Development of a simple enzyme-linked hybrid-sandwich assay for sensitive detection of cardiac troponin I

Abstract

This work reports a simple enzyme-linked hybrid-sandwich assay (ELHSA) for one vital cardiac biomarker, cardiac troponin I (cTnl). Aimed at expanding the “antibody-antigen” immunoassay, a distinct “capture antibody-target-detection aptamer” configuration was designed, in which two types of recognition elements were involved. Through systematical study, optimal antibody-aptamer combination and amount ratio between streptavidin-horseradish peroxidase conjugate and biotin-modified aptamer were obtained, and a beneficial interaction mode between cTnI and the two recognition elements was disclosed, namely, cTnI protein binding to the aptamer could be well recognized by antibody, but not vice versa. Moreover, it was first found that, apart from as a blocking agent, bovine serum albumin could be introduced in the detection probe solution as an enhancer, leading to high sensitivity and reproducibility. The BSA-assisted ELHSA can detect as low as 0.24 ng/mL cTnI and is a new, simple and effective strategy to apparently improve ELHSA for cTnI detection. Meanwhile, prominent selectivity derived from dual specific recognition elements and good applicability indicate that the developed ELHSA for cTnI is anticipated to substitute classical ELISA for diagnosis of cardiovascular diseases in the future.