Authors: M. Nakahara, S. Taniguchi and T. Inoue
Affilation: Hitachi, Ltd., Japan
Pages: 435 - 438
Keywords: gold nanoparticles, fluorescence enhancement, fluorescence quenching, DNA detection, DNA microarray, molecular beacon
We developed a novel DNA detection system using a single stranded probe oligonucleotide with a fluorophore immobilized on two-dimensionally assembled gold nanoparticles. This system enables the detection of amplified DNAs without fluorescence labeling. In the absence of a target DNA, fluorescence from cyanine dyes labeled at the distal end of the probe is quenched via energy transfer to the nanoparticles on which the dye moiety is adsorbed. However, after a non-labeled complementary target DNA is hybridized with the probe, rigidity of the double stranded DNAs allows the dyes to desorb from the particles. Consequently, the fluorophore is liberated from the quenching region, and fluorescence is enhanced by the strong local electromagnetic field in the vicinity of the gold nanoparticles. This relative increase in fluorescence intensity after hybridization was evaluated on assembled gold nanoparticles 5 to 50 nm in diameter. The relative increase was maximized on gold nanoparticles of 10 nm where both quenching and enhancement factors were optimal. The correlation between the relative increase and concentration of the target DNA reveals that the system selectively detects non-labeled DNAs quantitatively with high sensitivity.