrometry. These methods involve modification of the skin, provide no spatial information, and may alter skin transport properties. In this section, both the permeation and metabolism of a-TAc are monitored inside skin with confocal Raman microscopy. 

Methods used to measure skin pH are, from the analytical point of view, of the same type as those for determining the pH values in aqueous solutions. The earliest studies about skin pH were conducted with colorimetric methods, using indicators that change color with pH. This method is complicated, involving collection of indicator solution from the skin. It was simplified by usage of indicator-impregnated strips (foil-colorimetry).2 5-6... 

Potentiometric methods are easier to use and are nowadays the most frequently utilized to measure outside skin pH. They are also used to establish pH in deeper layers of the epidermis, by first exposing them, for example, by tape stripping.7 The most common potentiometric method is using the hydrogen ion-selective glass electrode with internal reference electrode, which is often called just glass electrode. 6 8 The electrode is often planar-shaped to make it more easily applied on the skin.9... 

The outermost skin layer, the stratum corneum (SC), consists of corneocytes embedded in lipid layers and represents the main barrier for skin penetration of xenobiotics. Its thickness in healthy adults may vary from 5 to 20 /um, except in the palm and sole where it is much thicker. SC can be removed sequentially by repeated application of appropriate adhesive tapes.1 This technique, commonly known as SC tape stripping, is a relatively noninvasive method to investigate the structure, properties, and functions of SC in vivo2 and is the most frequently used for such purposes. Other techniques to remove SC are skin surface biopsy using cyanoacrylate strips and skin scraping. 

Tape stripping can be further used to investigate intercorneocyte cohesion within the SC by quantifying the amount of SC removed.11 When using standardized tape stripping conditions, the more SC removed, the smaller the SC cohesion. For instance, tape stripping in combination with a protein assay to accurately quantify SC removal proved to be a sensitive method in detecting keratolytic efficacy of salicylic acid preparations within hours of application.27 This method may also be useful to measure the influence of moisturizers or other skin care preparations on SC cohesion. 

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

Slush casting, also called slush molding or cast molding, is extensively used. It is a method where TPs in a liquid form are poured into a hot mold that is stationary or moving where a viscous skin forms. The excess slush is drained off, the mold is cooled, and the molding stripped out. Used to produce rain or snow boats, auto instrument panels, over shoes, corrugated and non-corrugated complex tubes, caps, etc. 

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. 

This chapter provides an overview of factors affecting dermal absorption. Factors influencing absorption are among others related to the skin (e.g. anatomical site, difference between species, metabolism, etc.) and the exposure conditions (e.g. area dose, vehicle, occlusion and exposure duration). In order to provide relevant information for the risk assessment of pesticides, dermal absorption studies should take these aspects into account. With respect to the methods being used nowadays for the assessment of dermal absorption, it is important to realize that neither in vitro nor in vivo animal studies have been formally validated. Available data from various in vitro studies, however, indicate that the use of the total absorbed dose (i.e. the amount of test substance in the receptor medium plus amount in the skin) could be used in a quantitative manner in risk assessment. Tape stripping of the skin can be adequate to give a good indication of test chemical distribution, and hence its immediate bioavailability. 

There are few published data on the percutaneous absorption of sunscreens through human skin (239,242-248). Most of the information came from in vitro penetration studies or by estimation from the amount recovered in the stratum corneum after tape stripping. The rationale for using the latter method (often referred to as the "reservoir technique") is based on the finding by Treffel and Gabard (248)that a linear relationship exists between the drug concentration in the stratum corneum and its in vivo percutaneous absorption. 

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