Immunosensor for rapid detection of human cardiac troponin I, a biomarker for myocardial infarction

A rapid detection approach based on quench-release for cardiac troponin I (cTnI), a biomarker of myocardial infarction, was developed. To ensure detection accuracy, a rabbit monoclonal antibody, RabMG4C80A (G4), that binds specifically to cTnI was used. The antigen-binding fragment of G4 was prepared and labeled with fluorescent dyes to produce a fluorescent immunosensor G4 Q-body that can be used for cTnI detection. Using this method, an assay could be completed in as little as 5 min, enabling rapid diagnosis following myocardial infarction and providing a timely basis for patient treatment. A dose-response curve of the G4 Q-body for cTnI detection was obtained from the fluorescence spectra, from which the concentration of cTnI in the sample was determined. The limits of detection and concentration for 50% of maximal effect of the assay were found to be below 10 pM and 3.8 nM, respectively, of cTnI. The optimal detection range was 10 pM-1000 nM. After the occurrence of acute myocardial infarction, the cTnI concentration rose to 2 nM in 1 h and persisted for 6-8 days at around 20 nM; the detection range of the assay therefore covered the clinically relevant range of cTnI during myocardial infarction. This is the first Q-body based on rabbit monoclonal antibodies, and it is expected to contribute to the rapid diagnosis and precise treatment of myocardial infarction.