Tape Stripping Technique Research Articles

Mathematical description of the uptake of hydrocarbons in jet fuel into the stratum corneum of human volunteers

The objective of this research was to develop a mathematical description of uptake of aromatic and aliphatic hydrocarbons into the stratum corneum of human skin in vivo. A simple description based on Fick's laws of diffusion was used to predict the spatiotemporal variation of naphthalene, 1- and 2-methylnaphthalene, undecane, and dodecane in the stratum corneum of human volunteers. The estimated values of the diffusion coefficients for each chemical were comparable to values predicted using in vitro skin systems and biomonitoring studies. These results demonstrate the value of measuring dermal exposure using the tape-strip technique and the importance of quantifying of dermal uptake.

Lipid nanoparticles for prolonged topical delivery: An in vitro and in vivo investigation

Dermal therapy is still a challenge due to the difficulties in controlling the active pharmaceutical ingredient (API) fate within the skin. Recently, lipid nanoparticles have shown a great potential as vehicle for topical administration of active substances, principally owing to the possible targeting effect and controlled release in different skin strata. Ketoprofen and naproxen loaded lipid nanoparticles were prepared, using hot high pressure homogenization and ultrasonication techniques, and characterized by means of photo correlation spectroscopy and differential scanning calorimetry. Nanoparticle behavior on human skin was assessed, in vitro, to determine drug percutaneous absorption (Franz cell method) and, in vivo, to establish the active localization (tape-stripping technique) and the controlled release abilities (UVB-induced erythema model). Results demonstrated that the particles were able to reduce drug penetration increasing, simultaneously, the permeation and the accumulation in the horny layer. A prolonged anti-inflammatory effect was observed in the case of drug loaded nanoparticles with respect to the drug solution. Direct as well as indirect evidences corroborate the early reports on the usefulness of lipid nanoparticles as carriers for topical administration, stimulating new and deeper investigations in the field.

Solid lipid nanoparticles (SLN) as carriers for the topical delivery of econazole nitrate: in-vitro characterization, ex-vivo and in-vivo studies

Solid lipid nanoparticles (SLN) designed for topical administration of econazole nitrate (ECN), were prepared by o/w high-shear homogenization method using different ratios of lipid and drug (5:1 and 10:1). SLN were characterized in terms of particle size, morphology, encapsulation efficiency and crystalline structure. After incorporation of SLN into hydrogels, rheological measurements were performed, and ex-vivo drug permeation tests were carried out using porcine stratum corneum (SC). In-vivo study of percutaneous absorption of ECN as a function of application time and composition of gels was carried out by tape-stripping technique. Penetration tests of the drug from a conventional gel were performed as comparison. High-shear homogenization method resulted in a good technique for preparation of ECN-loaded SLN. Particles had a mean diameter of about 150 nm and a regular shape and smooth surface. The encapsulation efficiency values were about 100%. Ex-vivo tests showed that SLN were able to control the drug release through the SC; the release rate depended upon the lipid content on the nanoparticles. In-vivo studies demonstrated that SLN promoted a rapid penetration of ECN through the SC after 1 h and improved the diffusion of the drug in the deeper skin layers after 3 h of application compared with the reference gel.

Development, Evaluation and Data Acquired with a Tape-Stripping Technique for Measuring Dermal Exposure to Budesonide at a Pharmaceutical Manufacturing Site

Although corticosteroids have been used for over 50 years as anti-inflammatory and anti-proliferative agents, few studies have examined their exposure levels and health effects on workers employed in the corticosteroid manufacturing industry. The aims of the study reported here were to develop a tape-stripping technique for monitoring budesonide (a corticosteroid used in inhalators for treating respiratory diseases) and to apply the method in a pilot study to estimate the potential dermal exposure to budesonide among workers at a pharmaceutical formulation site. The tape-stripping method was evaluated by applying 0.5 and 2.07 microg of budesonide dissolved in ethanol on tape strips. The same amounts were also applied on a cleaned glass plate and human skin of volunteers, which were then stripped by series of tapes immediately, and 30 min later, the amounts collected by the tapes were measured. Finally, the technique was used to study the exposure of budesonide among eight employees at a pharmaceutical industry site. Three exposure sites were tested: the tip of the forefinger, palm of the hand and ventral part of the lower arm. Five consecutive tape strips per sampling site were used in both the recovery studies and the field study. The mean overall recoveries from spiked tapes and the glass plate were 96 and 81%, respectively, while for human skin the corresponding figure was 38%, (for applications of 2.07 microg; no detectable amounts were recovered from human skin after 0.5 microg applications). The recovered amount was found on two consecutive tapes after 0 min, but only on the first tape strip after 30 min. The inter-individual variability was 4-fold. In the field, quantifiable amounts were found for four of eight employees and a concentration gradient was detected along the two or three consecutive tape strips. The tip of the forefinger and the palm of the hand were the most highly exposed sites to budesonide. A tape-stripping method can be used to determine potential dermal exposure to budesonide. The results also indicate that budesonide is taken up by the skin of operators who are exposed to the substance at their workplace.

