Highly amplified electrochemiluminescence of peroxydisulfate using bienzyme functionalized palladium nanoparticles as labels for ultrasensitive immunoassay

An immunosensor based on the electrochemiluminescence (ECL) of peroxydisulfate was firstly proposed by coupling the cooperation of two enzymes to in situ generate coreactant with palladium nanoparticles (PdNPs) as catalyst for the ECL reaction. PdNPs were previously synthesized, which successfully attached to functional carbon nanotubes (FCNTs), to bind the secondary antibody and bienzyme (horseradish peroxidase and glucose oxidase). Then the prepared bioconjugates were introduced to the electrode via sandwich immunoreactions. Accordingly, a dramatically amplified ECL signal was obtained for that GOD catalyzed glucose to produce H2O2 which was subsequently reduced by HRP to in situ generate O2, then PdNPs as catalyst for the ECL reaction of peroxydisulfate/O2. The present immunosensor was used to detect α-1-fetoprotein (AFP) and showed a wide linear range of 1×10−5–100 ng mL−1, with a low detection limit of 3.3 fg mL−1(S/N=3). This new signal amplification strategy for preparation of the ECL immunosensor could be easily realized and has a potential application in ultrasensitive bioassays.

► Peroxydisulfate/O2 based ECL system has been applied in ultrasensitive bioassays.
► Bienzyme-based strategy for generating coreatant in situ to improve the sensitivity.
► With PdNPs as catalyst to further amplify the ECL signal.