Lipid bilayers supported on bare and modified gold – Formation, characterization and relevance of lipid rafts

Abstract

Supported lipid bilayers (SLB) comprise a very important set of model systems of biomembranes. In particular, they can be prepared on metallic surfaces such as gold electrodes, which allow a number of electrochemical studies and applications that could not be undertaken with other types of model systems, such as liposome suspensions. Also of special relevance is lipid bilayer composition, especially those combinations of lipids which permit the formation of biologically relevant membrane domains such as lipid rafts. Indeed, membrane domain organization is a crucial feature concerning not only the biophysical properties of the bilayer itself, but also the behavior and bioactivity of membrane-interacting biomolecules. In spite of its relevance, the presence of bilayer domains has not been central in many investigations involving lipid bilayers supported on conductive surfaces. Moreover, air exposed gold surface is hydrophobic, which is not ideally suitable to establish a proper interaction with the lipids polar head group. To overcome such limitation different strategies may be adopted, encompassing the fine tuning of the buffer conditions and previous surface modification by hydrophilic self-assembled monolayer (SAM) or thiolipids. This review will be focused on the formation and characterization of SLB and lipid rafts on gold substrates, illustrating the range of applications of such platforms, with examples of the study of electroactive molecules and the development of new biosensing interfaces.