R. Sreij, C. Dargel and T. Hellweg
Keywords: characterization, Escin, DMPC
Summary:Lipid bilayer membranes are key objects in drug research in relation to interaction of drugs with membranes, membrane-bound receptors and drug targeting, penetration and permeation of cell membranes as well as the use of liposomes for drug-delivery. The design of new drugs requires therefore insights into the physical properties of lipid membranes. The function of membrane proteins depends on the lipid bilayer thickness and its properties. In the present contribution we study the properties of the lipid bilayer in model membrane systems in form of unilamellar vesicles (ULVs) consisting of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the presence of saponins. Saponins are a diverse class of natural, plant derived amphiphilic molecules with a peculiar molecular structure made of a hydrophobic scaffold and hydrophilic oligosaccharide chains. They have strong surface activity and are used as natural emulsifiers and foaming agents in food, pharmaceutical and other industries. Their incorporation into the membrane of living cells reduces the cholesterol bioaccessibility by displacement of cholesterol molecules from the bile salt micelles. Here, we use the nearly pure saponin Aescin. The effect of the Aescin incorporation into small unilamellar vesicles is studied by various techniques including small- and wide-angle X-ray scattering (S/WAXS), small-angle neutron scattering (SANS), dynamic light scattering (DLS), turbidity and differential scanning calorimetry (DSC). The comprehension of the interaction of saponins with the lipid membrane is crucial for understanding the properties of future drug delivery systems such as immune stimulating complex matrices (ISCOMs), being modern delivery systems for vaccines. Besides the phospholipid and cholesterol saponins, are the major component of these structures.