Tatsuru Tabohashi

Effect of surfactants on human stratum corneum: electron paramagnetic resonance study.

Electron paramagnetic resonance (EPR) spectra of nitroxide spin probes are useful for studying biological membranes and chemical-membrane interactions. Recently, we established a stripping method to remove stratum corneum (SC) for this purpose. To assess this stripping method with EPR and correlate with standard methods, we quantified the irritant effects of three types of surfactants by measurements of visual score and transepidermal water loss (TEWL), SC hydration and chromametry and studied EPR spectra measurements of surfactant-treated cadaver SC (C-SC) and stripped off SC (S-SC) on patch tested sites. 5-Doxyl stearic acid was the spin label. The order parameter S obtained from the spectra of S-SC correlated with those of C-SC and TEWL values. The results suggest that this method is capable of evaluating the fluidity of SC and correlates with the above bioengineering parameters.

Solution properties of amino acid-type new surfactant

The solution properties of an amino acid-type new surfactant, N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), were examined by means of pK(a), surface tension, light scattering and fluorescence measurements. The dissociation state of C12HEA-Glu was changed by varying pH of the aqueous solution. The critical micelle concentration (cmc) of aqueous solution of C12HEA-Glu was lowest at pH 5.6 and the cmc increased with decreasing pH. The aggregation number of C12HEA-Glu micelles was largest at pH 5.6 and decreased with decreasing pH. The surface tension-concentration curve for C12HEA-Glu in water (non-buffered solution) showed a minimum. This is considered to be due to the coexistence of a trace species and a main species of C12HEA-Glu with various dissociation states since the pH of aqueous solution of C12HEA-Glu changes with the concentration of C12HEA-Glu. The micropolarity in the micelles of C12HEA-Glu was almost independent of pH, while the microfluidity in the micelles increased with increasing pH.