Researchers at the University of Pittsburgh and at Nanomix in California have discovered a new way of detecting specific DNA sequences, at the resolution of a single base.
The device is simple and elegant. An ordered sequence of electrodes is overlayed with a random mesh of carbon nanotubes, as in the following image:
The visible maze-like sequence in the left image is the electrodes. In the right image, you can see a random mesh of tiny carbon nanotubes. Electric current can flow through the circuit by using the carbon nanotube mesh as a bridge.
The carbon nanotubes are then bathed in a solution containing a DNA sequence that is complementary to the one to detect. So for example, if you were looking for the sequence AACCGGTT, you would create the sequence TTGGCCAA, multiply it a few million times, and coat the carbon nanotube mesh with it. (As a reminder, in DNA, the bases A and T, and C and G, respectively, always pair up together.)
Next, you place a drop of subject blood on the circuit. If the matching DNA sequence is present, it will bond to the complementary sequences, which are connected to the carbon nanotube mesh. Current passing through the device drops dramatically, indicating a match.
One real-world application for this would be for an instantaneous, highly accurate field-test for specific viruses. For example, currently, officials are testing birds all over the world for bird flu. This technology could provide real-time test results, dramatically improving our ability to recognize and contain the virus. The technology should be cheap to manufacture because the nanotubes do not need to be ordered. The electrodes are spaced at the micrometer scale, which means they can easily be created using conventional manufacturing techniques.