Wanted: A Bioterror Sensor

Auburn, April 9, 2003 --- Imagine a sensor that could be posted at subways or even carried along by soldiers to detect the presence of potentially deadly chemical or biological agents.

Following the September 11 tragedy, the federal government doubled financing for counterterrorism research, and bioterror sensors were at the top of the list of priorities, The New York Times recently reported.

(One example, above, of a bioterror sensor: A network constructed from mouse embryo cells and attached to electrodes may help water systems and other facilities monitor for bioterrorist attacks.  Photo courtesy of the University of Texas Center for Network Neuroscience.)

In bioterrorism terms, it’s the equivalent of building the perfect mousetrap.  But try as they might, experts have not yet come close to developing such a sensor.  And that’s likely to be the case for the foreseeable future.

“There’s no such thing as an ideal sensor – not yet, at least,” says Dr. Jean Weese, an Alabama Cooperative Extension System food scientist and Auburn University associate professor of nutrition and food science.  “We’re still a long way from having a machine or a chip that tells us what we need to know -- let alone, that senses dangerous gasses or biological substances and sends off an alarm.”

That hasn’t prevented some researchers from trying, though many, including Weese, are running up against the same problem – the irritating tendency of many of these devices to overdo their job, detecting danger where it doesn’t exist.  

One added problem is that it is still scientifically impossible to construct a one-size-fits-all detector capable of detecting a variety of different threats. So, for now, at least, a sensor’s makeup all depends on the type of substance it’s supposed to detect.

For example, shining an ultraviolet laser in the air will cause an approach cloud of biological molecules to glow faintly, thereby providing troops with a few minutes warning to soldiers on the battlefield. But it won’t detect an approaching cloud of toxic chemicals.

Most detectors designed for chemical attacks use one of two methods: (1) a surface wave acoustics system that vibrates when certain chemicals attach to them and (2) ion mobility spectroscopy that electrically charges nerve-gas chemical molecules so that they can then be measured and identified.            

Neither of these approaches is foolproof.  Surface detectors can be triggered by other chemicals attaching to its membrane, while ion mobility detectors can be fooled by molecules comparable in size to nerve gas molecules.

Weese’s own experience with biodetectors involves work with other Auburn University researchers on a biochip designed to detect potentially deadly pathogens, such as E.coli O157:H7, in meat products. 

“What this involves, basically, is a marriage of microchips and biology,” Weese says. “Each of these microchips would be equipped with antibodies, so that when pathogens come in contact with them, the chip would be keyed.”

Ultimately, Weese and the other researchers hope to develop a chip that could be inserted into grocery store meats and that, if pathogens were present, would emit a warning signal during scanning at the check-out line.

Weese and the other researchers have explored three different approaches.           

“Part of it can be done by measuring weight,” she says.  “When the antibody comes in contact with the pathogen, its weight increases, and this, in turn, keys the sensor.”

“There are other ways to do it too, using electromagnetic and chemical methods.”

Despite their success, the researchers have run up against the same limitations that have plagued similar approaches – the inability to develop a one-size-fits-all sensor.

“For it to work adequately, the sensor is going to have to be specific to what we tell it to be,” she says, “whether it’s Salmonella, E.coli or whatever.”

“True, we could even develop a chip to detect more than one organism, but accounting for all of them would be tough.”

“And even if we could account for all the stuff that can hurt us, there’s always the likelihood that something else will come around, which means we’ll have to start all over again.”

(Source: Dr. Jean Weese, Alabama Cooperative Extension System Food Scientist and Auburn University Associate Professor of Food Science and Nutrition, 334-844-3269)

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