DNA sequence detection using selective fluorescence quenching of tagged oligonucleotide probes by gold nanoparticles.

Simple, fast, economical, and sensitive detection of specific DNA sequences is crucial to pathogen detection and biomedical research. We have designed a novel fluorescent assay for DNA hybridization based on the electrostatic properties of DNA. We exploit the ability to create conditions where single-stranded DNA adsorbs on negatively charged gold nanoparticles while double-stranded DNA does not. Dye-tagged probe sequences have their fluorescence efficiently quenched when they are mixed with gold nanoparticles unless they hybridize with components of the analyte. Subfemtomole amounts of untagged target are detected in minutes using commercially available materials. Target sequences in complex mixtures of DNA and single-base mismatches in DNA sequences are easily detected.