Increase in the detection sensitivity of a lateral flow assay for a cardiac marker by oriented immobilization of antibody

Abstract

Early detection of human cardiac markers is regarded as a gold standard for diagnosis of acute myocardial infarction (AMI). Here we demonstrate the increase in the detection sensitivity of a lateral flow assay for a cardiac marker troponin I (cTnI) by oriented immobilization of antibodies on magnetic beads. For the construction of sensitive magnetic labels, orientated-immobilization of anti-troponin I antibodies on magnetic beads was attempted using protein G. Magnetic beads were first conjugated with protein G followed by immobilization of anti-cTnI antibodies. The factors affecting the detection sensitivity in the lateral flow assay system were investigated. The lateral flow assay of cTnI was carried out using the magnetic beads and a Giant magnetoresistive (GMR) sensor at the optimized conditions, and compared the results with using a conventional random immobilization method. Magnetic labels with oriented immobilization of antibodies enabled the detection of cTnI up to 0.01 ng/mL, showing significantly increased sensitivity compared with conventional immobilization method. This result clearly shows that the magnetic labels with oriented immobilization of antibodies can find wide applications in the lateral flow assays of target analytes.