The cohesion of cascade enzyme reaction with metal-organic framework composite for the sensitive detection of malathion and in-situ imaging of vegetables

The high residual nature of organophosphorus pesticides poses a potential risk to the environment and human health through bioaccumulation. Herein, by using Fe3O4 nanoclusters (NCs) as the nucleation center and polyvinyl pyrrolidone as the stabilization layer, Cu-based metal-organic frameworks (Cu-MOFs) were directly grown around Fe3O4 NCs to form core-shell Fe3O4@Cu-MOFs composites (FCF). Then, the fluorescence properties of FCF were used to construct a fluorescence biosensor for the detection of organophosphorus pesticide residues in vegetables. The bi-enzyme function between acetylcholinesterase and choline oxidase can produce hydrogen peroxide, which can oxidize ferrous ions to ferric ions thus influencing the fluorescence of FCF. Based on the ability of malathion pesticides to inhibit acetylcholinesterase activity, the biosensor demonstrated a linear relationship between the fluorescence intensity and the concentration of the malathion in the range of 5 ng/mL to 50 μg/mL with a detection limit of 4.2 ng/mL. Furthermore, the FCF was combined with agarose gels to realize the visualization detection of malathion. This novel fluorescent nanocomposite offers promising applications for the visual detection of malathion and in situ imaging of vegetables, establishing a new pathway to develop high-performance fluorescent materials for environmental and food safety.