Biologically addressable monolayer structures formed by templates of sulfur-bearing molecules

Abstract

We demonstrate that the combined application of Langmuir-Blodgett and self-assembly techniques allows the fabrication of patterns with contrasting surface properties on gold substrates. The process is monitored using fluorescence microscopy and surface plasmon spectroscopy and microscopy. These structures are suitable for the investigation of biochemical processes at surfaces and in ultrathin films. Two examples of such processes are shown. In the first example, the structures are addressed through the binding of a monoclonal antibody to a peptide. This demonstrates the formation of self-assembled monolayers by cysteine-bearing peptides on gold, and the directed binding of proteins to the structured layers. A high contrast between specific and unspecific binding of proteins is observed by the patterned presentation of antigens. Such films possess considerable potential for the design of multichannel sensor devices. In the second example, a structured phospholipid layer is produced by controlled self-assembly from vesicle solution. The structures created--areas of phospholipid bilayer, surrounded by a matrix of phospholipid monolayer--allow formation of a supported bilayer which is robust and strongly bound to the gold support, with small areas of free-standing bilayer which very closely resemble a phospholipid cell membrane.

Detection of supported lipid layers with the acoustic Love waveguide device: application to biosensors

“…The aim of this work was initially to apply simple and well characterised chemistry on the device surface in order to study the sensitivity of the sensor to mass loading in presence of liquid and the ability of the acoustic signal to follow the reverse process of the formation and desorption of a mass layer on and from the device surface. The in situ formation of lipid layers on the device surface has been chosen as a model system, since supported lipid layers have been studied and characterised extensively by many groups [5-101. It has been shown that a lipid mono-or bilayer will be formed spontaneously on a hydrophobic or hydrophilic surface, respectively, if the corresponding surface is exposed to an aqueous solution of vesicles of phospholipids [5][6][7][8][9]. In order to control the wetting properties of the device surface and produce a well-defined hydrophobic or hydrophilic surface, the self-assembly (SA) technique has been applied.…”

“…The lipid layer is stable in aqueous media, but can be removed using detergents to give the original surface. The self assembly of the thiol and the subsequent formation and removal of the lipid layer have been studied and characterised using optical techniques [6,9]. Thus, the lipid layer provides a good model system for relating the acoustic response to the deposited mass and for checking the potential of reusing the device after regeneration of the surface.…”

“…The following thiols were used: mercaptoundecanoi (HS(CH2)IIOH), synthesized as previously described [6], and dodecanethiol (HS(CH2)IICH3), purchased from Aldrich.…”

“…The peptides C(NANP)6Y and C(NANP)3Y and the monoclonal antibody E9 were synthesised and prepared, respectively, as described elsewhere [6,11]. Solutions of 3.7×10 -~ M of C(NANP)6Y and C(NANP)3Y and 3.5 x 10 -7 M of E9 were prepared in PBS buffer.…”

“…Several groups have shown that if a highly hydrophobic surface consisting of long hydrocarbon chains is brought into contact with an aqueous solution containing phospholipid vesicles, the vesicles spontaneously fuse to the surface and form a lipid monolayer [7,9]. It has also been shown that if the surface consists of densely arranged hydroxyl groups, its exposure to a vesicle dispersion will lead to the formation of a well-defined supported phospholipid bilayer [5,6].…”