Site-directed antibody immobilization on gold substrate for surface plasmon resonance sensors

A simple method for the site-directed immobilization of antibodies on gold substrates has been developed for surface plasmon resonance (SPR) applications. A freshly prepared gold surface on a glass slide was modified with Protein A via homobifunctional cross linker dithiobissuccinimide propionate (DSP) to achieve uniform, stable, and sterically accessible antibody coating. The density of the immobilized antibodies bound to Protein A was examined as a function of the protein concentration, buffer pH, buffer type and reaction time. The suggested scheme was also employed for the modification of gold-coated substrates for quartz crystal microbalance (QCM) applications. The modified gold surface was stable for several weeks and the reproducibility was satisfactory. The current fabrication technique could be applied to construct other immunosensors or biochips.