The BARC biosensor applied to the detection of biological warfare agents

The Bead ARray Counter (BARC) is a multi-analyte biosensor that uses DNA hy bridization, magnetic microbeads, and giant magnetoresistive (GMR) sensors to detect and identify biological warfare agents. The current prototype is a table-top instrument consisting of a microfabricated chip (solid substrat e) with an array of GMR sensors, a chip carrier board with electronics for lock-in detection, a fluidics cell and cartridge, and an electromagnet. DNA probes are patterned onto the solid substrate chip directly above the GMR sensors, and sample analyte containing complementary DNA hybridizes with th e probes on the surface. Labeled, micron-sized magnetic beads are then inje cted that specifically bind to the sample DNA. A magnetic field is applied, removing any beads that are not specifically bound to the surface. The bea ds remaining on the surface are detected by the GMR sensors, and the intens ity and location of the signal indicate the concentration and identity of p athogens present in the sample. The current BARC chip contains a 64-element sensor array, however, with recent advances in magnetoresistive technology , chips with millions of these GMR sensors will soon be commercially availa ble, allowing simultaneous detection of thousands of analytes. Because each GMR sensor is capable of detecting a single magnetic bead, in theory, the BARC biosensor should be able to detect the presence of a single analyte mo lecule. (C) 2000 Elsevier Science S.A. All rights reserved.