Electrochemical impedimetric detection of stroke biomarker NT-proBNP using disposable screen-printed gold electrodes

Stroke is the second top leading cause of death globally. It is caused by an abrupt interruption of blood flow to the brain. In that course, brain natriuretic peptide (BNP) and its derivative N-terminal pro b-type natriuretic peptide (NT-proBNP), neurohormones produced mainly by the heart ventricles in response to excessive stretching of cardiomyocytes (heart muscle cells), are proven to be good biomarkers for heart failure diagnosis. Moreover, there is growing clinical interest of the use of NT-proBNP for stroke diagnosis and prognosis because it is significantly associated with cardioembolic stroke and secondary stroke reoccurrence, with sensitivity >90% and specificity >80%. However, in diagnostic settings, there is still a need to address the encountered analytical problems, particularly assay specificity and set up. In this study, a novel approach for NT-proBNP detection is demonstrated using an electrochemical immunoassay method. A label-free impedimetry immunosensor for stroke biomarker was developed using modified disposable screen-printed gold electrodes (SPGE) hosting specific anti-NT-proBNP capture antibody. The performance of our immunosensor was studied in the presence of NT-proBNP in both buffered and mock (porcine) plasma samples. A linear relation between the relative total resistance (ΔR_tot) responses and the NT-proBNP concentrations in buffer was observed in a range from 0.1 to 5 ng mL^-1 with a correlation coefficient (R2) of 0.94656. Overall, the biosensor has demonstrated the capability to quantitate NT-proBNP and differentiate such concentrations in a low concentration range, especially among 0, 0.1, 0.5, 1, and 3 ng mL^-1 in plasma samples within 25 min. This range is valuable not only for classifying cardioembolic stroke (higher or equal to 0.5 ng mL^-1), but also predicting the risk of secondary stroke reoccurrence (higher than 0.255 ng mL^-1). Our biosensor has the potential to be used as an easy-to-use point-of-care test that is both accurate and affordable.