High-sensitivity cardiac troponins I sandwich assay by immunomagnetic microparticle and quantum dots

Objective High-sensitivity cardiac troponins I (hs-cTnI) has been endorsed as a standard biomarker for diagnosis of acute myocardial infarction (AMI) and can provide information for risk stratification. Our study aimed to develop a quantum-dot-labeled magnetic immunoassay for the hs-cTnI detection. Methods We developed a novel immunomagnetic microparticle and quantum dots-based sandwich assay (QM-cTnI) that employs digital recording of fluorescence. Immunomagnetic microparticle conjugated with two monoantibodies was used as capture antibody, and two biotinylated monoantibodies were used as detection antibody, then quantum dots conjugated streptavidin served as a fluorescence bioprobe and the signal was recorded by the luminescence spectrometer. Results Hs-cTnI was quantifiable in serum within one hour in the QM-cTnI assay which has a detection limit of 0.047 ng/mL and the effective measuring range was 0–40 ng/mL. The intra-assay and interassay coefficients of variation were 8.56% and 8.92% at 0.2 ng/mL, 5.83% and 7.66% at 4 ng/mL, and 6.21% and 8.76% at 20 ng/mL, respectively. All of the recovery rates were within the range of 98.11–101.89% and the average recovery rate was 99.69%. This assay performed well compared with FDA-approved SIEMENS ADVIA Centaur XP immunoassay system by 104 patient serum samples (R 2 = 0.9951). High-concentration interferents (bilirubin, triglycerides, and hemoglobin) did not influence the test results indicating good specificity of the MQ-cTnI assay. Conclusion Our results demonstrated that hs-cTnI sandwich assay with the immunomagnetic microparticle and quantum dots-based multi-mAb approach is a sensitive, accurate, and quantitative method for the detection of disease biomarkers.