A ratiometric fluorescent sensor based on metalloenzyme mimics for detecting organophosphorus pesticides

Organophosphorus pesticides (OPs) have threatened food safety and environmental security. Establishing an easy-to-operate, fast, and real-time sensor for OPs is an inevitable trend. Here metalloenzyme mimics of metal-bonding peptides were designed and the optimal metalloenzyme mimic was combined with QDs (Carbon QDs (CQDs) and CdTe QDs) to construct a visible ratiometric fluorescent probe to detect OPs. There were two functional fragments comprised in this sensing system: the Zn2+-bonding peptides behaved as enzyme mimics and were used to recognize and hydrolyze OPs to produce p-Nitrophenol (PNP), while fluorescent QDs were used as an indicator of PNP. The two kinds of QDs were organized and the CdTe QDs acted as the sensor and CQDs served as an interior reference for OPs’ sensing. With increasing the amounts of OPs, the fluorescence of the biosensor changed from red to blue. The detection limit of OPs (e.g., methyl paraoxon) can reach 35 nM. The activity of metal-bonding peptides was obviously improved by altering the peptide sequence, thus shortening the detection time and improving the sensor sensitivity. The dosage-sensitive, broad-chromatic, and bifunctional method established in this work can be applied in real samples and opened a window toward peptide-immobilized formats and real-time detection of OPs.