Fatty acids influence "solid" phase formation in models of stratum corneum intercellular membranes

Area of Science:

• Biophysics
• Dermatology
• Materials Science

Background:

• The stratum corneum (SC) provides skin barrier function via intercellular lipid membranes.
• SC lipids include ceramides (Cer), cholesterol, and free fatty acids (FFA) with unusually long chains.
• Previous work showed model membranes solidify at pH 5.2.

Purpose of the Study:

• To investigate how free fatty acid (FFA) chain length affects the phase behavior of stratum corneum (SC) model membranes.
• To understand the relationship between FFA chain length and lipid membrane properties relevant to skin barrier function.

Main Methods:

• Studied bovine brain ceramide (BBCer)/cholesterol/FFA dispersions using 2H NMR and FT-IR.
• Investigated FFA with linear saturated chains ranging from 14 to 22 carbons.
• Analyzed phase transitions, lipid mixing, and transition temperatures.

Main Results:

• Solid phase dominated FFA spectra at physiological temperature, regardless of chain length.
• Dispersions transitioned to liquid crystalline and then isotropic phases upon heating.
• Phase behavior, lipid mixing, and transition temperatures were strongly dependent on FFA chain length.

Conclusions:

• FFA chain length critically influences SC model membrane phase behavior and properties.
• A distribution of FFA chain lengths in the SC may be essential for maintaining fluid and solid lipid domains necessary for skin barrier function.