Lipid Membrane Formation by Vesicle Fusion on Silicon Dioxide Surfaces Modified with Alkyl Self-Assembled Monolayer Islands

Abstract

Using atomic force microscopy, we have investigated the formation of the dipalmitoylphosphatidylcholine (DPPC) membrane by the vesicle fusion method on SiO2 surfaces modified with self-assembled monolayer (SAM) islands of octadecyltrichlorosilane (OTS) with sizes comparable to those of the vesicles. OTS-SAM islands with various sizes and coverages can be constructed on the SiO2 surfaces prepared by thermal oxidation followed by partial hydroxylation in a H2O2/H2SO4 solution. When vesicles are sufficiently smaller than the SiO2 domains, DPPC bilayers and DPPC/OTS layers form on the SiO2 and OTS domains, respectively. However, the adhesion of larger vesicles onto SiO2 is prevented by the OTS islands; therefore only DPPC/OTS layers form without formation of DPPC bilayers on the SiO2 domains. On surfaces with domains on the scale of tens to hundreds of nanometers, the relative size between the hydrophilic domains and the vesicles becomes an important factor in the membrane formation by the fusion of vesicles.

Substrate Effects on the Formation Process, Structure and Physicochemical Properties of Supported Lipid Bilayers

“…The interaction between lipid bilayer membranes and solid substrates is a quite influential factor during the vesicle fusion processes shown in Figure 1, as well as other factors, like the lipid components [56,57] and the size of vesicles [58,59,60,61,62], the solute concentration in the solution [40,58] and temperature. At the early stage of SLB researches, adsorption states of vesicles and transformation processes to a planar membrane was characterized in situ with label-free methods, such as quartz crystal microbalance [63], ellipsometry [64,65], surface plasmon resonance [64] and AFM [66].…”

“…The transformation processes from vesicles to a SLB are strongly affected by the physical and chemical properties of the substrate surfaces, such as materials [40,59,60,63,67,82,83,84,85,86], chemical termination [25,26,62,63,87,88,89] and surface charges [54,90,91]. As a comprehensive parameter including several surface properties, the hydrophilicity of surfaces is useful to express the behavior of the vesicles on the surfaces.…”

Effects of Applied Voltage on the Size of Phase-Separated Domains in DMPS-DOPC Lipid Binary Bilayers Supported on SiO₂/Si Substrates

“…Vesicle suspensions were prepared through the following procedure [10] of TR-DPPE was evaporated onto the wall of a glass vial by bowing N 2 gas, and evacuated overnight; Secondly, the lipid mixtures were re-suspended in buffer solutions (10 mM HEPES, 150 mM KCl, pH 7.4 (NaOH)) with various CaCl 2 concentrations (0.001, 0.1, 1 100 mM) by vortexing moderately to prepare vesicle suspension with the total lipid concentration of 100 μM; Finally, the vesicle suspensions were agitated and sonicated, and they were fractured applying freeze-and-thaw cycles in liquid nitrogen three times, and extruded through a 100 nm polycarbonate filter 19 times at 45 °C. The sample was not exposed to the air during preparation.…”

Direct Stabilization of a Phospholipid Monolayer on H-Terminated Silicon

“…Typically, bilayers have been stabilized on oxidized silicon surfaces or polymers. [19][20][21][22][23][24][25][26] Stabilization of monolayers has always been a little bit more of a challenge. Successful studies are reported; however, the stabilization has always involved the formation of covalent bonding between the acryloyl-phospholipids and an intermediate acrylate modified silicon oxide surface or acrylated polymer.…”