Covalent coupling of immunoglobulin G to self-assembled monolayers as a method for immobilizing the interfacial-recognition layer of a surface plasmon resonance immunosensor

Protocols have been developed for the random and site-directed covalent coupling of immunoglobulin G [anti-hIgG] [IgG] to silver surfaces modified with a self-assembled monolayer [SAM] of thioctic acid, mercaptopropionic acid [MPA], l-cysteine or 4-aminothiophenol [PATP]. A surface plasmon resonance [SPR] immunosensor fabricated with a more ordered and hydrophilic IgG–SAM–silver interfacial layer, demonstrates an increased ability for performing sensitive and selective assay of human immunoglobulin G [hIgG] compared with a device fabricated with a physically-adsorbed IgG–silver interfacial-layer due to reduced levels of non-specific binding. Detection limits [D L] for hIgG from serum down to 6 μg/ml (40n m) and assay sensitivities up to 0.24 ng hIgG/mm 2/n m are reported.