Abstract
Supported phospholipid membrane patches stabilized on graphene surfaces have shown potential in sensor device functionalization, including biosensors and biocatalysis. Lipid dip-pen nanolithography (L-DPN) is a method useful in generating supported membrane structures that maintain lipid functionality, such as exhibiting specific interactions with protein molecules. Here, we have integrated L-DPN, atomic force microscopy, and coarse-grained molecular dynamics simulation methods to characterize the molecular properties of supported lipid membranes (SLMs) on graphene and graphene oxide supports. We observed substantial differences in the topologies of the stabilized lipid structures depending on the nature of the surface (polar graphene oxide vs nonpolar graphene). Furthermore, the addition of water to SLM systems resulted in large-scale reorganization of the lipid structures, with measurable effects on lipid lateral mobility within the supported membranes. We also observed reduced lipid ordering within the supported structures relative to free-standing lipid bilayers, attributed to the strong hydrophobic interactions between the lipids and support. Together, our results provide insight into the molecular effects of graphene and graphene oxide surfaces on lipid bilayer membranes. This will be important in the design of these surfaces for applications such as biosensor devices.
Highlights
Article lipid patches generally takes place in air
Previous studies have shown that the formation of stable lipid structures, such as multilayered lipid membranes, on graphene, silicon dioxide, and other substrates can be generated by LDPN and are influenced by surface morphology and experimental conditions.[13,38−40] Here, we used CG-molecular dynamics (MD) simulations to investigate the molecular details of lipid interactions with pristine graphene and with graphene oxide surfaces
The simulated systems were constructed to match the experimental conditions used during Lipid dip-pen nanolithography (L-Dip-pen nanolithography (DPN)) and atomic force microscope (AFM) studies as well as currently possible
Summary
The structures will usually be transferred into liquid only after the lithographic step is completed, as most applications take place in liquid phase This suggests that the lipid structures may rearrange, and different structural models have been proposed for the molecular organization of the lipid membrane in air and water and on surfaces with varying hydrophilicity.[13,28−30]. Recent studies have focused on parametrizing models of various support materials, for example, graphite, to more accurately represent interactions of organic molecules, such as long-chain alkanes, with the support.[37] These models were shown to reproduce phase transitions and molecular organization of organic molecules on the surface, in line with experimental data.[31,37]
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