Enzyme-immobilized metal-organic framework biosensor for target-triggered sensitive fluorescence detection of diazinon residue and accumulation in rice

Abstract

Developing rapid and sensitive analytical methods for detecting diazinon residue in agricultural products is necessary for food safety surveillance. Herein, we developed a urease modified Zr-centered metal–organic framework (ZrMOF@urease) nanosensor for detecting diazinon accumulation in crops. ZrMOF@urease was synthesized through rational immobilization of urease on the scaffold of ZrMOF to achieve a robust biocatalyst with significant enhancement in enzyme activity. The efficient hydrolysis of urea by ZrMOF@urease produced ammonia, which interacted with the terminal and bridging hydroxyl groups of the Zr₆ clusters. This interaction resulted in measurable fluorescence recovery. Furthermore, the presence of diazinon inhibited the enzyme-catalyzed reaction, generating variations in detectable fluorescence signals. The fluorescence sensor achieved a detection limit of 4.5 ng mL ⁻¹ against diazinon. High recovery rates from various real samples and stable bioaccumulation monitoring in rice highlighted the effectiveness and reliability of the biosensor. This enzyme-immobilized metal–organic framework (MOF) sensor not only offers valuable insights into the structure-activity relationship of enzyme-functionalized MOFs, but also promoted the application of MOF-based biosensors for rapid pesticide detection in environmental monitoring and agricultural management.