In this report, gold nanorods (GNRs) were used to enhance the sensitivity of the wavelength-modulated surface plasmon resonance (SPR) biosensor. The GNRs were designed and fabricated through seed- medicated growth and surface activation by a layer of a weak polyelectrolyte, poly(acrylic acid) for the attaching antibody. Rabbit anti-goat IgG was immobilized on GNRs, and sandwich assays were carried out to detect goat IgG using a wavelength-modulated SPR biosensor. The detection sensitivity of the nanorod-conjugated antibody is 25–100 times more sensitive than the SPR biosensor without GNRs. Drastic sensitivity enhancement, owing to the electromagnetic interaction between the nanotag and the sensing film, was maximized using the longitudinal plasmonic resonance of the GNRs. GNRs could significantly enhance the sensitivity of the SPR biosensor, and the maximum enhancement effect can be achieved when the longitudinal SPR peak wavelength of GNRs functionally matches the surface plasmon wavelength.
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