Hears to Your Health

A sensor lets researchers listen for germs

When University of Cambridge scientists first heard a virus wresting itself from the tenacious clutch of an antibody, the sound should have elicited a collective sigh of relief from fretting patients everywhere. The researchers were testing a new device that can hear the presence of a virus in a blood sample. For many patients, who sometimes wait days to get test results, the invention could mean on-the-spot detection of HIV, hepatitis and dozens of other pathogens, including anthrax and smallpox.

The Cambridge experiment involved a tiny slice of quartz crystal layered with antibodies. A virus in the first case, herpes simplex was introduced and subsequently bound to an antibody on the crystal. The scientists then slowly increased the frequency of an electric current flowing into the quartz. As the quartz oscillated, it whipped the virus and antibody back and forth.

Eventually the herpesvirus tore away from the antibody, emitting a faint pop. "If you apply enough force to a stick, it will snap and you hear a sound," explains Matthew Cooper, one of six researchers involved in the project. "Likewise, we can hear the sound of the bonds snapping when we break apart a virus and an antibody." The quartz acts like a piezoelectric microphone, converting mechanical vibrations into electrical impulses. Similarly, when a virus breaks from an antibody, the quartz changes the vibrations into detectable electrical signals.

The entire process, termed rupture event scanning, is far better than current enzyme- or biochemical-based viral tests, which reveal the existence of antibodies but can't determine whether or not a subject is carrying the associated virus. "We are directly detecting the virus," Cooper points out, "which gives you a much more accurate prognosis."

Using targeted antibodies, the quartz microphone could be fashioned to recognize the sounds of a multitude of viruses. "It could even detect bioterrorist germs," Cooper says: add a microthin film of anthrax or smallpox antibodies to the crystal, then douse it with a sample of infected blood for an instant diagnosis. He is quick to add that the technology is at least three years from its commercial debut. To that end, the Cambridge team has formed a company called Akubio. With $1.7 million in funding (mostly from venture capitalists), Cooper wants to engineer a cell phone-size tool that can eavesdrop on "cells, bacteria and a variety of different substances in the body."