A potentiometric immunosensor based on silver nanoparticles decorated ZnO nanotubes, for the selective detection of d-dimer

In this study, a new, simple, fast and highly sensitive potentiometric immunosensor for the selective detection of d-dimer is developed using silver nanoparticles decorated ZnO nanotubes. The d-dimer is a biomarker and found at high levels in the human body when it suffers from deep vein thrombosis (DVT) disorders. ZnO nanotubes were obtained by the chemical etching of nanorods using a hydrothermal method. The silver nanoparticles were deposited on the ZnO nanotubes using an electrodepositing technique. The structure and the composition characterization was measured by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques respectively. The ZnO nanorods are perpendicular to the substrate with uniform distribution. The etching of the nanorods into nanotubes is almost complete and the nanotubes are fully covered with silver nanoparticles. The mouse anti human d-dimer antibody was immobilized on the silver nanoparticles decorated ZnO nanotubes for the selective detection of d-dimer. The potentiometric immunosensor has shown a highly sensitive and linear response for the wide range of 1.00 x 10(-5)-1.00 x 10(0) mu g/ml d-dimer concentrations prepared in the phosphate buffer solution of pH 7.4. The presented d-dimer biosensor exhibited a detection limit of 1.00 x 10(-6) mu g/ml. The antibody immobilized immunosensor presents a fast response time of less than 5 s with acceptable selectivity, reproducibility and storage stability. The observed performance of the developed immunosensor demonstrates the high usability for the selective detection of the d-dimer from clinical and real samples. (C) 2013 Elsevier B.V. All rights reserved.