Rapid and sensitive cardiac troponin I immunoassay based on fluorescent europium(III)-chelate-dyed nanoparticles

Abstract

BackgroundCardiac troponins are the preferred and recommended biomarkers of myocardial infarction. Unfortunately, most of the current commercial assays do not meet the guideline recommendations for sensitivity and low-end precision. Therefore, improvements in their analytical performance are still needed. MethodsCardiac troponin I (cTnI) immunoassay was developed. The assay utilized a monoclonal antibody and a F(ab')2 antibody fragment immobilized onto the microtiter wells for capturing, and a monoclonal antibody covalently conjugated to fluorescent europium(III)-chelate-dyed nanoparticles for detecting. Following a 15-min incubation of the sample and nanoparticle-bioconjugates in the capture wells, cTnI was quantified directly from the washed well surface by time-resolved fluorometry. ResultsThe limits of detection and quantification were 0.0020μg/l and 0.012μg/l, respectively. The response was linear in the measured range of 0.003–9.6μg/l. The within-run imprecisions were 9.8, 5.1, 7.7 and 5.4%, and the total imprecisions were 13.1, 10.4, 9.0 and 8.7% at cTnI levels of 0.007, 0.051, 0.52 and 2.62μg/l, respectively. Plasma recoveries of added cTnI were 72–119%. Regression analysis with Innotrac Aio! 2nd generation cTnI assay yielded a slope (95% confidence intervals) of 1.197 (1.141 to 1.253) and y-intercept of 0.216 (−0.128 to 0.561)μg/l (Syx=2.176μg/l, n=212, r=0.945). ConclusionsThe developed immunoassay based on europium(III)-chelate-dyed nanoparticle label allows rapid and sensitive measurement of cTnI.