Self-assembled layer of thiolated protein G as an immunosensor scaffold.

In this study, our goal was to produce a self-assembled layer on a gold electrode that would enable the capture of antibodies orientated for maximum binding to their specific antigen in an immunosensor. To achieve this, the amine groups from lysine residues in protein G were initially converted to thiol groups with 2-iminothiolane. The high affinity of thiols for a gold surface facilitates the direct formation of a self-assembled protein G layer. Following this, the coated gold electrode was exposed to a solution of capture antibody (mAb1) so that these antibodies could attach to the protein G layer through their nonantigenic regions, leaving antigen binding sites available with minimal steric hindrance for binding of target analyte. A comparative study between this method and the more conventional strategy of covalently attaching a layer of nonthiolated protein G on an alkanethiol self-assembled monolayer-coated gold electrode has been performed. Based on a reduced preparation time, and an enhanced capacity for immobilized capture antibody to bind its target analyte due to a more favorable orientation, the layer of thiolated protein G was found to be a more suitable backbone for an electrochemical immunosensor.