One-step potentiometric immunoassay for plasma cardiac troponin I using antibody-functionalized bis-MPA-COOH dendrimer as competitor with improved sensitivity
Herein, we report on a new one-step potentiometric immunoassay for the sensitive and specific detection of human plasma cardiac troponin I (cTnI) for cardio-cerebrovascular diseases. Initially, cTnI biomolecules were immobilized on the surface of gold nanoparticles-functionalized screen-printed graphite electrode (SPGE). Thereafter, rabbit polyclonal to cTnI antibodies were covalently conjugated to bis-MPA-COOH dendrimer through a typical carbodiimide coupling. Introduction of target analyte caused a competitive immunoreaction between the immobilized cTnI on the electrode and the conjugated antibody on the denderimer. The potentiometric measurement mainly derived from the change in the surface charge on the surface of the modified electrode thanks to the negatively charged bis-MPA-COOH dendrimers before and after the immunoreaction. With the increasing target cTcI, the captured dendrimers to the immunosensor decreased, thereby resulting in the change of the electric potential. Under optimum conditions, the potentiometric immunosensor exhibited a good potentiometric responses for the detection of cTcI, and allowed determination of target analyte at a concentration as low as 7.3 pg mL-1. An intermediate precision of ≤8.7% was accomplished with the batch-to-batch identification. Meanwhile, the potentiometric immunosensor gave good anti-interferring capacity and selectivity against other proteins or biomarkers. Importantly, our system displayed a high method accuracy for analysis of human plasma serum samples containing target cTcI relative to the commerical human cTcI enzyme-linked immunosorbent assay (ELISA) kits.