Biomimetic membrane rafts stably supported on unmodified gold

Abstract

The formation of lipid bilayers on bare gold containing gel/fluid and liquid disordered/liquid ordered domains (lipid rafts), essential for the functioning of biological membranes, is reported here for the first time. Such binary and ternary lipid mixtures deposited on gold are improved biomimetic platforms. However, gold's hydrophobic nature has been an obstacle for direct deposition, and most studies rely on previous modification of its surface. In this work, lipid mixtures were deposited under different experimental conditions, including those commonly used for other solid supports such as mica, which are known to yield planar and organized bilayers. Atomic force microscopy imaging was used to study the topography of the lipid films at the nanoscale. The coverage, continuity and packing were addressed by ellipsometry and cyclic voltammetry, taking advantage of gold optical/electrical properties. A high quality bilayer displaying well organized lipid rafts is obtained by small or large unilamellar vesicle fusion in 10 mM Hepes buffer without added salt, while the presence of NaCl inhibits the formation of a lipid bilayer and leads to tubular structures. The raft-containing bilayer is stable over a wide range of potential sweep, enabling the development of new lipid raft based biosensing interfaces.