Electrochemical Properties of Lipid Membranes Self-Assembled from Bicelles

Abstract

Supported lipid membranes are widely used platforms which serve as simplified models of cell membranes. Among numerous methods used for preparation of planar lipid films, self-assembly of bicelles appears to be promising strategy. Therefore, in this paper we have examined the mechanism of formation and the electrochemical properties of lipid films deposited onto thioglucose-modified gold electrodes from bicellar mixtures. It was found that adsorption of the bicelles occurs by replacement of interfacial water and it leads to formation of a double bilayer structure on the electrode surface. The resulting lipid assembly contains numerous defects and pinholes which affect the permeability of the membrane for ions and water. Significant improvement in morphology and electrochemical characteristics is achieved upon freeze–thaw treatment of the deposited membrane. The lipid assembly is rearranged to single bilayer configuration with locally occurring patches of the second bilayer, and the number of pinholes is substantially decreased. Electrochemical characterization of the lipid membrane after freeze–thaw treatment demonstrated that its permeability for ions and water is significantly reduced, which was manifested by the relatively high value of the membrane resistance.

Physicochemical Characterization of Sparsely Tethered Bilayer Lipid Membranes: Structure of Submembrane Water and Nanomechanical Properties

“…These changes are consistent with the results obtained from ACV, where similar potential dependence was observed for differential capacitance. Similar range of the capacitances was also reported for floating bilayer lipid membranes with good insulating properties [26] …”

“…Similar range of the capacitances was also reported for floating bilayer lipid membranes with good insulating properties. [26] Integrity of the membrane and its morphology was verified using atomic force microscopy. Figure 4(A) illustrates the image of stBLM recorded at the potential of 0.2 V. It proves that DMPC/Cholesterol forms continuous film without visible defect sites.…”

Effect of Molecular Structure on Electrochemical Phase Behavior of Phospholipid Bilayers on Au(111)

“…Changes in the field across the membrane can result in changes in structure, for example, the reorientation of dipoles or even membrane breakdown at high fields, so the study of these changes is essential for understanding the function of the membrane. Electrochemical measurements provide a means to tune an electric field continuously over a similar range to that found in nature , and have demonstrated the effect of this field on monolayers for various lipids on mercury. − Further in situ structural studies, utilizing techniques such as atomic force microscopy, − scanning tunneling microscopy, , vibrational spectroscopy, ,,,− and neutron reflectivity ,, to investigate bilayers supported on or floating on gold electrodes, have shown changes in ensemble structure as the applied field is varied. Some studies have highlighted the role of lipid molecule structure on ensemble structure and response to the applied field; ,, others have focused on the interaction of peptides and proteins with a lipid bilayer and how charge controls their insertion. ,,− …”

Designing a Useful Lipid Raft Model Membrane for Electrochemical and Surface Analytical Studies

“…This behavior can be ascribed to electroporation. A lipid bilayer lifts from the surface of the electrode, while water accumulates in the region between the membrane and the solid substrate [70,71]. At most negative potentials it finally leads to a complete detachment of the membrane from a solid substrate, which is manifested by the overlapping of the curve with that obtained for a film-free Au (111) substrate (Figure 6).…”

“…The spectra were collected at the potential of −0.2 V vs. Ag|AgCl, which corresponds to the potential, at which the capacitance determined from ACV measurements displayed the minimum. At such a potential, the lipid bilayer is the most densely packed and stable [71]. Obtained spectra were fitted to the equivalent circuit, where R sol and R m represent the resistance of solution and membrane, respectively, while Q m and Q sp are constant phase elements of membrane and a thin layer of water as a spacer between the bilayer and Au (111) surface.…”