Capsulation of AuNCs with AIE Effect into Metal-Organic Framework for the Marriage of a Fluorescence and Colorimetric Biosensor to Detect Organophosphorus Pesticides

Organophosphorus pesticides (OPs) can inhibit the activity of acetylcholinesterase (AChE) to induce neurological diseases. It is significant to exploit a rapid and sensitive strategy to monitor OPs. Here, a metal-organic framework (MOF) acted as a carrier to encapsulate AuNCs, which can limit the molecular motion of AuNCs, trigger the aggregation-induced emission (AIE) effect, and exhibit a strong fluorescence with a fluorescence lifetime and quantum yield of 6.83 mu s and 4.63%, respectively. Then, the marriage of fluorescence and colorimetric signals was realized on the basis of the dual function of the enzymolysis product from AChE and choline oxidase (CHO) on AuNCs@ZIF-8. First, it can decompose ZIF-8 to weaken the restraint on AuNCs, and thus the fluorescence receded. Second, it can be used as a substrate for the peroxidase mimics of the released AuNCs to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) and a visible blue appeared. Thus, on the basis of the inhibition of AChE activity by OPs, a fluorescence-colorimetric dual-signal biosensor was established. In addition, colorimetric paper strips were exploited to realize a visual semiquantitative detection, and a smartphone APP was developed to make the visualization results more precise and realize real-time supervision of pesticide contamination.

Automated summary

A fluorescence-colorimetric dual-signal biosensor was developed for monitoring organophosphorus pesticides by encapsulating AuNCs in a metal-organic framework. This biosensor combines fluorescence and colorimetric signals based on the enzymolysis product of AChE and CHO, allowing detection through the inhibition of AChE activity. Additionally, colorimetric paper strips and a smartphone APP were utilized for visual semiquantitative detection and real-time supervision of pesticide contamination.