Ceria Doped Zinc Oxide Nanoflowers Enhanced Luminol-Based Electrochemiluminescence Immunosensor for Amyloid-β Detection

In this work, ceria doped ZnO nanomaterials with flower-structure (Ce:ZONFs) were prepared to construct a luminol-based electrochemiluminescence (ECL) immunosensor for amyloid-beta protein (A beta) detection. Herein, carboxyl groups ( COOH) covered Ce:ZONFs were synthesized by a green method with lysine as reductant. After that, Ce:ZONFs-based ECL nano composite was prepared by combining the luminophore of luminol and Ce:ZONFs via amidation and physical absorption. Luminol modified on Ce:ZONFs surface could generate a strong ECL signal under the assistance of reactive oxygen species (ROSs) (such as OH center dot and O-2(center dot-)), which were produced by a catalytic reaction between Ce:ZONFs and H2O2. It was worth noticing that a quick Ce4+ <-> Ce3+ reaction in this doped material could increase the rate of electron transfer to realize the signal amplification. Subsequently, the luminol functionalized Ce:ZONFs (Ce:ZONFs-Lum) were covered by secondary antibody (Ab(2)) and glucose oxidase (GOD), respectively, to construct a novel Ab(2) bioconjugate (Ab(2)-GOD@Ce:ZONFs-Lum). The wire-structured silver-cysteine complex (AgCys NWs) with a large number of -COOH, which was synthesized by AgNO3 and L-cysteine, was used as substrate of the immunosensor to capture the primary antibody (Ab(1)). Under the optimal conditions, this proposed ECL immunosensor had exhibited high sensitivity for A beta detection with a wide linear range from 80 fg/mL to 100 ng/mL and an ultralow detection limit of 52 fg/mL. Meanwhile, this biosensor had good specificity for A beta, indicating that the provided strategy had a promising potential in the detection of A beta.