Researchers at the University of Georgia, US, have developed a technique for rapidly identifying minute traces of viral genetic material, using just light. The method pioneered by Ralph Tripp and his colleagues makes use of a phenomenon called Raman Spectroscopy. When light hits a surface it scatters, producing a pattern, or Raman spectrum, which is unique to that surface, rather like a fingerprint. The same trick works with genetic material, either DNA or RNA, and so it's possible to tell different viruses apart on the basis of how their genetic material alters the frequency of the scattered light. This was previously well known, but the method couldn't be used in virus detection because the signal it produced was too weak. Now the team have found that by adding tiny silver nanorods to the surface and illuminating them with near-infrared laser light they can make the signal 100 million times stronger, making the system so sensitive that it can detect a single virus particle. It's also extremely quick, requiring only 60 seconds to complete an identification, which means it could easily be used to develop a handheld sensor. "You could apply it to a person walking off a plane to know if they're infected," points out Tripp. The researchers are currently working on an "encyclopaedia" of known viral Raman-shift "fingerprints", so that technicians will know immediately if they are dealing with an unknown virus.
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