Method for Fabricating Supported Bilayer Lipid Membranes on Gold

Abstract

The paper describes the synthesis of surfaces based on self-assembled monolayers (SAMs) of alkanethiolates on gold that were designed to support the adsorption of bilayer lipid membranes, and the feasibility of using these surfaces for making high-density arrays (HDAs) of membranes. The synthesis involved (i) the formation of SAMs of 16-mercaptohexadecanoic acid (MHA) on gold; (ii) the activation of the carboxylic acid groups to interchain anhydrides; (iii) the treatment of the reactive surfaces with Brij-76 (C18H37(OCH2CH2)n-10OH) (1) or Brij-76-amine (2) (C18H37(OCH2CH2)n-10NH2); and (iv) the formation of supported membranes by incubation or printing of the lipids. The oligo(ethylene glycol) moiety of the anchor lipid provides a hydrophilic spacer between the surface and the adsorbed lipid to enable the incorporation of membrane-spanning proteins with extramembrane domains. Data from infrared spectroscopy confirmed the coupling of 2 to the surface through the formation of peptide bonds. Ellipsometric measurements showed an increase of ∼15 Å in the thickness of the SAM after coupling to 2; this observation suggests that ∼25% of the carboxylic acid groups of the MHA-SAM are derivatized with Brij groups. The yields for coupling of 1 were ∼40% of that observed for 2. Experiments using surface plasmon resonance (SPR) were consistent with the binding of lipid bilayers to the Brij-derivatized surface, although alternative structures for the supported lipids cannot be ruled out; by contrast, SAMs of hexadecanethiolate on gold were observed to bind lipid monolayers. Biospecific binding of neutravidin was observed on supported membranes incorporating biotinylated lipids. HDAs of lipids were made by printing lipids onto the Brij-derivatized surfaces using a quill-pin printer. Fluorescence microscopy indicated that the printed lipids remained confined to the printed areas; these observations demonstrate the applicability of using commercial HDA printers for generating high-density membrane arrays on the Brij-modified surfaces.