Generation and distribution of reactive oxygen species in the skin of hairless mice under UVA: studies on in vivo chemiluminescent detection and tape stripping methods

Although the formation of reactive oxygen species (ROS) in the skin induced by the ultraviolet (UV) light has been shown to lead to many cutaneous disorders, skin cancer and photoageing, the mechanism and distribution of ROS generation has not yet been definitively determined. In the present study, we examined the distribution of UVA-induced ROS in the skin of live hairless mice, using our proposed in vivo imaging chemiluminescent (CL) method to detect ROS combined with a CL probe (cypridina hilgendorfii luciferin analogue; CLA) and tape stripping (TS) technique. The CL intensities in the skin of live hairless mice were confirmed to significantly increase by UVA exposure. When TS was conducted five times in a maximum level after CL measurement following UVA exposure and subsequent CLA application, CL intensities due to UVA-induced ROS generation in the residual skin decreased to 10% of the original levels; and those in the stripped skin on each tape decreased in the stripped order such as 52%, 16%, 11%, 6% and 5%. Next, CLA was applied and then CL intensities were measured in the residual skin after advance 1, 3 and 5 tape strippings, and CL intensities due to ROS were detected primarily in the outer layer of the skin. On the basis of these results, we concluded that ROS induced by UVA exposure occurs and distributes in the outermost layer of the stratum corneum.

Design and Evaluation of a Self-Adhesive Naproxen-Loaded Film Prepared from a Nanoparticle Dispersion

Naproxen-loaded nanoparticles were used to prepare, in a one-step process, unilaminar films of Eudragit E-100 (EE-100), avoiding the use of organic solvents and assuring the homogeneity and molecular dispersion of the drug. Nanoparticle films (NP-F) and conventional films (CV-F, prepared by casting of methanolic solutions onto a Teflon disc) were assayed by their mechanical properties, skin adhesivity, and calorimetric studies to compare their behavior. Different proportions of plasticizer (triacetin) were included to evaluate the quality of the films. Film characterization included in vitro drug release studies through a cellulose membrane using Franz-type cells, and in vivo stratum corneum penetration experiments by the tape stripping technique. The results showed that NP-F were semi-transparent to transparent, suggesting a good compatibility between naproxen and EE-100. Differential calorimetric studies (DSC) confirmed a molecular dispersion of naproxen in the EE-100 matrix. Taking into account the mechanical properties of the films, a 20% triacetin concentration can be considered as optimal for both types of films. The in vitro release data obtained from both systems (NP-F and CV-F) followed the Higuchi's model for matrix systems, with the Fickian diffusion (t(0.5)) being the main release mechanism. Concerning the in vivo penetration studies, no statistical differences were found for the penetrated amount of naproxen across the stratum corneum and the depth of penetration for the two films and between the three contact times (2, 4, and 6 h). The films formulated from nanoparticle dispersions (NP-F) were shown to be effective for the transdermal administration of naproxen, and can be considered as an interesting alternative for the preparation of films with several technological advantages.

