We've written about "DNA Barcoding" before, but as a means of identifying species via short strands of unique DNA. But it turns out that there's a different kind of DNA Barcoding out there, one that uses non-expressing DNA strands as tags for monitoring pathogens. A group of researchers at Cornell have just come up with a way to make these tags easier to create, less expensive, and more useful.
The researchers use "dendrimer-like DNA," short Y-shaped strands of DNA. The DNA employed doesn't actually code for anything; instead, it's used as a physical structure for the tags.
An antibody or some other molecule that will bind to the molecule to be detected is attached to one of the loose ends of the DNA. To other ends are attached molecules of fluorescent dye in a predetermined pattern.
For example, one probe might contain four molecules of green dye and one of red. Another might have three molecules of green and two of red, and so on. If a mixture of several probes is added to a solution containing, for example, E. coli bacterial DNA, only probes with a particular color code will be programmed to bind to that DNA. The results can be seen under a fluorescent light microscope using colored filters that pass only one color at a time. [...] The researchers point out that the nanobarcode detection system does not require complex preparation of a sample and can be applied to living cells. The technology could be used in genomic research, clinical diagnosis, drug testing, environmental monitoring and monitoring for biological terrorism, they suggest.
(Additional information on the construction of dendrimer-like DNA can be found here.)
What makes this technique notable -- aside from its relative simplicity and utility in environmental sensors -- is that it uses DNA not for its genetic characteristics, but as a nanoengineering building block. Much is known about synthesizing DNA and controlling its assembly, and as a result, DNA can be very useful as a nanoconstruction component. We've reported in the past about other examples of DNA-based nanoassembly.
Just a friendly reminder that nanotechnology doesn't always mean tiny robots or carbon buckytubes.