Rapid DNA testing

University of Rochester Chemistry Department researchers have developed a method for rapidly testing DNA. The method can be used to help forensics labs identify criminals, test ponds and pools before children swim in them, and identify harmful genetic sequences in medical research, to name only a few applications. The procedure quickly and inexpensively identifies genetic sequences in any sample of DNA.

The technology is a novel fluorescent DNA screening assay, which rapidly determines whether specific DNA target sequences are present in an analyte. In simple terms, the analyte contains the DNA target sequences as well as other DNA sequences, and the assay filters out only the targets. The assay is based on the electrostatic properties of DNA.

The principle underlying the method is that single-stranded DNA and double-stranded DNA have significantly different affinities for attaching to ionically charged gold nanoparticles. Single-stranded DNA adsorbs on negatively-charged citrate ions on the gold nanoparticles while double-stranded DNA does not.

The assay determines whether a fluorescently-tagged short probe sequence of single-stranded DNA matches a sequence in the target analyte. When it does not, the fluorescently tagged probe adsorbs on a gold nanoparticle and its fluorescence is quenched. If the probe sequence is able to hybridise to the target, it will not adsorb on the gold and its fluorescence persists.

The method is simple and effective. It costs very little, and it''s very quick.

Using gel electrophoresis, each test takes 1 hour and can cost as much as $1.00. Setting up a lab for gel electrophoresis requires a capital expenditure of $5000. By contrast, the University of Rochester's technique only requires 5 minutes, and it costs approximately $0.05 per test and the capital expenditure to set up a lab with the technique is only $600.

Perhaps more important than the savings in time and money, the new method works to determine single-base mutations in DNA, whereas gels cannot do this without even further processing.