SENSITIVE DETECTION OF BIOTOXOIDS AND BACTERIAL-SPORES USING AN IMMUNOMAGNETIC ELECTROCHEMILUMINESCENCE SENSOR

Extremely sensitive detection of various biotoxoids and bacterial spores using the commercial ORIGEN(R) analyzer was achieved by capture on antibody-conjugated micron sized magnetic beads (MBs) followed by binding of ruthenium (II) trisbipyridal chelate (Ru(bpy)(3)(2+))-labelled reporter antibodies. Immunomagnetically captured target materials were collected on a magnet. Electrochemiluminescence (ECL) was evoked from the Ru(bpy)(3)(2+)-tagged reporter antibodies by application of an electrical potential. Femtogram sensitivity levels were obtained for all biotoxoids tested including botulinus A, cholera beta subunit. ricin and staphylococcal enterotoxoid B by this immunomagnetic (IM)-ECL approach. An IM-ECL assay for Bacillus anthracis spores yielded a detection limit of at least 100 spores. The ECL signal was a function of analyte quantity over several orders of magnitude, but the immunological 'hook' effect at high antigen loads made quantitation impossible over a broader range. All assays were performed with a maximum combined incubation and assay time of approximately 40 min. This work demonstrates the extreme sensitivity of the IM-ECL approach for soluble and particulate antigens.