Single-stranded DNA, on the other hand, provided repeatable responses to odors, and this response depended on the specific sequence of four nucleotide types that make up the genetic code. With a typical sequence about 20 nucleotides long, the team has the potential to create millions of sensor types. In the current issue of PLoS Biology, the researchers describe the response of just 30 sequences, but White says that now they have identified hundreds of useful DNA sequences, including one that responds to the vapor signature of TNT-containing land mines–an unusual finding indicating the versatility of the technique.
Alan Gelperin at Philadelphia’s Monell Chemical Senses Center hails the discovery as a major step. “The whole field has been hindered by a lack of diverse sensor technology,” he says. “This is the first demonstration that [DNA] could be used in this way.” Since first learning of the approach during a conference, Gelperin has collaborated with University of Pennsylvania physicist Charlie Johnson to take the concept one step further by incorporating an electronic readout made with carbon nanotube transistors.
For now, White says that his team has incorporated his DNA sensors alongside the synthetic polymers in targeted projects, including one device for detecting ammonia gas, which would be useful for warning emergency responders at toxic spills or for monitoring pollution from livestock operations. He says that there is even interest among vintners in developing a device that could help sniff out counterfeit wines. “This was news to me,” White says, laughing.