33568 Evaluating the mildness of glycinate-based cleanser through in vitro methodologies and computational modeling

Abstract

Facial cleansing is an important step of a skin care routine to remove unwanted dirt and excess oil. While a cleanser may effectively remove dirt, depending on the surfactant system, it may not necessarily be gentle on the skin. The mildness of a glycinate-based cleanser was determined by assessing the integrity of skin barrier through changes in the lipid organization and using dye penetration. Fourier transform infrared spectroscopy was used to evaluate lipid organization in the stratum corneum (SC) and showed that glycinate-based cleanser increased the height and area at wavelengths corresponding to lipid hydrocarbon chains, indicating significant lipid deposition in the SC compared with sodium lauryl ether sulfate (SLeS). However, dye penetration results showed that the glycinate-based cleanser had significantly lower dye penetration compared with SLeS and soap, indicating preserved barrier. Although lipid deposition was observed in the SC, the glycinate-based cleanser maintained the integrity of the skin barrier. To elucidate the origin of the mildness, the key ingredients in the formulation were evaluated by Dissipative Particle Dynamics (DPD) simulations and Small Angle X-Ray Scattering. Results showed that larger mixed surfactant vesicles that were formed in the polymer matrix were relatively immobile in comparison to the fast-moving small glycinate micelles without polymers. This reduced surfactant mobility provides a controlled release effect on the cleansing surfactants such that the concentration of surfactant in contact with the skin barrier is sufficiently low during the washing step. The polymers thereby play a key role in imparting mildness of the glycinate-based cleanser.