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Virus counter. This probe contains a quartz crystal to measure virus concentrations over seven orders of magnitude.

Listening for Viruses

Scientists have developed a new, sensitive way to detect viruses. The technique uses a tiny microphone that attracts viruses, then starts vibrating and "listens" for the sound the viruses make as they let go.

Traditional techniques for detecting the presence of viruses all have limitations. Some amplify the virus's genetic material with the polymerase chain reaction, which is error-prone; others rely on detecting antibodies against the virus, but often do not work in the early stages of infection. A recent alternative approach is a vibrating quartz crystal coated with antibodies that bind a specific virus. The more virus particles attach to the crystal, the more its vibrations slow down, offering an indication of the virus concentration in the sample. But these devices are not very sensitive to small numbers of viruses.

So chemist David Klenerman and his colleagues at the University of Cambridge, United Kingdom, turned things around. They first let particles of herpes simplex virus (HSV) attach to the crystal's antibodies, and then vibrate the quarter-sized crystal ever harder. All at once, the virus particles are thrown off. That shudders the crystal, which acts like a microphone and converts the vibration into an electrical signal. The size of the electrical peaks corresponds to virus concentration, the team reports in the September issue of Nature Biotechnology, as long as that concentration was between 1 virus particle and 10 million virus particles per microliter. The system only detected HSV and wasn't thrown off by the presence of other viruses.

The researchers have formed a company, Akubio Ltd., and are now working on miniaturizing the instruments, which they hope to reduce to the size of a cellular phone, and on equipping them with antibodies specialized to detect other viruses. The technology looks solid, says Scripps biophysicist Erica Ollmann Saphire. The instrument is "very promising" because it is sensitive, specific, and fast, she says.

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