Sensitive and Quantitative Determination of Cardiac Troponin I Based on Silica-Encapsulated CdSe/ZnS Quantum Dots and a Fluorescence Lateral Flow Immunoassay

Cardiac troponin I is generally used as a biomarker of myocardial infarction or acute myocardial infarction. A timely and rapid diagnosis method for cardiac troponin I is of great importance. In this paper, a novel CdSe/ZnS quantum dot (QD) based fluorescence lateral flow immunoassay (QD-LFIA) is reported for the rapid and quantitative detection of cardiac troponin I in human serum. The water-soluble silica-encapsulated QDs (QDs@SiO₂) serve as a new fluorescent probe and an economical, portable, quantitative instrument was used for the first time to detect cardiac troponin I antigen. By using the optimized immunoassay procedure with clinical samples, cardiac troponin I was determined in 10 min with high sensitivity (as low as 5.6 × 10⁻³ ng/mL), broad linear range (0.8–200 ng/mL), and good precision (the coefficient of variation was less than 10%). The comparison of this new QD-LFIA and a standard direct chemiluminescence assay demonstrated that the former platform was rapid, low-cost, and sensitive. It may be further applied to the quantitative determination and monitoring of cardiac troponin I levels in clinical use.