Assembly of Lipid Membrane in Salt Solution and Structure Transformation Induced by Electric Field

The nanoscale organisation and transformation of self-assembled lipid membranes is central to the biological function of cells analysis and bionic structure construction as well as the biosensors research. While lots of work have focused on chemical interactions of component within the membrane, limited results address the impact of a trans-membrane potential on the molecular behaviour of the lipids and the related effects, especially in physiological media solutions. Here, in a salt solution that was isotonic to the physiological medium and utilizing a combination of atomic force microscopy (AFM) and fluorescence recovery after photobleaching (FRAP) techniques, the nanoscale molecular arrangement, assemble of neutral and charged lipids at the surface of highly ordered pyrolytic graphite (HOPG) and the its structure transition under electrical potentials were studied. The results showed that these lipids were spread on HOPG in the form of monolayers at gel-phase because of the hydrophobic effect between substrate and lipid legs at room temperature. These lipids further assembled to form nanoscale semi- micellar structures and exhibited the corrugations morphology in AFM images. When a moderate electric field (+/- 1.0 V) was applied on HOPG substrate, it was found to play a major role in inducing the arrangement of lipid molecules and structural transformation, while interfacial solvation forces and ion effects played a minor role. This work provided reference for the simulation of bioelectrochemical devices and the development of phospholipid- based macromolecule laboratory chips.