Fusion of Small Unilamellar Lipid Vesicles to Alkanethiol and Thiolipid Self-Assembled Monolayers on Gold

Abstract

Adsorption of a monolayer of dimyristoyl- L -α-phosphatidylcholine from dispersions of small unilamellar vesicles onto hydrophobic surfaces was investigated by means of a combined surface plasmon resonance spectroscopy/impedance spectroscopy/cyclic voltammetry setup. The hydrophobic surfaces were prepared by assembling alkanethiols or a thiolipid onto gold surfaces. The kinetics of the monolayer formation were followed using time-dependent surface plasmon resonance spectroscopy in combination with time-dependent impedance spectroscopy and showed remarkable differences depending on the composition of the proximal monolayer. The formation of the lipid monolayer on these assemblies was complete after an adsorption time of ∼6000−10000 s. We observed differences in the thickness and capacitance of the lipid monolayer depending on the underlying thiol monolayer. The expected thickness and capacitance were obtained using long chain thiols or the thiolipid for the proximal monolayer. Electrochemical measurements of electron transfer rates indicate that the lipid monolayer improves the blocking properties of the assembled alkanethiols and thiolipid.