Sensors Mag

Nanowire Sensor for Bioweapon Detection

October 3, 2006 By: Peter Adrian

This content is excerpted from Sensor Technology Alert and Newsletter, a sensor intelligence service published by the Technical Insights unit of Frost & Sullivan.

Sensor Technology Alert

The detection of radiological, biological, chemical warfare agents, and other hazardous vapors has great significance in enhancing homeland security efforts. Various kinds of biosensors are now available in the market. However, the shift is toward developing smaller portable systems with highly sensitive sensors. With the advent of nanotechnology, gold nanomaterials are currently being experimentally developed and evaluated for use in sensors for bioweapon and toxin detection.

A research team at the Lawrence Livermore National Laboratory in Livermore, California, has developed a barcoded or multistriped nanowire as a platform to rapidly detect biowarfare agents. This promising new development can be used in the early detection of very small amounts of bioweapons or microorganisms. The team, led by Jeffrey Tok, used a sensing method based on sandwich immunoassays, which is comparable to the sensing method used in typical home pregnancy test kits, where the target molecule that is to be detected gets sandwiched and bound between two antibodies. In design, one antibody is bound to a substrate and the other antibody, carrying a visible dye, is mobile. In the presence of the target molecule, a blue dot is created when the two sides of the sandwich recombine at the spot where the immobile antibody is bound.

With the suggestion that nanowires barcoded with different striped patterns can be loaded with a series of antibodies that could possibly latch on to different targets, the team of researchers, along with the University of California at Davis, Stanford University, and Nanoplex Technologies, has developed a prototype model by experimentally replacing the blue dye of the pregnancy test with a fluorescent dye, and replacing the solid substrate with a mobile nanowire with alternating stripes of silver and gold.

The prototype demonstration of the wire construct sensed harmless representative bioweapons, such as viruses, bacterial spores, and proteins, at a detection limit comparable to that of microarrays. The team further showed that, with an addition of a nickel cap at each end of the barcoded nanowire, they can be made magnetic, facilitating easy separation of nanowires from solution for analysis, without loss of sensor performance, allowing an assay completion in three to four hours.

"The focus is now on developing this approach into a portable and automatic, microfluidic device that can potentially detect several bioweapons at the same time," Tok told Sensor Technology.

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