Abstract:

To better understand the molecular mechanism of surfactant-induced skin damage and skin protection, human （skin endogenous）, exogenous substances （irritant and active ingredient against irritant）, and the interaction between them need to be explored simultaneously. However, there are few reports in real-time of the mechanism at molecular level on humans. Confocal Raman spectroscopy allows such investigation with in vivo, real-time, non-invasive analysis of both substances （endogenous or exogenous） in stratum corneum （SC） and the structure of SC. In this study, the relative amount and depth of transdermal absorption of sodium dodecyl sulfate （SDS） chosen as surfactant representative, and the changes in relative content and structure of skin lipids upon SDS invasion were measured qualitatively and semi-quantitatively by scanning volunteers’ skin of volar forearm at the depth of 0-12 μm with confocal Roman spectrometer. It showed that SDS was absorbed in SC, causing its lipid loss and lipid order reduction. The evidence that the amount and depth of irritant are two main factors affecting the extent of stimulation in skin was provided based on human data for the first time. The third factor, which could enhance SDS-induced barrier damage called the “conduction network of stimuli” was found in humans for the first time. The results of skin interior studied by Raman spectroscopy, combined with other techniques, including 3D skin model, Skin Surface Analyzer etc., all were in good agreement, which came to the molecular mechanism of SDS-induced skin/barrier damage and skin protection of what happened in the real world. The proposals were confirmed by the efficacy of surfactant antagonist called ASF thus designed by the fact that compared with the absence of antagonist, the damage to the skin barrier function caused by SDS could be reduced efficiently.

Key words: in vivo study on molecular mechanism of skin irritation by surfactant, skin protection, confocal Raman spectroscopy