| Organophosphorus compounds (OPs) are widely used in the agriculture all overthe world as pesticides and insecticides. The high toxicity of organophosphoruspesticides is ascribed to their ability to inhibit the activity of acetylcholinesterase(AChE),which is an essential enzyme to break down the neurotransmitteracetylcholine at cholinergic synapses. In order to avoid possible harm to humans andanimals,there has important significance to develop fast,sensitive and effectivemethods for in situ and online OPs detection.Currently,detection techniques in common use mainly includes instrumentalmethod and enzyme inhibition method.The instrumental method has a shortcoming ofcomplexity of the analysis process,needing professional technicians and Large-scaleexpensive equipment,and it’s not applicable of in situ and online detection.With therapid development of nanotechnology,various nano-materials have been widely appliedon biological detection field for its unique physical and chemical properties.For its highsensitivity,low cost and miniaturization which is convenient for in situ detection.Biosensor based on the nano-material is widely used in study of detection field.Quantum dot has become one of the most compelling topics in analytical chemistry forits advantage of high fluorescence intensity,narrow emission peak,high resistance tophotobleaching,and controllable emission peak spectrum.In this thesis,a highly sensitive method for detection of organophosphorus (OPs)pesticide based on gold quantum dots (Au QDs)-acetylcholinesterase (AChE)fluorescence quenching system was successfully constructed.The detectionmechanism is based on the fact that these pesticides can inhibit the activity ofAChE,thus preventing the generation of thiocholine,which can quench thefluorescence of Au QDs. By comparing the fluorescence intensity of Au QDs beforeand after addition of OPs,which could be brought out the quantitative detection ofOPs.Experiment show:Using this hybrid system,the independent existence of ATChand AChE,Acetic acid, as well as metal ions such as Cu2+and Hg2+exhibited littleinfluence on the fluorescence intensity of the Au QDs even could beneglected;however,different concentration of ATCh could effect on the inhibitionratio of AChE，which achieve the highest inhibition ratio in2.67mM.In addition,thedetection limit of the proposed biosensor is as low as2.18×10-4ppm;and indicatesselectivity that when detect on diverse species of OPs the results showdifferent.Finally,practical application of the Au QDs-AChE system has beendemonstrated by fruits and soil analysis.Results of paraoxon residues detection werein good agreement with those from gas chromatography in combination with mass spectrometry method.This complex system based on the coupling of efficientquenching of Au QDs fluorescence by thiocholine generated from AChE-catalyzedreaction and the effective enzymatic inhibition was proved to be a sensitive, rapid,simple method for detecting paraoxon pesticides. |
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