New Water Soluble Lauroyl Lysine Derivative and Its Unique Physicochemical Properties for Cosmetics Applications

Abstract

N^ϵ-lauroyl lysine is an organic powder that is sparingly soluble in many kinds of cosmetic media. It is well known as a beneficial ingredient in various cosmetic applications; its excellent lubricity, water-repellency and non-greasy emolliency make it an ideal ingredient especially for makeups. However, its use in liquid formulations has been restricted because its inherent hydro-phobicity makes it difficult to disperse in aqueous media. We developed derivatives of N^ϵ-lauroyl lysine to find a compound soluble in water, and studied its characteristics as a cosmetic ingredient. New bis (N^ϵ-lauroyl lysine) derivatives, which have gemini-type surfactant structures, composed of two N^ϵ-lauroyl lysines linked by alkylene chains of various lengths, were synthesized, and their properties in aqueous media were examined. We observed that a compound with an alkylene chain length of C10 (labeled GE-10-LL) formed hydrogel structured by a three-dimensional nanofiber network over a pH range of 5.0-7.0. Fourier transform infrared spectroscopy measurements revealed that GE-10-LL worked as a low molecular gelator, resulting in the formation of self-assembled nanofibers through hydrogen bonding. Additionally, GE-10-LL was observed to be an effective foam booster for various foaming surfactants, and to be a sensory modifier with beneficial characteristics of the original N^ϵ-lauroyl lysine. In addition, GE-10-LL can easily form multilamellar vesicles (MLVs) with sterol ester. These MLVs can be prepared by stirring spontaneously, and they could encapsulate water-soluble active ingredients. We measured the penetration of MLVs into the stratum corneum using in vivo confocal Raman spectroscopy.