Enzymatic reaction modulated synthesis of quantum dots for visual detection of cholinesterase activity and inhibitor

An enzyme-activable modulated synthesis of fluorescent CdTe quantum dots (QDs) strategy was developed in this work. Monitoring the in-situ growth of CdTe QDs is shown to be a novel route to label-free and visual detect butyrylcholinesterase (BChE), an important enzyme in human bodies. BChE can catalyze butyrylcholine (BTCh) to produce thiocholine (TCh), which is an excellent thio-ligand during CdTe QDs growths. Therefore, BChE can activate the thio-ligand via enzymolysis thus trigger the growth of luminescent QDs. As the BChE concentration was proportional to the fluorescence intensity of the QDs, the activity of BChE was detected accordingly. Under the optimized experimental conditions, the limit of detection (LOD) of BChE was found to be 0.96 U L-1. The relative standard deviation (RSD) (n = 7) was 1.8%. What's more, parathion, one of the organophosphorus pesticides (OPs), which inhibits the activity of BChE, was used to prevent the generation of thiocholine and therefore inhibits the growth of QDs. As a result, this sensing system can also present a turn off mode for the parathion detection with highly sensitivity (LOD = 0.38 ng mL(-1)). Furthermore, visual detection was realized for BChE and parathion in this strategy, 40 U L-1 of BChE and 2 ng mL(-1) of parathion can be discriminated from the blank solution with the naked eye, respectively.