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

Abstract

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 μs 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.

Recent Progress in Metal-Organic Framework Based Fluorescent Sensors for Hazardous Materials Detection

“…By integrating the enzymolysis product from AChE and choline oxidase (CHO) on AuNCs@ZIF-8, a dual function probe with a fluorescence lifetime and quantum yield of 6.83 μs and 4.63% was obtained by Cai et al [ 120 ]. The authors used colorimetric strips constructed from the fluorescent material to visualise semi-quantitative detection.…”

Metal–Organic Frameworks-Mediated Assembly of Gold Nanoclusters for Sensing Applications

“…The tunable photoluminescence is one of the most attractive characteristic of AuNCs, which is beneficial to the development of sensitive luminescence sensing. MOF/AuNCs assemblies exhibit various advantages for enhanced sensitive and selective luminescence sensing on account of the improved properties [ 70 ]. For instance, the fluorescence intensity and lifetime of AuNCs are greatly increased in the assemblies, mainly because their nonradiative transition is attenuated due to the restriction of MOF structures [ 78 ].…”

“…These outstanding performances of MOF/AuNCs assemblies facilitate the sensitive colorimetric sensing of organophosphorus pesticides (OPs), acetylcholinesterase (AChE), choline oxidase (CHO), glucose, hydrogen peroxide, etc. [ 70 , 71 , 121 – 123 ].…”

“…The remarkable performance of MOFs inspired their integration with AuNCs, which endowed the MOFs-mediated AuNCs assemblies (MOF/AuNCs assemblies) with enhanced selectivity, sensitivity, regenerability, and recyclability for sensing. MOF/AuNCs assemblies, possessing distinct advantages compared to other reported AuNCs-based nanocomposites due to the unique performance of MOFs [ 12 , 77 ], have been proved to be a powerful analytical platform for luminescence sensing [ 65 – 69 ], colorimetric sensing [ 70 , 71 ], electrochemiluminescence sensing [ 72 , 73 ], and (photo)electrochemical sensing [ 74 – 76 ] (Fig. 1 ).…”

“…1 ). Diverse types of MOFs have been introduced for the fabrication of MOF/AuNCs assemblies, including materials of institute Lavoisier MOFs (MILs) [ 65 ], zeolitic imidazolate frameworks (ZIFs) [ 70 ], cyclodextrin-based MOFs (CD-MOFs) [ 71 ], and zirconium-coordinated MOFs (Zr-MOFs) [ 67 ]. The main advantageous features of MOF/AuNCs assemblies for sensing applications are as follows: Due to the protection of MOFs, the formation of MOF/AuNCs assemblies can significantly enhance the stability of AuNCs against the environmental perturbation.…”