Lipid bilayer is a fundamental structure of plasma membranes, and plays important roles for various membrane reactions such as the transport of material, energy, and information. Graphene oxide (GO) has a unique fluorescence quenching property, and applied to biosensing recently. In this study, we formed multi-component supported lipid bilayer on GO, and observed the distribution of domains and evaluated the fluidity. We formed the SLB comprising of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), or of DOPC and polyethylene glycol-1,2-disterol-sn-glycero-3-phosphoethanolamine (PEG-DSPE) by the vesicle fusion method. The GO suspension was prepared by the modified Hummer’s method, and was dropcast on a thermally oxidized SiO2/Si substrate In the DPPC+DOPC (1:1)-SLB, phase separation between DPPC-rich gel phase and DOPC-rich liquid crystalline (Lα) phase occurs at 25 °C. The former is observed higher in AFM topography and darker in fluorescence image than the latter. Atomic force microscope (AFM) topography show that the gel-domains selectively existed on the GO region and that the surrounding SiO2 region was free from the gel-domains. Fluorescence images also showed that the dark gel-domains were not observed in the vicinity of GO while the gel-domains existed in the SiO2 region away from GO. In the SLB comprising of DOPC and PEG-DSPE, PEG-DSPE-rich domains appeared at the PEG-DSPE concentration higher than 5 %, also preferentially on GO. We measured the diffusion coefficient (D) of the SLB on GO by single particle tracking (SPT) using a quantum dot (Qdot) as a fluorescence probe. Fluorescence dyes are not available under the quenching effect of GO, but Qdot was bright enough for SPT measurement on GO. The values of D were 2.64 μm2/s at PEG-DSPE 2.5%, 2.45 μm2/s at 5.0%, and 1.21 μm2/s at 7.5%. Lateral mobility of lipids decreased with the concentration of PEG-DSPE. These results indicate that less-fluid lipid components were concentrated on GO, and more fluid components distributed in the SLB around GO.

Multi-component lipid bilayer membranes on GO: Domain distribution and fluidity evaluation

255th National Meeting (2018)

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