Coreactant-free electrochemiluminescence biosensor for the determination of organophosphorus pesticides

Poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadazole)] (PFBT) was functionalized with carboxyl groups via nanoprecipitation method to prepare polymer nanoparticles (PNPs). Remarkable electrochemiluminescence (ECL) was observed at PFBT PNPs without any external species or dissolved O₂ as coreactants. Furthermore, such an ECL emission could be efficiently quenched by hydrogen peroxide (H₂O₂). A coreactant-free ECL enzyme-based biosensor is making use of PFBT PNPs as luminophore for detecting organophosphorus (OPs) pesticides. In the absence of OPs, H₂O₂ stemmed from the enzymatic reaction would quench the ECL signal of PFBT PNPs, resulting in an ECL signal-off state. In the presence of OPs, the ECL signal obviously increased because the enzyme activity of the acetylcholinesterase (AChE) was inhibited by OPs. The linear range for OPs detection was 1.0 × 10^-12-1.0 × 10^-7 M and the detection limit was low as 1.5 × 10^-13 M. Such a coreactant-free ECL strategy could avoid the drawbacks resulted from the addition of exogenous species or dissolved O₂ as coreactant. More importantly, H₂O₂ was released by many oxidases-induced reactions, and its quenching effect on the ECL of PFBT PNPs would pave a new avenue for constructing coreactant-free enzyme-based ECL biosensor for environmental monitoring and biological analysis.