High performance immunochromatographic assay for simultaneous quantitative detection of multiplex cardiac markers based on magnetic nanobeads

The detection of cardiac markers is critical to the diagnosis of acute myocardial infarction, and immunochromatographic assays are a common tool for point-of-care analysis. Methods: We report a multiplexed lateral flow test strip for simultaneous quantitative detection of cardiac troponin I (cTnI), creatine kinase isoenzyme MB (CKMB), and myoglobin (Myo). Hydrophilic, monodisperse, stable, and carboxyl-modified (COOH-) magnetic nanobeads (MNBs) were used to construct immunomagnetic probes specific to the three cardiac markers. The detection area of the sandwich-style complexes contained three test lines for cTnI, CKMB, and Myo. The magnetic signal intensity of the detection area in the nitrocellulose membrane was measured via a magnetic immunochromatography reader developed in house. Results: To optimize the assay, a modified working buffer was also investigated to improve the detection sensitivity, decrease the background noise, and shorten the detection time. The MNB-based immunochromatography test (MICT) strip offers a wide linear dynamic detection range, rapid detection, high sensitivity, and specificity. The limit of detection was 0.0089 ng/mL for cTnI, 0.063 ng/mL for CKMB, and 0.05 ng/mL for Myo with minimal cross-reactivity. There were 110 clinical human serum samples that were used to evaluate this platform with high correlation. Conclusion: MICT shows great potential as a supplemental method for in vitro diagnostics in the laboratory or in other point-of-care testing (POCT) applications.