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Nanowire bar codes enable detection of biowarfare agents

Sep 2006
A team of researchers from California has introduced metallic-striped nanowires to aid in detecting biological warfare agents with optical reflectance and fluorescence imaging.

As described in the group’s Angewandte Chemie manuscript published online Aug. 4, the nanowires were structured with submicron gold, silver and nickel layers and coated with antibodies that bound to fluorophore-tagged antigens in a solution. In both single and multiplex immunoassays, the team used three nonpathogenic antigens to represent a variety of biological warfare agents, from micron-size bacterial spores to nanoscale protein toxins. Each nanowire had a unique “bar-code-like” pattern that corresponded to its particular antibody coating.

Gold- and silver-striped nanowires are coated with antibodies and suspended in a solution. Fluorescence imaging can reveal which fluorophore-tagged antigens, representing biological warfare agents, are present in the solution.

Reflectance/fluorescence image pairs were taken with a Zeiss inverted microscope fitted with bright-field reflectance and fluorescence filter sets. The reflectance images allowed the researchers to identify the stripe patterns of each nanowire and to determine which antibodies coated them. Depending on which nanowires were fluorescently lighted, they could determine which antigens were present in the solution. The fluorescent intensity represented the concentration of each antigen.

The researchers, from Lawrence Livermore National Laboratory, Stanford University, Nanoplex Technologies Inc. of Mountain View and the University of California, Davis, hope to incorporate the assay onto a microfluidic device to enable a rapid, portable and affordable multiplex biosensing system. Because the assay can be completed in a matter of hours, it will allow quick and accurate detection of infectious biological agents.

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