Biosensor system helps detect pathogens cleanly, rapidly



WASHINGTON, D.C. — Biosensor technology developed at the U.S. Naval Research Laboratory (NRL; is being incorporated in a contamination-controlled laptop veterinary diagnostic system now under development by Seahawk Biosystems Corp. (Austin, Texas.;

The system is based on the NRL's Bead ARray Counter (BARC) magnetic microarray technology, and will be combined with proprietary assay protocols in hopes of greatly reducing the incidents of false positives and false negatives when testing for pathogens in pets. Seahawk says its tabletop system, scheduled to be available in 2006, will let veterinarians perform a panel of health tests simultaneously and more specifically than with current methods. The company claims that costly and time-consuming steps required to amplify or enrich the samples will be significantly reduced if not eliminated.

According to NRL, its BARC biosensor uses DNA microarrays, magnetic microbeads, and giant mangetoresistive (GMR) magnetic field sensors to detect and identify biological molecules. At the core of the sensor is a small, microfabricated chip with a flow cell for sample testing and containing a GMR sensor array that detects up to eight different pathogens.

A biosensor-based diagnostic system, based on the U.S. Naval Research Laboratory's Bead ARray Counter (BARC) magnetic microarray technology, will be combined with proprietary assay protocols from Seahawk Technology to greatly reduce the incidence of false positives and false negatives when testing for pathogens at veterinary clinics.
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"Our patented assays use magnetic labels, which are detected by microsensors integrated under the capture surface," explains Lloyd Whitman, head of the NRL's Surface Nanoscience and Sensor Technology Section. "These labels can be detected with high sensitivity."

The 5-mm wide BARC chip is mounted in a chip carrier board housed within a microfluidics-driven assay cartridge. Specific hybridization is measured and discriminated from non-specific background through magnetic microbeads that bind to the captured target DNA. The GMR sensors then detect the beads tethered to the surface, with intensity and location of the signal indicating the concentration and identity of specific pathogens.

"Our assays also incorporate a patent-pending step we call 'fluidic force discrimination' that greatly reduces the label background noise associated with non-specific binding," Whitman says. "The combined result is a test system with very high analytical sensitivity and a very low background signal."

The NRL says that a complete assay can be performed with its technology in about 30 minutes.