Studies of Fe3O4/Ag/Au composites for immunoassay based on surface plasmon resonance biosensor

A novel method immunosensor based on chemically functionalized Fe3O4/Ag/Au nanocomposite was developed. Fe3O4/Ag seeds were coated with Au and Fe3O4/Ag/Au nanocomposites were obtained. The nanocomposites could be obtained without violent stirring and the operation was easy and convenient. The magnetic nanocomposites can be easily immobilized on Au film of the surface plasmon resonance (SPR) biosensor with a magnetic pillar. The immobilization of Fe3O4/Ag/Au nanocomposites on the Au film leads to a large shift in resonance wavelength, which is due to the increase of the sensing membrane thickness, high dielectric constant of Ag and Au particles, and electromagnetic coupling between Fe3O4/Ag/Au nanocomposites and the Au film. The effects of Fe3O4/Ag/Au nanocomposites on the sensitivity of SPR biosensor were also investigated. As a result, the biosensor based on Au film shows a response for dog IgG in the concentration range of 1.25–20.00 μg ml−1, whereas the SPR biosensor based on Fe3O4/Ag/Au nanocomposites shows a response for dog IgG in the concentration range of 0.15–40.00 μg ml−1. The sensitivity of the SPR biosensor based on Fe3O4/Ag/Au nanocomposites is higher than that based on Au film.

A schematic diagram of the immobilization of antibody on the surface of the Au film. () Fe3O4/Ag/Au nanocomposites, () Fe3O4 nanoparticles () antibody, () antigen.Figure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideHighlights
► Fe3O4/Ag/Au composites were synthesized.
► Two types of SPR biosensors were prepared.
► The magnetic composites can be easily immobilized on the surface of SPR biosensor.
► The magnetic composites could enhance the sensitivity of the SPR biosensor.