Sub-attomole oligonucleotide and p53 cDNA determinations via a high-resolution surface plasmon resonance combined with oligonucleotide-capped gold nanoparticle signal amplification

Oligonucleotide (ODN)-capped gold nanoparticles (Au–NPs) were used in a sandwich assay of ODN or polynucleotide by a flow injection surface plasmon resonance (SPR). A carboxylated dextran film was immobilized onto the SPR sensor surface to eliminate nonspecific adsorption of ODN-capped Au–NPs. The tandem use of signal amplification via the adlayer of the ODN-capped Au–NPs and the differential signal detection by the bicell detector on the SPR resulted in a remarkable DNA detection level. A 39-mer target at a quantity as low as 2.1 × 10−20 mol, corresponding to 1.38 fM in a 15 μl solution, can be measured. To our knowledge, both the concentration and quantity detection levels are the lowest among all the gene analyses conducted with SPR to this point. The method is shown to be reproducible (relative standard deviation values <16%) and to possess high sequence specificity. It is also demonstrated to be viable for sequence-specific p53 cDNA analysis. The successful elimination of nonspecific adsorption of, and the signal amplification by, ODN-capped Au–NPs renders the SPR attractive for cases where the DNA concentration is extremely low and the sample availability is severely limited.