This paper describes an ultrasensitive surface plasmon resonance (SPR) detection method using biofunctionalized gold nanorods for the direct detection of protein biomarkers. Immunoglobulin E (IgE), which has separate antibody and DNA aptamer binding sites, was chosen as a model protein for which a sandwich assay platform was designed. Detection was achieved via the specific adsorption of unlabelled IgE proteins onto the surface immobilized aptamer followed by the specific adsorption of anti-IgE coated gold nanorods (Au-NRs). Using the biofunctionalized nanorods in conjunction with SPR, we were able to directly measure IgE proteins at attomolar concentrations. This is a remarkable 108 enhancement compared to conventional SPR measurements of the same surface sandwich assay format ‘anti-IgE/IgE/surface bound IgE-aptamer’ in the absence of gold nanorod signal amplification.
- attomolar detection
- protein biomarkers
- biofunctionalized gold nanorods
- surface plasmon resonance