Skin barrier: Extraction and characterization of Stratum Corneum lipids
Abstract: The structure and dynamics of isolated Stratum Corneum lipids in different temperatures and hydration conditions was investigated using natural abundance 13 C NMR and X-ray scattering. In order to isolate the lipids a new extraction method was tested. The novel aspect of this method was its ability to extract more lipids from SC. This new method (referred to as Method II in-text) was further modified. The resulting method (Method III) was chosen as the method to follow during this project. These two methods were also compared (using 13 C NMR) to an extraction method used in a pre-study. The lipids obtained through Method III were characterized with polarization transfer solid-state NMR and wide/small angle x-ray scattering. NMR studies showed that a greater amount of lipids in a rigid state were being extracted with the new extraction method. These studies also showed that hydration has a clear effect on lipid mobility at temperatures of 32 ˚C. In the dry state there is low mobility, while upon full hydration, a fraction of lipids are in a mobile state coexist with solid lipids. SAXS studies showed that SC lipids form two types of lamellar phases, one with a lamellar repeat distance of ~144 Å in dry and hydrated conditions, while another with a repeat distance of ~71Å in dry conditions and ~68 Å in hydrated conditions. In the solid fraction of SC lipids, the hydrophobic chain adopts hexagonal packing, as detected with WAXS.
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