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.
Keywords: POCT; cardiac markers; immunochromatography; magnetic nanobeads.