Zhang_2023_J.Agric.Food.Chem_71_11884

Herein, we constructed a label-free ratiometric fluorescence biosensing strategy for the determination of butyrylcholinesterase (BChE) activity and organophosphorus (OPs) concentration. BChE promoted the hydrolysis of iodized s-butyrylthiocholine (BTCh) into a reducing substance thiocholine, which can decompose CoOOH nanosheets (CoOOH NSs) to Co(2+). Subsequently, the single-stranded DNA (ssDNA) on the surface of CoOOH NSs was released. Then, ssDNA hybridized with hairpin DNA (h-DNA) and triggered the target recycling amplification process, producing large amounts of G-quadruplex. After adding thioflavin T (ThT), the target BChE was converted into activatable G-quadruplex/ThT with an amplified yellow fluorescence signal. The addition of OPs could significantly inhibit the hydrolysis of BTCh by BChE and thus unable to produce the yellow fluorescence G-quadruplex/ThT complex. Throughout the entire process, the fluorescence intensity of Hg-ZnSe QDs as a reference signal remained unchanged at 630 nm. Furthermore, this work provided an effective approach for detecting the BChE activity in serum samples and OPs in fruits and vegetables.