Percutaneous penetration of sodium lauryl sulphate is increased in uninvolved skin of patients with atopic dermatitis compared with control subjects

Involved regions of the skin in patients with atopic dermatitis (AD) have been shown to have higher transepidermal water loss (TEWL), indicating a compromised skin barrier. Whether uninvolved skin also has diminished barrier characteristics is controversial. To study the penetration of sodium lauryl sulphate (SLS) into uninvolved skin of patients with AD compared with the skin of control subjects. Percutaneous penetration was assessed using the tape stripping technique on the stratum corneum (SC). Twenty patients with AD and 20 healthy subjects were exposed to 1% SLS for 4 h on the mid-volar forearm. After the end of exposure the SC was removed by adhesive tape. The amount of SLS was determined in each consecutive strip. Fick's second law of diffusion was used to deduce the diffusivity and the partition coefficient of SLS between water and the SC. The SC thickness was similar in both groups; however, the TEWL was higher in patients with AD compared with that of the control group (mean+/-SD 8.4+/-4.3 and 6.3+/-2.0 g m-2 h-1, respectively). There was a correlation between SC thickness and TEWL in control subjects but no correlation was found in patients with AD. The diffusivity of SLS through uninvolved AD skin was higher compared with normal skin (mean+/-SD 12.7+/-5.8x10(-9) and 6.2+/-3.0x10(-9) cm-2 h-1, respectively), while the partition coefficient between SC and water was lower (mean+/-SD 137+/-64 and 196+/-107, respectively). The results show a different penetration profile of SLS into the SC of patients with AD compared with control subjects. This indicates that even noninvolved skin in patients with AD has altered barrier characteristics, emphasizing the importance of skin protection and prevention of skin contact with chemicals.

Advantages of NIR radiation use for optical determination of skin horny layer thickness with embedded TiO2 nanoparticles during tape stripping procedure

The tape stripping technique is an experimental method frequently used for reconstruction of the in-depth distribution of various topically administered substances within the horny layer of human skin, e.g., compounds contained in sunscreens. Titanium dioxide (TiO2) nanoparticles (25–200 nm in diameter) are one such compound. Optical techniques which apply blue light are found to be suitable for reconstruction. However, the presence of particles affects the light propagation within the skin and therefore causes incorrect determination of strip thickness, leading to an improper reconstructed distribution of nanoparticle concentration revealed from the experimental data. This study evaluates the errors emerging from the use of blue (400 nm) and NIR (800 nm) radiation and finds the use of longer wavelength light more advantageous. Particles of different diameters are considered, and it is revealed that the application of small particles (25–60 nm) results in the lowest rate of error.

Measuring Dust on Skin with a Small Vacuuming Sampler—A Comparison with Other Sampling Techniques

Airborne skin exposure to allergens and irritants may cause dermatitis. There are few methods for assessing skin exposure to airborne particles. We have modified and tested a vacuuming sampler for removing particles from the skin. The sampler was compared with two other skin and surface exposure sampling techniques. These were based on surrogate skin (a patch sampler-adhesive tape on an optical cover glass) and a tape stripping removal procedure. All three samplers measure the mass of dust on skin. Dust containing starch was deposited onto the skin in a whole-body exposure chamber. Samples were taken from forearms and shoulders and analysed using optical microscopy. With the different sampling techniques small differences in the results were obtained. Agreement between the vacuuming sampler and the tape stripping technique was good. The comparison between patch and tape stripping procedure indicated a slight overestimation for the patch. The three techniques are applicable for assessing skin exposure to particles and for dose-effect studies. The vacuuming method will be further developed and applied in workplace studies. The technique allows for dust sampling from large areas of skin.

TiO2 nanoparticles as an effective UV-B radiation skin-protective compound in sunscreens

Protecting human skin against harmful UV-B radiation coming from the sun is currently a problem. Due to the decreased thickness of the ozone layer, a more dangerous amount of UV-B light reaches the surface of our planet. This causes increased frequency of skin diseases. Titanium dioxide (TiO2) fine particles are embedded with sunscreens into the skin to effectively attenuate UV-B radiation. This study evaluates the most appropriate size of such particles assuming they are spheres. The distribution of TiO2 particles within the skin, achieved with topically applied sunscreens, is determined experimentally by the tape-stripping technique. Computer code implementing the Monte Carlo method is used to simulate photon migration within the plain 20 µm thick horny layer matrix partially filled with nano-sized TiO2 particles. Dependences of harmful UV-B radiation of 307–311 nm absorbed by, backscattered from and transmitted through the horny layer on the concentration of TiO2 particles are obtained and analysed. As a result, particles of 62 nm are found to be the most effective in protecting skin against UV-B light.

