Rapid detection of Mycobacterium tuberculosis cells by using microtip-based immunoassay
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This paper describes a microtip-based approach of concentrating target analytes for a highly sensitive bioassay. As an example, rapid screening of bacterial whole cells is presented to detect Mycobacterium tuberculosis (MTB), a pathogenic bacterium for human tuberculosis (TB). The concentration and detection is performed with three sequential steps of (1) attracting bacterial whole cells in the vicinity of a microtip by alternating current electroosmotic flow; (2) capturing the cells onto the microtip by capillary action; (3) binding fluorophore-labeled polyclonal antibodies to the cells followed by fluorescence measurement (immunofluorescence). Through this mechanism, MTB cells have been detected to the concentration of 8,000 cells/mL within 10 min. This sensitivity is comparable to that of Ziehl–Neelsen smear microscopy, a common culture-free screening method for diagnosis of TB. For comparison, Escherichia coli O157:H7 cells have also been detected to the concentration of 30,000 cells/mL in the same way.
KeywordsImmunoassay Immunofluorescence Mycobacterium tuberculosis Biosensor AC electroosmosis Capillary action
The authors acknowledge the support of a CDC contract (200-2007-M-22794, Program Manager: David A. Wilson at Division of TB Elimination/Nat. Center for HIV, Viral Hepatitis, STD & TB/Centers for Disease Control and Prevention).
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