Imaging Characterization of Cluster-Induced Morphological Changes of a Model Cell Membrane

Understanding the activity of nanomaterials at the lipid bilayer surface can provide key information for the feasible design of functional bioactive agents. Herein, we used micro- and nanoscopic imaging techniques to evaluate the activity of nanometer-sized inorganic clusters and report that destruction of the lipid membrane is induced by a cluster-induced morphological change on the membrane surface. As model experiments, we used the Keggin-type polyoxometalate (POM) SiW₁₂O₄₀^4– for the inorganic cluster and a 1,2-dimyristoyl-<i>sn</i>-glycerol-3-phosphatidylcholine (DMPC) and egg phosphatidylcholine (EPC) bilayer for the cell membrane. Imaging experiments revealed vigorous desorption of the lipid bilayer from solid substrate by the formation of POM–lipid assembly through a supramolecular-type assembly process in which electrostatic and hydrophobic interactions between the POM and lipid determine the efficiency and dynamics of assembly formation and thereby determine lipid desorption. Furthermore, maximum efficiency of lipid desorption was found at the phase-transition temperature. This phase dependency was explained by the formation of a “leaky interface” between the gel and fluid domains, in which freedom in the conformational change of lipids during the formation of the POM–lipid assemblies becomes maximal