Formation, stability, and mobility of one-dimensional lipid Bilayers on polysilicon nanowires
ABSTRACT Curved lipid membranes are ubiquitous in living systems and play an important role in many biological processes. To understand how curvature and lipid composition affect membrane formation and fluidity, we have assembled and studied mixed 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) supported lipid bilayers on amorphous silicon nanowires grown around carbon nanotube cores with controlled wire diameters ranging from 20 to 200 nm. We found that lipid vesicles fused onto nanowire substrates and formed continuous bilayers for all DOPC-DOPE mixtures tested (with the DOPE content of up to 30%). Our measurements demonstrate that nanowire-supported bilayers are mobile, exhibit fast recovery after photobleaching, and have a low concentration of defects. Lipid diffusion coefficients in these high-curvature tubular membranes are comparable to the values reported for flat supported bilayers and increase slightly with decreasing nanowire diameter. A free space diffusion model adequately describes the effect of bilayer curvature on the lipid mobility for nanowire substrates with diameters greater than 50 nm, but shows significant deviations from the experimental values for smaller diameter nanowires.
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ABSTRACT: Cell membranes contain a variety of lipids and functional proteins that offer active platforms that organize the membrane components into functional assemblies and perform biologically important reactions. The dynamic and complex nature of the membranes makes them attractive materials, but at the same time, researchers report substantial experimental uncertainty in controlling the membrane reactions and extracting valuable information. The fascinating new structures and properties of nanomaterials could be utilized in addressing aforementioned issues, and the design and synthesis of lipid-nanostructure hybrids could be beneficial to the research areas in lipid-membrane biotechnology and nanobiotechnology. These hybrid structures possess dimensions that are comparable to that of biological molecules and structures and physicochemical properties that arise from both lipids and nanomaterials. Therefore, lipid-nanostructure hybrids offer additional options for control of the synthesized structures, provide new insight in understanding nanostructures and biological systems and allow the mimicking of functional subcellular membrane components and monitoring of the membrane-associated reactions in a highly sensitive and controllable manner. In this review, we present recent advances in the synthesis of various lipid-nanostructure hybrids and the application of these structures in biotechnology and nanotechnology. We further describe the scientific and practical applications of lipid-nanostructure hybrids for detecting membrane-targeting molecules, interfacing nanostructures with live cells and creating membrane-mimicking platforms to investigate various intercellular processes.05/2013; 5(5). DOI:10.1038/am.2013.13
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ABSTRACT: Many processes in life are based on ion currents and membrane voltages controlled by a sophisticated and diverse family of membrane proteins (ion channels), which are comparable in size to the most advanced nanoelectronic components currently under development. Here we demonstrate an electrical assay of individual ion channel activity by measuring the dynamic opening and closing of the ion channel nanopores using single-walled carbon nanotubes (SWNTs). Two canonical dynamic ion channels (gramicidin A (gA) and alamethicin) and one static biological nanopore (α-hemolysin (α-HL)) were successfully incorporated into supported lipid bilayers (SLBs, an artificial cell membrane), which in turn were interfaced to the carbon nanotubes through a variety of polymer-cushion surface functionalization schemes. The ion channel current directly charges the quantum capacitance of a single nanotube in a network of purified semiconducting nanotubes. This work forms the foundation for a scalable, massively parallel architecture of 1d nanoelectronic devices interrogating electrophysiology at the single ion channel level.
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ABSTRACT: Sensing and manipulating living cells using vertical nanowire devices requires a complete understanding of cell behavior on these substrates. Changes in cell function and phenotype are often triggered by events taking place at the plasma membrane, the properties of which are influenced by local curvature. The nanowire topography can therefore be expected to greatly affect the cell membrane, emphasizing the importance of studying membranes on vertical nanowire arrays. Here, we used supported phospholipid bilayers as a model for bio-membranes. We demonstrate the formation of fluid supported bilayers on vertical nanowire forests using self-assembly from vesicles in solution. The bilayers were found to follow the contours of the nanowires to form continuous and locally highly curved model membranes. Distinct from standard flat supported lipid bilayers, the high aspect ratio of the nanowires results in a large bilayer surface available for the immobilization and study of biomolecules. We used these bilayers to bind a membrane-anchored protein, as well as tethered vesicles on the nanowire substrate. The nanowire-bilayer platform shown here can be expanded from fundamental studies of lipid membranes on controlled curvature substrates, to the development of innovative membrane-based nanosensors.Nano Letters 06/2014; 14(8). DOI:10.1021/nl500926y · 12.94 Impact Factor