An enzyme-free electrochemical immunoassay is described for the neutrophil gelatinase-associated lipocalin (NGAL; a biomarker of kidney disease). Prussian Blue (PB) nanoparticles with redox activity were deposited on graphitic C3N4 nanosheets (g-C3N4) by in-situ reduction. A screen printed electrode (SPCE) was modified with antibody against NGAL, and the PB-g-C3N4 nanohybrid was used as the signal-generating tag for the secondary antibody against NGAL. Upon addition of target NGAL and of secondary antibody, a sandwich is formed on the SPCE. At an applied potential of typically 0.13 V (vs. Ag/AgCl), a well-defined voltammetric peak is observed that results from the presence of PB on the secondary antibody. Under optimal conditions, the peak current increases linearly in the 0.01 to 10 ng·mL-1 NGAL concentration range, and the detection limit is 2.8 pg·mL-1. An average precision of <12% was accomplished in the batch-to-batch mode. Other disease-related biomarkers do not interfere. The accuracy and inter-laboratory validation of this method were evaluated for target NGAL detection in spiked human serum by using a commercial ELISA. The results obtained by the two methods are in good accordance. Graphical abstract An enzyme-free electrochemical immunoassay was used for detection of neutrophil gelatinase-associated lipocalin by Prussian blut/graphitic-C3N4 nanohybrids as the signal-generation tags.
Keywords: Human serum specimens; Kidney biomarker; Method accuracy; Scanning electron microscopy; Transmission electron microscopy.