Dual signal amplification of zinc oxide nanoparticles and quantum dots-functionalized zinc oxide nanoparticles for highly sensitive electrochemiluminescence immunosensing

A novel electrochemiluminescence (ECL) immunosensor for highly sensitive detection of α-fetoprotein (AFP) based on a dual signal amplification strategy was developed. Zinc oxide (ZnO) nanoparticles were employed as the carriers for immobilizing the capture AFP antibody (Ab1) and CdSe quantum dots (QDs). CdSe QDs-functionalized ZnO nanoparticles were used as the tracer to label the signal AFP antibody (Ab2). CdSe QDs-functionalized ZnO nanoparticles were prepared through an amide dehydration reaction and they were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The Ab2 was bound to the CdSe QDs-functionalized ZnO nanoparticles to obtain the detection probe. ZnO nanoparticles could accelerate electron transfer between the detection probe and the electrode, and their large surface area was beneficial for loading more CdSe QDs, leading to an enhanced ECL signal (0.9-fold increase) by a sandwich immunoreaction. This also indicated efficient association of the detection probe on the immunosensor surface. The designed immunoassay showed a wide linear range from 0.5 to 600 ng mL−1 with a detection limit of 0.48 ng mL−1 at a S/N ratio of 3 for AFP detection. The ECL immunosensor exhibited good analytical performance and was successfully applied to clinical sample detection, showing a promising application in ECL biosensing.