Energy-filtered cryotransmission electron microscopy of liposomes prepared from human stratum corneum lipids.

We used cryo-TEM to examine the morphology of vesicles formed from lipids of the human stratum corneum (hSC). Human stratum corneum lipid liposomes (hSCLLs) were prepared in buffer at various pH values, using different preparation methods (film method, extrusion, ultrasonication, detergent dialysis). The morphology of hSCLLs at pH 7.4 differed markedly from that of liposomes formed by phospholipids, showing folds, stacks and membrane thickening. At pH 5.0, corresponding to natural conditions at the skin surface, membrane structures are essentially the same as those prepared at pH 7.4. Sharp edges in hSCLLs, branching membranes and stable membrane stacks were explained by the presence of ceramides, the major components and structural elements of human stratum corneum lipids (hSCLs). Thickened areas in the membranes may be caused by the local accumulation of triacylglycerols and cholesterol esters in the hydrophobic interior of the bilayer.