Electrochemical immunosensor for detecting the spore wall protein of Nosema bombycis based on the amplification of hemin/G-quadruplex DNAzyme concatamers functionalized Pt@Pd nanowires.

In this work, an ultrasensitive electrochemical immunosensor for detecting the Pebrine disease related spore wall protein of Nosema bombycis (SWP N.b) was fabricated based on the amplification of hemin/G-quadruplex functionalized Pt@Pd nanowires (Pt@PdNWs). The synthesized Pt@PdNWs possessed large surface area, which could effectively improve the immobilization amount of hemin/G-quadruplex DNAzyme concatamers produced via hybridization chain reaction (HCR). In the presence of SWP N.b, the hemin/G-quadruplex labeled Pt@PdNWs bioconjugations was captured on electrode surface and thus obtained electrochemical signal. After the addition of NADH into the electrolytic cell, hemin/G-quadruplex firstly acted as an NADH oxidase to locally produce H2O2 in the presence of dissolved O2. Then, the generated H2O2 would be quickly reduced via hemin/G-quadruplex as a horseradish peroxidase mimicking (HRP-mimicking) DNAzyme, which finally promoted the self-redox reaction of hemin/G-quadruplex and a greatly enhanced electrochemical signal was obtained. Furthermore, Pt@PdNWs with excellent electrocatalytic performance could also amplify electrochemical signal. With these amplification factors, the electrochemical immunosensor exhibited a wide linear range from 0.001 ng mL(-1) to 100 ng mL(-1) with a detection limit (LOD) of 0.24 pg mL(-1), providing a new promise for the diagnosis of Pebrine disease.