Electron resonance studies on the influence of anionic surfactants on human skin

When skin is exposed to chemicals, raw materials interact with the lipid structure of the stratum corneum. At least two types of disorders can be distinguished--that of alkyl chains inside one lipid bilayer and that of lipid layer arrangement. Electron spin resonance (ESR) spectroscopy of a nitroxide spin label is a valuable method in the study of biological membranes.

These experiments define the effect of anionic surfactants on the lipid bilayer of human stratum corneum.

5-Doxyl stearic acid (5-DSA) was used as the spin label. Sodium lauryl sulfate (SLS) and sodium lauroyl-L-glutamate (SLG) were the anionic surfactants studied. ESR spectrum measurements of surfactant-treated stratum corneum were performed and order parameters calculated.

1% of SLS leads to an obvious change in ESR spectra--from strongly to weakly immobilized spectra. The molecular motion of spin labels (5-DSA) in SLS-treated stratum corneum is different from that of spin labels in the untreated stratum corneum. The ESR spectra suggest that SLS affects the spin label binding to the lipid membrane and causes an increase in the mobility of bilayers. On the other hand, there were minimal changes in ESR spectra of 1% of SLG-treated stratum corneum. An increase in fluidity of skin lipid bilayers suggests a decrease in the skin barrier function.

ESR may provide a facile and robust method to define the subclinical irritancy potential of anionic surfactants and other materials.