Novel Double-Potential Electrochemiluminescence Ratiometric Strategy in Enzyme-Based Inhibition Biosensing for Sensitive Detection of Organophosphorus Pesticides

Generally, electrochemiluminescence (ECL) ratiometric assays were based on the energy transfer (ET) between an emitter and a metal nanomaterial or between two different emitters. The choice of suitable energy donor–acceptor pair and the distance dependence of ET would greatly limit the practical application of ratiometric assays. This work explored a novel double-potential ECL ratiometry without the ET for organophosphorus pesticides (OPs) analysis, in which, reduced graphene oxide-CdTe quantum dots (RGO-CdTe QDs) and carboxyl-conjugated polymer dots (PFO dots) were chosen as cathodic and anodic ECL emitters, and the reactant (dissolved O2) and the product (H2O2) in enzymatic reactions served as their coreactants, respectively. With the occurrence of the enzymatic reactions induced by the acetylcholinesterase (AChE) and choline oxidase (ChOx), the cathodic ECL signal from RGO-CdTe QDs was at "signal off" state due to the consumption of dissolved O2. Meanwhile, the anodic ECL signal from PFO dots was at "signal on" state due to the in situ generation of H2O2. In the presence of OPs, the cathodic ECL signal would increase while the anodic ECL signal would decline correspondingly due to the inhibition of OPs on the activity of AChE. Using the reactant and the product in enzymatic reactions as the coreactants of two different ECL emitters, we conveniently achieved the opposite change trend in two ECL signals for the ratiometric detection of OPs, which exhibited a greatly improved accuracy, reliability and sensitivity, thus, showing a great attraction for developing ECL ratiometric systems for the bioanalysis.