Determination of keratin protein in a tape-stripped skin sample from jet fuel exposed skin

Abstract

Chemical contaminants or their metabolites may bind to and react with keratin proteins in the stratum corneum of the skin. Here, we present a tape-stripping method for the removal and quantification of keratin from the stratum corneum for normalization of extracted concentrations of naphthalene (as a marker for jet fuel exposure) from 12 human volunteers before and after exposure to jet fuel (JP-8). Due to the potential for removal of variable amounts of squamous tissue from each tape-strip sample, keratin was extracted and quantified using a modified Bradford method. Confirmation of the extraction of keratin was verified by western blotting using a monoclonal mouse anti-human cytokeratin antibody. Naphthalene was quantified in the sequential tape strips collected from the skin between 10 and 25 min after a single dose of JP-8 was initially applied. The penetration of jet fuel into the stratum corneum was demonstrated by the fact that the average mass of naphthalene recovered by a tape strip decreased with increased exposure time and subsequent tape strips and that the evaporation of naphthalene was observed to be negligible. There were no significant differences in the amount of keratin or naphthalene removed by tape strips between males and females, between age groups, races or degrees of skin pigmentation. We conclude that (i) the amount of keratin removed with tape strips was not affected by up to a 25 min exposure to JP-8 and (ii) there was a substantial decrease in the amount of keratin removed with consecutive tape strips from the same site, thus, adjusting the amount of naphthalene by the amount of keratin measured in a tape-strip sample should improve the interpretation of the amount of this analyte using this sampling approach. Although we found that normalization of the naphthalene to the amount of keratin in the tape-strip samples did not affect the ability of this method to quantify the dermal exposure to JP-8 under these laboratory conditions, the actual concentration of naphthalene (as a marker for JP-8 exposure) per unit of keratin in a tape-strip sample can be determined using this method and may prove to be required when measuring occupational exposures under field conditions.