Magnetic field-assisted SPR biosensor based on carboxyl-functionalized graphene oxide sensing film and Fe3O4-hollow gold nanohybrids probe.

A novel surface plasmon resonance (SPR) biosensor, coupled with the magnetic bioseparation technique, was constructed and used to the determination of human IgG. Carboxyl-functionalized graphene oxide (cGO) sheet was employed as the sensing film for the efficient immobilization of capture antibody (Ab1). Nanoconjugates (FHAb2), obtained by binding detection antibody (Ab2) to the nanohybrids containing Fe3O4 nanoparticles (Fe3O4 NPs) and hollow gold sphere nanoparticles (HGNPs), were used to specifically collect the target analytes from sample solutions and serve as labels. Owing to the notable plasmonic fields spreading over inner and outer surfaces, HGNPs played key roles in amplifying the SPR response signals originating from the dielectric changes on the sensing films during the binding of Ab1 and human IgG-Ab2FH complexes. In addition, FHAb2 were also used as "vehicles" for the rapid delivery of the separated and enriched target analytes from sample solutions to the sensor surface via an external magnet. In the present method, taking advantages of the magnetic field-driven mass transfer and the significant signal amplification effect of FHAb2, the separation and analysis of human IgG in serum samples are quite effective and sensitive. The limit of detection was 1.88ngmL(-1), which is about 260-fold lower than that obtained by routine SPR biosensors with sandwich assay.
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