Dermal Exposure to Jet Fuel (JP-8) in US Air Force Personnel

Limited research has been conducted on dermal exposure and risk assessment, owing to the lack of reliable measurement techniques and data for quantitative risk assessment. We investigated the magnitude of dermal exposure to jet propulsion fuel 8 (JP-8), using naphthalene as a surrogate, on the US Air Force fuel-cell maintenance workers. Dermal exposure of 124 workers routinely working with JP-8 was measured using a non-invasive tape-strip technique coupled with gas chromatography-mass spectrometry analysis. The contribution of job-related factors to dermal exposure was determined using multiple linear regression analyses. Average whole body dermal exposure to naphthalene (as a marker for JP-8) was 7.61 +/- 2.27 ln(ng m(-2)). Significant difference (P < 0.0001) between the high-exposure group [8.34 +/- 2.23 ln(ng m(-2))] and medium- and low-exposure groups [6.18 +/- 1.35 ln(ng m(-2)) and 5.84 +/- 1.34 ln(ng m(-2)), respectively] was observed reflecting the actual exposure scenarios. Skin irritation, use of booties, working inside the fuel tank and the duration of JP-8 exposure were significant factors explaining the whole body dermal exposure. This study clearly demonstrates the efficiency and suitability of the tape-strip technique for the assessment of dermal exposure to JP-8 and that naphthalene can serve as a useful marker of exposure and uptake of JP-8 and its components. It also showed that the skin provides a significant route for JP-8 exposure and that actions to reduce exposure are required. Studies to investigate the relative contribution of dermal uptake of JP-8 on total body dose and the toxicokinetics of dermal exposure to JP-8 are underway.

Preparation of polymeric nanocapsules containing octyl methoxycinnamate by the emulsification–diffusion technique: Penetration across the stratum corneum

Polymeric nanocapsules (NCs) containing octyl methoxycinnamate (OMC) as lipophilic molecule were prepared, and their in vivo distribution profile through the stratum corneum (SC) was determined by the tape-stripping technique. Penetration degree of OMC formulated in NCs was compared with that obtained for a nanoemulsion (NE), and a conventional oil-in-water (o/w) emulsion (EM). To produce stable cellulose acetate phthalate (CAP) nanocapsules containing the lipophilic sunscreen, a study was conducted to optimize the process of NC preparation based on the emulsification–diffusion technique. NC formation was verified by measuring their density using differential centrifugation. NC density revealed that an OMC (µL)/CAP (mg) ratio of 2.5:1 is optimal for encapsulation. High encapsulation entrapment (>96%) and excellent process efficiency (recovered quantity of NCs in relation with the initial amount of OMC and CAP >99%) were always achieved with this ratio or a higher one. The capsular structure of the NCs was evidenced with a direct SEM technique. NE was prepared by the emulsification–diffusion technique, dissolving a specific quantity of OMC in water-saturated 2-butanone and then, emulsifying with an aqueous solution of PVAL. In vivo percutaneous penetration, evaluated by the tape-stripping technique, demonstrated that NE increased the extent of OMC penetration relative to the penetration achieved by NCs or EM, with relative penetration depths through the SC of 0.86±0.1, 0.64±0.11, and 0.57±0.08, respectively. In the same manner, the accumulation in the skin of OMC was significantly greater with NE than with EM or NCs. OMC penetration depth was strongly dependent upon the size of the colloidal particles and their flexibility. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association.

Evaluation of Indomethacin Percutaneous Absorption from Nanostructured Lipid Carriers (NLC): In Vitro and In Vivo Studies

The aim of this study was the evaluation, in vitro and in vivo, of indomethacin (IND) release through the skin from nanostructured lipid carriers (NLC). NLC were prepared by ultrasonication, and were characterized in order to determine drug content, and particle size; finally the NLC were processed to hydrogels (A and B). The IND release pattern from NLC hydrogels was evaluated in vitro, to determine its percutaneous absorption through excised human skin (stratum corneum and epidermis, SCE), and in vivo. To evaluate the in vivo IND release, two methods were employed: (1) the IND topical anti-inflammatory activity was determined at different timepoints after its cutaneous application; in this case, the UVB-induced erythema on healthy human volunteers, chosen as inflammatory model, was monitored by reflectance visible spectrophotometry; (2) the extent of IND absorption into human skin was performed by the tape-stripping technique. The in vitro percutaneous absorption studies showed lower fluxes of IND through SCE membranes from NLC hydrogels (A and B) in comparison to an aqueous dispersion (C) and a hydro-alcoholic gel (D) both containing free IND. The findings from the former in vivo method showed that the anti-inflammatory effect, following IND topical application, was more prolonged with IND-loaded NLC gel formulation (A) if compared to formulation C and D. The results from tape stripping technique confirmed the trend obtained by the former in vivo method and indicated that IND topical bioavailability in the stratum corneum varied substantially depending upon the formulations (A–D). © 2005 Wiley-Liss, Inc. and the American Pharmacists Association

