AFM Study of Lipid Monolayers:  III. Phase Behavior of Ceramides, Cholesterol and Fatty Acids

Abstract

The outer part of the skin, stratum corneum, is essential to the skin's barrier function. Monolayer and bulk phase behavior of stratum corneum model lipids have thus been studied. Domain formation in Langmuir-Blodgett monolayers of synthetic ceramides (C16CerIII and C24CerIII), cholesterol, and free fatty acids (lignoceric acid, C24:0, and palmitic acid, C16:0) were investigated by atomic force microscopy. Binary, ternary, and more complex lipid mixtures were examined. It was shown that small amounts of ceramide are miscible in a cholesterol-rich phase with the miscibility dependent upon the ceramide chain length. Two phases are formed at low and intermediate cholesterol concentrations. In the ceramidecholesterol monolayers, very small rectangular-shaped ceramide domains thought to be two-dimensional single ceramide crystals are formed. Small domains were also found in more complex mixtures where the fatty acid is miscible in the ceramide phase, although these domains were not as regular in shape. Binary ceramide-cholesterol as well as ternary ceramide-cholesterol-lignoceric acid bulk mixtures were also studied by X-ray diffraction. The bulk lipid miscibility is consistent with the monolayer results.

Chemical Mapping of Ceramide Distribution in Sphingomyelin-Rich Domains in Monolayers

“…Langmuir-Blodgett monolayers comprised of ceramides, chol, and fatty acids that are used to model the skin strateum corneum composition exhibit ceramide-rich domains for a variety of lipid ratios. [29][30][31] Other studies have examined the influence of ceramide structure and surface pressure on the miscibility of mixed ceramide phosphatidylcholine monolayers. 32,33 The formation of a ceramide-enriched phase has been observed for chol/ceramide monolayers 34 and for SM monolayers at the air-water interface after treatment with SMase enzyme.…”

Influence of cholesterol on the structure of stratum corneum lipid model membrane

“…Although there are several studies focusing on the role of CHOL in the SC [6][7][8][9], the influence of CHOL on the SC lipid membrane structure still requires a complete elucidation.…”

Thermodynamic studies of bovine lung surfactant extract mixing with cholesterol and its palmitate derivative

“…Cholesterol, an important constituent of all cell membranes [11,12], regulates rigidity and fluidity in monolayers and membranes [2]. It has drastic effects on the physicochemical properties of lipid systems, the mechanism of which has yet to be fully understood [8,13].…”