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Bioterror Detection Draws Closer

WHILE RADIATION sensors and chemical gas “sniffers” dot the country’s urban landscape, effective, rapid detection of contamination or infection by biological agents is not yet possible.

Quickly detecting dangerous contamination at the site of a biological attack is an issue of quantity, explains Professor B.R. Singh of the University of Massachusetts-Dartmouth. Just a single microgram (1/1,000,000 of a gram) of botulinum can kill, meaning that terrorists don’t need a lot to achieve their objectives. By contrast, a fatal dose of cyanide for a 150-pound person may require 70 milligrams.

The work of Singh, and colleagues at Sandia National Laboratories and the Hercules, California-based Bio-Rad Laboratories, won’t help to detect the pathogens in the environment, but they will allow diagnosis of human biotoxin infection within 15 minutes, rather than the hours or days currently required.

The technology’s key element is miniaturization. The chemical reactions that drive the test occur more quickly in a dramatically confined space than they would in a larger environment, like a test tube or vial, explains Sandia researcher Anup Singh (no relation).

He describes the device as “a lab on a chip,” or more accurately, a lab on a glass or plastic slide. The slides resemble those from a high school biology class crossed with a microprocessor chip, containing a network of minute internal channels, 40 microns deep by 200 microns wide (0.04 mm by 0.2 mm).

For a test, a slide is installed into the system’s diagnostic device along with a sample of the test subject’s blood, which the machine pumps into the slide’s channels. The machine then pumps in antibodies for a given pathogen; the antibodies have been treated with fluorescent dye.

If the pathogen is present in the blood, the antibodies will bond to them. Different antibodies can be dyed different colors and injected into separate channels on the same slide, offering simultaneous tests for different toxins.

Next, the slide is subjected to a mild electrical field. The magnetic effect induces motion in the molecules, with lone antibodies moving in the opposite direction from those bound to pathogens. Sensors in the diagnostic device detect the opposing flows, if present, and their volumes, determining both the presence of the pathogen and the volume of infection.

The device required to conduct the procedure would not be handheld, but it would be mobile—smaller than a desk, researchers say.

The five-year, $3.2 million research program, funded by the National Institutes of Health, is developing “assays” for botulism, staph infection, E. coli, and C. perfringens. With refinement, the technology holds the promise of detecting potential terrorist pathogens, including anthrax and smallpox, and it will likely function using a simple saliva sample rather than blood, researchers say.