Nanowires built to fight bioterrorism

Nanowire "bar code" system designed for use in portable, quick-acting sensors that can detect pathogens.

Scientists have discovered a new method for detecting deadly pathogens like Anthrax or smallpox almost immediately after they've been released into the air.

Researchers at Lawrence Livermore National Laboratory said this week that they've developed a so-called nanowire bar-code system that could one day be used to create portable, quick-acting sensors designed to identify hundreds of airborne pathogens within minutes.

"If there is an outbreak, we want to know in a fast, efficient manner what agent has infiltrated the room," said Jeffrey Tok, a scientist in LLNL's biosecurity and nanosciences lab and the lead researcher on the development. "This technology we've developed signifies an initial, giant step toward accomplishing that."

The scientists created pathogen-detecting nanowires by electrochemically depositing metals into tiny cavities of porous mineral solids. They then layered gold and silver in striping patterns analogous to those used in grocery store bar codes.

Each striping pattern is assigned to a specific antibody, or protein, that binds to the nanowire and also will bind to a target pathogen, such as Anthrax spores. If a pathogen is present in the air, it will bind to the antibody that is attached to the nanowire and also will bind to other, specific antibodies that have been fluorescently tagged. The presence of fluorescing antibodies on the nanowires thus indicates when a specific pathogen is present.

"Imagine 100 nanowires, each with a specific pattern and antibody," Tok said. "You look for nanowires that are fluorescing and automatically you know which pathogens are present."

Concerns about biowarfare increased dramatically in the wake of the terrorist attacks of 9/11, but the threat has been around for years. In the 1990s, a cult released sarin nerve gas in Tokyo's subway system, killing nearly a dozen people and causing thousands more to be sick. And in the months following 9/11, anthrax spores were found in letters mailed to U.S. congressional members and media outlets.

U.S. security services currently use a system called the Autonomous Pathogen Detection System, or APDS, to analyze air quality and detect pathogens in places like New York subway stations.

The APDS relies on so-called micro-beads, which are injected with different ratios of dyes that mirror and bind with pathogens. As the system sucks in air from the atmosphere, the beads flow, one at a time, through a channel. A florescent beam analyzes any pathogens collected in the beads as they flow through the channel. Data about the findings is then transmitted wirelessly to a centrally monitored area.

But the APDS is about the size of a metal newspaper dispenser, which limits its portability, Tok said. With a magnetic nanowire platform, he said, the lab could build next-generation devices that are portable and yet can deliver fast, accurate and easily decipherable results about air quality.

The barcode structure also allows scientists to test the air for multiple pathogens at once, Tok said, while the APDS is designed to sense for pathogens one at a time.

Tok said that the lab is currently working on a prototype of a nanowire device and hopes have one operational in the next few months for testing.

The LLNL, whose mission is ensuring national security, is funded by the U.S. Department of Energy and the National Institutes of Health. Researchers from Stanford University also played a part in developing the nanowire system. And the nanowire technology was built specifically by technology company Oxonica and given to LLNL for the project.

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