Nanoscale fabrication of protein A on self-assembled monolayer and its application to surface plasmon resonance immunosensor

The fabrication of protein A film on self-assembled monolayer was done for the construction of immunosensor using surface plasmon resonance (SPR) measurement. The layer of heterobifunctional linker, N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) was self-assembled on the gold (Au) surface. Due to the succinimidyl functional group in SPDP to be reacted with amine (single bondNH2) group of protein A, the covalent immobilization of protein A was subsequently induced toward Au surface. The characteristics of film formation were investigated using SPR with respect to the various concentrations of SPDP and protein A. The optimal concentration for the film formation was found to be 0.1 mg/mL of SPDP and 0.1 mg/mL of protein A, respectively. The surface topography of protein A layer using atomic force microscopy showed that the heteromolecular layer was formed successfully. The antibody, anti-bovine serum albumin (BSA), was immobilized onto protein A layer, and the fabricated antibody layer was applied for the detection of BSA. The extent of BSA–antibody binding was measured using SPR and its lower detection limit of BSA was 100 pM.