Cleansing Mechanisms and Efficacy on Artificial Skin.

A systematic study on the mechanisms of cleansing artificial skin by solutions of widely used in personal care surfactants disodium laureth sulfosuccinate (DSLSS), sodium laureth sulfate (SLES), sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB), and coco glucoside (CG), is presented. The systematic characterization of soil removal from artificial skin revealed two primary cleansing mechanisms: emulsification and roll-up. Emulsification occurs in systems with very low interfacial tension, such as sebum in SLES solutions, while dimethicone soil was only removed by roll-up. The roll-up effectiveness depends on the surfactant's interfacial activity and its adsorption on the soiled surface. Thus, the strong adsorption of DTAB on the skin leads to dimethicone roll-up at a relatively high interfacial tension of 11 mN/m. The anionic and nonionic surfactants adsorbed less at the artificial skin surface, and the oil/water interfacial tension value lowering below 5 mN/m is necessary for the roll-up to occur. Nonionic CG removed dimethicone at a lower concentration than ionic surfactants. Combining CG with ionic surfactants improved cleaning at lower total concentrations. Surfactant mixtures are used to formulate simple cleansing formulations, whose performance is also investigated by the developed in vitro approach. The results obtained allow for a good rating of the formulations, which correlates well with the performance of the surfactant mixtures and their interfacial activity.