Preparation of tethered-type supported lipid bilayer using water-soluble silane coupling agent

Supported lipid bilayer (SLB) is one of the cell membrane model systems used to investigate the functions of lipids and membrane proteins. Tethered-type SLB (t-SLB) is a unique platform for controlling the distance and interaction between SLB and its substrate. In this study, we used a water-soluble silane coupling agent to modify a SiO2/Si substrate, keeping its surface roughness on the order of subnanometer, for the purpose of t-SLB fabrication. We modified the SiO2/Si substrate using carboxyethylsilanetriol (CEST) to terminate the surface with a carboxy group. The surface roughness was kept at ∼0.15 nm (rms) after the CEST modification and following streptavidin conjugation. We prepared t-SLB that contained biotinylated lipids on the streptavidin-modified substrate using the vesicle fusion method and osmotic stimulation. Atomic force microscope observation and fluorescence recovery after photobleaching measurement showed that t-SLB was as flat as the SiO2/Si substrate and had approximately 20% smaller diffusion coefficient than non-tethered SLB.