title: Lab-on-a-drop: biocompatible fluorescent nanoprobes of gold nanoclusters for label-free evaluation of phosphorylation-induced inhibition of acetylcholinesterase activity towards the ultrasensitive detection of pesticide residues.
abstract: A simple, sensitive, selective, and "lab-on-a-drop"-based fluorimetric protocol has been proposed using biocompatible fluorescent nanoprobes of gold nanoclusters (AuNCs) for the label-free evaluation of the catalytic activity and phosphorylation of acetylcholinesterase (AChE) under physiologically simulated environments. Protein-stabilized AuNCs were prepared and mixed with acetylthiocholine (ATC) serving as "a drop" of fluorimetric reaction substrate. The AChE-catalyzed hydrolysis of ATC releases thiocholine to cause the aggregation of the AuNCs towards a dramatic decrease in fluorescence intensities, which could be curbed by the phosphorylation-induced inhibition of AChE activity when exposed to organophosphorus compounds (OPs). The reaction procedures and conditions of AChE catalysis and phosphorylation were monitored by fluorimetric measurements and electron microscopy imaging. Moreover, a selective and ultrasensitive fluorimetric assay has been tailored for the detection of pesticide residues using dimethyl-dichloro-vinyl phosphate (DDVP) as an example. Investigation results indicate that the specific catalysis and irreversible OP-induced phosphorylation of AChE, in combination with sensitive fluorimetric outputs could facilitate the detection of total free OPs with high selectivity and sensitivity. A linear concentration of DDVP ranging from 0.032 nM to 20 nM could be obtained with a detection limit of 13.67 pM. Particularly, pesticide residues of DDVP in vegetable samples were quantified down to ~36 pM. Such a label-free "lab-on-a drop"-based fluorimetry may promise wide applications for the evaluation of the physiological catalytic activity of various enzymes (i.e., cholinesterase), and especially for monitoring the direct phosphorylation biomarkers of free OPs towards rapid and early warning, and accurate diagnosis of OP exposure.
authors: Shandong Province Key Laboratory of Life-Organic Analysis, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu City, Shandong Province 273165, P. R. China. huawangqfnu@126.com.
authors: Ning
authors: N
authors: Zhang
authors: Yanmei
authors: Y
authors: Si
authors: Zongzhao
authors: Z
authors: Sun
authors: Shuai
authors: S
authors: Li
authors: Shuying
authors: S
authors: Li
authors: Yuehe
authors: Y
authors: Lin
authors: Hua
authors: H
authors: Wang
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D004006:Dichlorvos / Q000032:analysis* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry*; D005470:Fluorometry / Q000295:instrumentation*; D006046:Gold / Q000737:chemistry*; D057230:Limit of Detection; D049329:Nanostructures / Q000737:chemistry*; D010573:Pesticide Residues / Q000032:analysis* / Q000378:metabolism; D010766:Phosphorylation; D014675:Vegetables / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D010573:Pesticide Residues; D006046:Gold; D004006:Dichlorvos; D000110:Acetylcholinesterase