Stratum corneum lipid phase transitions and water barrier properties

Abstract

In mammals, the outer skin layer, the stratum corneum, is the ultimate barrier to water loss. In order to relate barrier function to stratum corneum structure, samples from porcine skin were investigated by using differential scanning calorimetry (DSC), infrared (IR) spectroscopy, and water permeability techniques. Results of DSC and IR studies show that stratum corneum lipids undergo thermal transitions between 60 and 80 degrees C similar to lipid thermotropic transitions seen in a variety of synthetic and biological membranes. Results of water flux experiments performed under conditions similar to those of the DSC and IR studies show an abrupt change in permeability at about 70 degrees C. At low temperatures, water flux values are similar to those obtained for human skin in vivo, yielding an activation energy of 17 kcal/mol, in excellent agreement with values obtained for water flux through a variety of lipid biomembranes. In contrast, at temperatures above about 70 degrees C, water flux is characterized by an activation energy only slightly higher than that of free diffusion, suggesting that the stratum corneum offers little diffusional resistance under these conditions. These combined results suggest that increased disorder in stratum corneum lipid structure, brought about by thermotropic transitions, results in dramatically altered diffusional resistance of this tissue to water flux. Thus, as found for numerous biological membranes, water flux and lipid order in porcine stratum corneum are inversely related.

Effect of Terpenes on the Skin Permeation of Lomerizine Dihydrochloride

“…Normally, hydrocarbons within the lipid domain of the SC below their transition temperature exist in a trans conformation. When the lipid domain becomes fluidized by thermal induction (46) and/or by treatment with chemical enhancer(s), an increase in the wavenumber of CH2 frequency would occur due to increased motional freedom and numbers of gauche conformers of lipid alkyl chains (47). Therefore, this increased lipid fluidity after combination treatment with terpenes and PG might be responsible for the enhanced permeability of LOM through hairless mouse skin.…”

Percutaneous Penetration Modifiers and Formulation Effects: Thermal and Spectral Analyses

“…Therefore, the objective of this paper was to investigate molecular changes in stratum corneum after treatment with different formulations of laurocapram, N-0915, DMBIS, DMMCBI and TBDOC using the two analytical methods of DSC and ATR-FTIR that provide independent yet complementary information regarding the interaction of enhancer/retardants within the SC (12,13). Though there are reports of DEET affecting SC when used as enhancer to increase the permeation of drugs (14), in our previous study (3), DEET was merely used as a model permeant to evaluate the permeation effects of penetration modifier formulations.…”

Phenotypic flexibility in cutaneous water loss and lipids of the stratum corneum

“…In the SC of mammals, ceramides account for as much as 50% of the total lipids (Raith and Neubert, 2000). From work mostly on mammals, but also a few domestic species of birds, evidence has accumulated that the SC forms the barrier to water vapor diffusion from the animal to the environment (Blank, 1953;Blank et al, 1984;Golden et al, 1987;Warner et al, 1988;Elias and Menon, 1991;Peltonen et al, 2000). Haugen et al (2003) have shown that free fatty acids, cholesterol and ceramides are the major constituents of SC in wild larks (skylarks, woodlarks, hoopoe larks and Dunn's larks) from mesic, semi-arid and arid environments.…”