Aim: To demonstrate a label-free electrical immunoassay for profiling vascular biomarker N-terminal pro-brain natriuretic peptide (NT-proBNP) associated with improved cardiac risk prediction.
Materials & methods: A high-density nanowell-based electrical immunoassay has been designed by integrating nanoporous aluminum oxide onto printed circuit board chips for the detection of NT-proBNP. The concentration of the biomarker is quantitatively determined by measuring impedance changes to the electrical double layer within the nanowells using electrochemical impedance spectroscopy. Detection sensitivity in the fg/ml range was obtained due to spatial confinement of the target biomarkers in size-matched nanowells.
Results & discussion: Electrical immunoassay performance was determined for the detection of NT-proBNP in phosphate-buffered saline (PBS) and human serum (HS). The lower limit of detection for the sensor was observed to be 10 fg/ml in PBS and 500 fg/ml in HS. The upper limit of detection was observed to be 500 fg/ml in PBS and 500 ng/ml in HS.
Conclusion: A label-free technique for detection of NT-proBNP at clinically relevant concentrations for evaluating cardiac risk is demonstrated. High sensitivity and specificity, robust detection and low volume (100 µl) per assay project the technology to be a successful competitor to traditional ELISA-based techniques.