Influence of Substrate Hydrophilicity on Structural Properties of Supported Lipid Systems on Graphene, Graphene Oxides, and Silica

Abstract

Pristine graphene, a range of graphene oxides, and silica substrates were used to investigate the effect of surface hydrophilicity on supported lipid bilayers by means of all-atom molecular dynamics simulations. Supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers were found in close-contact conformations with hydrophilic substrates with as low as 5% oxidation level, while self-assembled monolayers occur on pure hydrophobic graphene only. Lipids and water at the surface undergo large redistribution to maintain the stability of the supported bilayers. Deposition of bicelles on increasingly hydrophilic substrates shows the continuous process of reshaping of the supported system and makes intermediate stages between self-assembled monolayers and supported bilayers. The bilayer thickness changes with hydrophilicity in a complex manner, while the number of water molecules per lipid in the hydration layer increases together with hydrophilicity.

Kinetics of Ganglioside-Rich Supported Lipid Bilayer Formation with Tracer Vesicle Fluorescence Imaging

“…A supported lipid bilayer (SLB) is a 5 nm thick lipid membrane formed on a solid substrate such as silica, mica, quartz, etc. − Typically, a water layer of ∼10–20 Å exists between the support and the lower lipid leaflet of an SLB, and the lipids in SLBs have lateral mobility with diffusion coefficient ranging from 0.11 to 4 μm 2 /s. ,− SLBs also possess transversal mobility between the lower and upper leaflets (interleaflet flip-flop). , The group of McConnell introduced the fabrication of SLBs upon rupturing of unilamellar lipid vesicles on a solid support and has shown the applications of SLBs in cell–cell recognition/communication upon contact of their membranes. − Thereafter, the vesicle rupturing method has been widely employed to form SLBs composed of simple zwitterionic phospholipids, composed of binary − or ternary lipid , compositions, and even reconstituted with membrane proteins. − These cell-membrane-mimicking SLBs are applied for studying the function and lateral distribution of membrane proteins, ,, receptor-binding of viral proteins and bacterial toxins, , multivalent binding of nanoparticles and virions, − and other membrane processes. , …”