A highly sensitive SPR biosensor based on a graphene oxide sheet modified with gold bipyramids, and its application to an immunoassay for rabbit IgG

A new SPR sensing substrate was fabricated that is based on the use of graphene oxide (GO) and gold bipyramids (GBPs). It can substantially improve the sensitivity of wavelength modulation SPR biosensors. First, a support consisting of a sheet of single layered GO was prepared, and its morphology and thickness were determined by atomic force microscopy (AFM). GBPs were synthesized and modified with staphylococcal protein A (SPA) for the oriented immobilization of antibody. GBPs modified with SPA were assembled on GO sheets through covalent attachment. The resulting SPR biosensor exhibits a highly sensitive response to rabbit IgG in the 0.15-40 mu g mL(-1) concentration range. The limit of quantification is better by factors of 4 and 16 compared to those obtained with gold nanoparticle-based, and conventional gold film-based sensors, respectively. In our expectation, this GBP-based SPR biosensor has a wide scope in that it may be employed to develop detection schemes for many other biomolecules by changing the corresponding receptor on its surface.