Ultrasensitive electrochemical strategy for NT-proBNP detection with gold nanochains and horseradish peroxidase complex amplification

A novel electrochemical immunosensor for sensitive detection of cardiac biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP) is fabricated based on the nanostructural gold and carbon nanotubes composite as desirable platform for the capture antibodies immobilization and gold nanochains (AuNCs) and horseradish peroxidase (HRP) complex labeled secondary antibodies (AuNCs-HRP-Ab2) for signal amplification. The gold nanochains were prepared by the employment of l-ascorbic acid (AA) as a mediator and template. With the surface area enhancement by nanostructural gold functionalized carbon nanotubes composite, the amount of immobilized primary antibodies (Ab1) can be enhanced. More importantly, enhanced sensitivity can be achieved by introducing the multibioconjugates of AuNCs-HRP-Ab2 onto the electrode surface through “sandwich” immunoreactions. The linear range extended from 0.02 to 100 ng/mL with a correlation coefficient of R = 0.997 and a limit of detection reaching 6 pg/mL at a signal-to-noise ratio of 3:1, which is well below the commonly accepted concentration threshold (0.1 ng/mL) used in clinical diagnosis. The specificity, regeneration and stability test demonstrated the feasibility of the developed immunoassay, which gives the attractive characteristics to be a candidate for the detection of NT-proBNP and other proteins of interest in both fundamental and applied research.