Design and performances of immunoassay based on SPR biosensor with Au/Ag alloy nanocomposites

A novel method for detecting human IgG is reported, which is based on Au/Ag alloy nanocomposites for amplifying surface plasmon resonance response. Au/Ag alloy nanocomposites were characterized in detail by transmission electron microscopy (TEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). Covalent immobilization of about 24 nm diameter of Au/Ag alloy nanocomposites on the Au film results in a large shift in resonance wavelength, which is due to the increase of the thickness of the sensing membrane, high dielectric constant of Au/Ag nanoparticles, and electromagnetic coupling between Au/Ag alloy nanocomposites and Au film. The SPR biosensor based on Au/Ag alloy nanocomposites exhibits a satisfactory response for human IgG in the concentration range of 0.15-40.00 μg mL⁻¹. While the biosensor based on Au nanoparticles shows a response in the concentration range of 0.30-20.00 μg mL⁻¹ and the biosensor based on Au film shows a response for human IgG in the concentration range of 1.25-20.00 μg mL⁻¹.