Synthetic peptides as receptors in affinity sensors: a feasibility study

A relatively simple method for immobilizing synthetic peptides as a receptor onto a gold surface using the self-assembling monolayer (SAM) technique has been investigated. A synthetic peptide with an amino acid sequence similar to the 9-21 gD sequence of herpes simplex virus type 1 was modified with an alkylthiol chain and adsorbed in combination with an alkylthiol chain without peptide according to the SAM procedures. The resulting self-assembled receptor layers (SARs) were able to specifically interact with a monoclonal antibody directed against the 9-21 gD peptide. Binding studies monitored with a surface plasmon resonance setup showed that the response to the antibody depended on the composition of the SAR; a maximum response was reached at approximately 3 mol% peptide coverage. The response itself exceeded the value obtained from passive adsorption of the antibodies under similar conditions, indicating that the formed antibody layer is highly oriented. The equilibrium binding properties of the immobilized receptor molecules were found to be identical to those found when the immobilized antibodies interacted with the receptor molecule. The presence of a hydrophobic moiety in the alkylthiol derivates contributes to the ordering of the monolayer: a less specific interaction occurred when SARs without hydrophobic moiety were used.