Effects of Oleic Acid on Stratum Corneum Lipids in Langmuir Monolayers

Abstract

The mechanism of oleic acid (OA) as a transdermal permeation enhancer has long been debated. In this study, the interaction between OA and stratum corneum (SC) lipids was investigated with an aqueous monolayer of model SC lipids. Different amount of OA was cospread with equal molar mixture of ceramide, cholesterol and palmitic acid at the air/water interface. The monolayer phase behavior was monitored through surface pressure-molecular area isotherms (π-A isotherms). With increasing OA concentration in the monolayer, the resultant films became more fluid and more compressible. OA also modified the domain structure in SC monolayers as visilized through Brewster Angle Microscope (BAM). The miscibility curve derived from π-A isotherms demonstrated the preferential interaction between OA and SC lipids. IRRAS measurements showed that OA mixed with ceramide and disordered its acyl chains. The acyl chain order of palmitic acid was also lowered by OA but to a lesser extent.