Human Stratum Corneum Adsorption of Nickel Salts Investigation of Depth Profiles by Tape Stripping In Vivo

Sequential adhesive tape stripping was implemented to characterthe resulting nickel-complexed protein may then cause contact allergy, as well as irritation (1). ize the penetration of nickel salts in human stratum corneum. Exposure areas of the salts in methanol applied open on arm We sought to de ne the characteristics of diVusion of watersoluble nickel salts over 24h throughout the microenvironment and back skin in low volume were stripped 20 times to the level of the glistening layer at intervals of 30 min to 24h post-dosing, of the human SC. We closely examined nickel localization in the SC in vivo, since earlier investigations had raised a number and the strips analyzed for metal content by inductively coupled plasma–atomic emission spectroscopy. In the case of nickel of questions concerning the behavior of nickel in contact with human skin: pronounced allergenicity in spite of low diVusivity chloride, sulfate, nitrate and acetate, material left on the skin surface, the depth-penetration pro les in the stratum corneum, (2–6), dependence of skin permeability on counter ion (2, 3, 6, 7) and anatomical site (8), appendageal penetration (9–11), and the dosage unaccounted for suggest the following conclusions: (a) Up to 24 h, most of the nickel dose applied remains and the formation of depots in the skin (2, 9, 12–14). These observations prompted the investigation of depth pro les on the skin surface or is adsorbed in the uppermost layers of the stratum corneum. (b) At higher concentrations, incomplete obtainable by the non-invasive method of SC stripping with adhesive tape. A closer scrutiny of the surface adsorption material recovery becomes discernible; within 24 h, nickel salts thus appear to penetrate beyond the stratum corneum to a minor dynamics of nickel as prototype of strongly electrophilic metals and its behavior in contact with human skin, as may occur degree, possibly via the skin shunts. (c) While the concentration gradients of nickel adsorbed vary with counter ion, anatomical particularly in the work environment, could clarify some of the unresolved questions associated with the allergenicity and site, dose and exposure time, for all variables tested the depth pro les converge to non-detectable levels (< 20 ppb) towards the dermatotoxicity of that metal. In the present context, the term ‘‘Stratum Corneum level of the glistening layer. A notable exception is nickel as nitrate, for which levels continue at low but constant levels (1% Adsorption’’ is used to indicate that part of the dose applied which is found in the SC; ‘‘Dermal Absorption’’ denotes the of dose) beyond the third stratum corneum strip, indicative of intercellular diVusion. (d) DiVerences in material recovered balance not recovered by decontamination and SC stripping, thus potentially becoming systemically available. suggest that the stratum corneum on the arm is more penetrable to nickel than stratum corneum on the back. (e) The counter ion in nickel salts plays a major part in their diVusion into the stratum corneum, suggestive of ion pairing. Overall, the data MATERIALS AND METHODS point to all three avenues of skin penetrationby nickel: intracelluVolunteers lar, intercellular, and transappendageal.