Reservoir Function of the Stratum corneum: Development of an in vivo Method to Quantitatively Determine the Stratum corneum Reservoir for Topically Applied Substances

Investigations on the stratum corneum (SC) reservoir for topically applied substances are of importance in dermatologic science in order to assess the pharmacokinetics of these substances. In the present study, an in vivo method was developed to determine the SC reservoir quantitatively and to investigate the temporal behavior of this reservoir. Therefore, increasing amounts of an oil-in-water emulsion (o/w emulsion) containing 4% of a chemical UV filter were topically applied onto the flexor forearms of 5 healthy volunteers. The saturation of the SC reservoir was determined utilizing the tape stripping technique 1 and 6 h after application. The capacity of the SC reservoir for the o/w emulsion was found to be approximately 2.7 mg/cm². Furthermore, a correlation of the capacity of the SC with transepidermal water loss was observed. Extending the time between the topical application and SC removal did not affect the distribution or the recovery rate of the UV filter in the SC. The results indicate that the reservoir of the SC is limited. This is reflected by the saturation level, which depends on the individual volunteer and, presumably, the topically applied substances and formulations used. The results show that the method developed is suited to quantitatively determine in vivo the SC reservoir for topically applied substances.

Effect of size of TiO[sub 2] nanoparticles embedded into stratum corneum on ultraviolet-A and ultraviolet-B sun-blocking properties of the skin

Recently there has been a strong demand to protect human skin against negative effects of the UV solar light. This problem is interesting due to the increased frequency of human diseases caused by such radiation. We aim to evaluate how the optical properties of the horny layer of skin can be effectively changed by imbedding TiO2 fine particles to achieve the maximal attenuation of the UV solar radiation. In-depth distribution of TiO2 particles embedded into the skin by multiple administration of sunscreens is determined experimentally using the tape-stripping technique. A computer code implementing the Monte Carlo method is developed to simulate photon migration within the 20-microm-thick horny layer filled with nanosized TiO2 spheres, 25 to 200 nm in diameter. Dependencies of the UV radiation of two wavelengths (310 and 400 nm) absorbed by and totally reflected from, as well as transmitted through the horny layer on the size of TiO2 particles are obtained and analyzed. The most attenuating particles are found to be 62 and 122 nm in diameter for 310- and 400-nm light, respectively. The former could be suggested as the main fraction to be used in sunscreens to prevent erythema.

Unexpected clobetasol propionate profile in human stratum corneum after topical application in vitro.

The validity of using drug amount-depth profiles in stratum corneum to predict uptake of clobetasol propionate into stratum corneum and its transport into deeper skin layers was investigated. In vitro diffusion experiments through human epidermis were carried out using Franz-type glass diffusion cells. A saturated solution of clobetasol propionate in 20% (V/V) aqueous propylene glycol was topically applied for 48 h. Steady state flux was calculated from the cumulative amount of drug permeated vs. time profile. Epidermal partitioning was conducted by applying a saturated drug solution to both sides of the epidermis and allowing time to equilibrate. The tape stripping technique was used to define drug concentration-depth profiles in stratum corneum for both the diffusion and equilibrium experiments. The concentration-depth profile of clobetasol propionate in stratum corneum for the diffusion experiment is biphasic. A logarithmic decline of the drug concentration over the first four to five tape strips flattens to a relatively constant low concentration level in deeper layers. The drug concentration-depth profile for the equilibrium studies displays a similar shape. The shape of the concentration-depth profile of clobetasol propionate is mainly because of the variable partitioning coefficient in different stratum corneum layers.

