Novel electrochemical immunosensor for sensitive monitoring of cardiac troponin I using antigen-response cargo released from mesoporous Fe3O4.

A novel controlled release system-based antigen-response electrochemical immunosensor was developed for detecting cardiac troponin I (cTnI) by using aminated polystyrene microsphere (APSM) as molecular gate and Fe3O4 as nanocontainer. The amino functionalized mesoporous Fe3O4 (Fe3O4-NH2) was used to load cobalt phthalocyanine nanoparticles (CoPc NPs) and further capture the antibody of cTnI (Ab) to form Fe3O4-Ab. In addition, APSM was introduced to cap on the mesoporous of Fe3O4-Ab by electrostatic interaction. With the addition of cTnI, APSM was separated from Fe3O4-Ab due to the specific binding of antibody to antigen. Then, CoPc NPs were released from the mesoporous. The experimental results revealed that CoPc NPs showed superb catalytic performance when catalyzing hydrogen peroxide (H2O2) reduction in phosphate buffer saline (PBS). The current responses are correlated with the amount of cTnI. Under the best conditions, a broad linear range from 1.0 pg/mL to 100 ng/mL with a low detection limit of 0.39 pg/mL (S/N = 3) was obtained. The immunosensor also shows good reproducibility and selectivity, which endows its broad application prospect in clinical research.