A dry chemistry-based ultrasensitive electrochemiluminescence immunosensor for sample-to-answer detection of Cardiac Troponin I.

Dry chemistry-based fluorescence or colorimetric immunosensors have been widely applied for point-of-care testing (POCT). However, dry chemistry-based electrochemiluminescence (ECL) immunosensors have not been reported for real sample-to-answer detection. Herein, a dry chemistry-based sample-to-answer, ultrasensitive closed bipolar electrode-ECL (CBP-ECL) immunosensor based on lateral flow assay has been firstly designed for POCT of Cardiac Troponin I (cTnI). The CBP-ECL immunosensor consisted of a fiber material-based chip and an outer shell, which were easily and affordably fabricated by screen-printing and 3D printing, respectively. Additionally, the Ru(Ⅱ)-L-Cys composite, as a self-enhanced ECL probe, was firstly introduced into the sandwich CBP-ECL immunosensor. The ECL signal generated by labeled antibody functionalized Ru(Ⅱ)-L-Cys could quantify cTnI sensitively. Therefore, the immunosensor had a wide linear range (0.001-100 ng/mL) and acceptable sensitivity (0.4416 pg/mL), together with superior specificity and good reproducibility and stability. Furthermore, the immunosensor was capable of detection of cTnI in serum, with recoveries of 97.3-103.4%. For detection of cTnI in plasma samples, the results of the proposed CBP-ECL had a good correlation with those of the clinical method. Importantly, the analysis process easily operated, and completed in 7 min. These results illustrated that the proposed immunosensor effectively combined the high sensitivity of CBP-ECL with the simplicity of lateral flow assay, and provided a promising POCT avenue for early diagnosis of acute myocardial infarction (AMI) and other diseases.