PH profiles in human skin: influence of two in vitro test systems for drug delivery testing

Investigations to determine pH profiles across human stratum corneum (SC), in vivo as well as in vitro, were carried out using the tape stripping technique and a flat surface pH electrode. This method was extended to the deeper skin layers (=viable epidermis+dermis; DSL) in vitro. Statistically significant changes in the pH values were detected in the SC between in vivo and in vitro investigations and also between male and female skin in vivo. For the DSL, no gender-dependent differences in pH were observed. While the results achieved for the SC are in accordance with data already published in the literature, the values for the DSL were surprising: An alkaline pH, with a steep increase of about two pH units in the first 100 μm of the DSL and a plateau of this level was thereafter detected. Research was also done to examine the influence of different in vitro test systems on the results of pH measurements across the skin. A permeation model (Franz diffusion cell; FD-C) and a penetration model (Saarbruecken penetration model; SB-M) were compared. Experiments were carried out concerning the incubation time as well as the pH of the acceptor solution in the FD-C. Independent of the test system used, no change in the pH profiles could be observed for the SC, but a strong effect of the acceptor medium and its pH on the pH profiles across the DSL could be demonstrated using the FD-C, which showed itself partly after 30 min in statistically significant differences between incubated and formerly frozen skin. The results after the use of buffer solutions with different pH values, the pH across the DSL seemed to come into line with the one of the buffer solution, which was investigated for acidic as well as alkaline pH values. The results obtained with the flat surface pH electrode were confirmed using two different dyes: the pH-dependent fluorescent dye carboxy-SNARF-1 and the pH indicator bromthymolblue.

Comparison of two sampling techniques to assess quantity and distribution ofMalasseziayeasts on the skin of Basset Hounds

Cytological examination using the tape-strip technique and fungal culture using contact plates with modified Dixon's medium were compared to evaluate the carriage of Malassezia yeasts on four cutaneous sites (left pinna, umbilical region, axilla and perianal area) in adult Basset Hounds. Twenty animals were included in the study. High numbers of Malassezia were isolated from at least one area in 100% of the animals. The frequencies of isolation and population sizes differed significantly according to anatomical location. They were greater on the pinna, followed by the umbilical area, axilla and perianal area. Fungal culture was more sensitive than cytology for the isolation of Malassezia yeasts. Frequencies of isolation were greater using this method, but population sizes were constantly smaller than with cytology.

A tape-stripping method for measuring dermal exposure to multifunctional acrylates

Current methods for measuring dermal exposure to skin irritants and allergens, such as acrylates, have significant drawbacks for exposure assessment. A noninvasive sampling method has been developed and tested for measuring dermal exposure to a multifunctional acrylate employing a tape stripping of the nonviable epidermis (stratum corneum). Samples were subsequently extracted and a gas chromatographic method was employed for quantitative analysis of tripropylene glycol diacrylate (TPGDA). This method was tested in 10 human volunteers exposed to an a priori determined amount of TPGDA or a UV-radiation curable acrylate coating containing TPGDA (UV-resin) at different sites on hands and arms. On the average, the first tape stripping removed 94% (coefficient of variation 16%) of the theoretical quantity of deposited TPGDA and 89% (coefficient of variation 15%) of the theoretical quantity of deposited TPGDA in UV-resin 30min after exposure. Quantities of TPGDA recovered from two consecutive tape strippings accounted for all of the test agent, demonstrating both the efficiency of the method to measure dermal exposure and the potential to determine the rate of absorption with successive samples over time. In general, the amount removed by the first stripping was greater for TPGDA than for UV-resin while the second stripping removed approximately 6 and 21% of TPGDA and UV-resin, respectively. However, when the amounts removed with the first tape stripping for TPGDA or UV-resin from the five different individual sites were compared, no significant differences were observed (P=0.111 and 0.893, respectively). No significant difference was observed in recovery between TPGDA and UV-resin for the first tape stripping when calculated as a percentage of the theoretical amount (P=0.262). The results indicate that this tape-stripping technique can be used to quantify dermal exposure to multifunctional acrylates.

Development of a Low-Metal Adhesive Tape to Detect and Localize Metals in or on the Stratum corneum at Parts per Million Levels

Tape-stripping is a well-established method for sampling the stratum corneum (SC). We have developed a tape with low-metal content suitable for use with particle-induced X-ray emission (PIXE), an analytical technique based on X-ray spectrometry. PIXE analysis of tape-stripped samples of SC is a reliable and minimally invasive means of identifying and quantifying metals present at parts per million levels. Assay feasibility and reproducibility was demonstrated using human volunteers. This new tape-strip technique has potential applications in exposure and decontamination assessment, diagnosis of metal dermatitis, forensics, and in environmental research.