Construction Of Electrochemical Aptasensor Based On Nanomaterials Signal Amplification Methods

With the development of the society and people's higher demand for health,it is highly desirable to develop a simple,fast,highly selective and sensitive method for food safety analysis.In this thesis,we used aptamers as target recognition elements,combined with a variety of signal amplification methods based on nanomaterials,realized the sensitive detection of heavy metal ions and biotoxins in food.This provided a new direction for food safety detection.There are four chapters in this thesis.The main contents are listed as follows:In chapter 1,we provided a brief overview of the advance and trend on aptamer and electrochemical aptasensors.And then the application of new nanomaterials in the electrochemical aptasensors,especially,a series of novel signal amplification strategies based on nanomaterials were introduced.In addition,the research ideas and contents of this thesis were summarized at last.In chapter 2,a new electrochemical aptasensor has been developed for highly sensitive detection of Okadaic Acid(OA)based on silver-enhanced gold nanoparticle label.The binding of OA to the aptamer immobilized on the electrode surface induced the unwinding of dsDNA,which would produce free ssDNA for the followed hybridizing with AuNPs labeled probe DNA.The electrochemical signal was finally obtained by the direct electrochemical oxidation of the silver nanoparticles on the surface of AuNPs.The detection of OA was achieved with a linear range from 10.0 pg/mL to 500.0 ng/mL and a detection limit of 8.8 pg/mL.This sensor is simple,sensitive and has a wide detection range.In chapter 3,graphene oxide(GO)catalyzed silver nanoparticles deposition is newly designed as trace tag for electrochemical lead ions biosensor based on the different binding ability of GO to single and double stranded DNA and its characteristics of catalytic reduction of silver ions.In the presence of weak reductant,GO catalyzed silver ions into silver nanoparticles.Through direct electrochemical oxidation of the silver nanoparticles on the surface of GO to obtain the,electrochemical signal,an ultrasensitive electrochemical method for lead ions detection was developed.Under optimal conditions,this method showed a wide linear range from 0.1 nM to 10.0 ?M with a detection limit of 0.084 nM.This ultrasensitive sensor was also successfully applied to the determination of Pb2+ in river samples,and the results showed good correlation with those obtained by ICP-MS.In chapter 4,based on the efficient catalytic property of DNA-templated copper nanoparticles toward H2O2 reduction,a sensitive,simple,sensitive "turn-off" OTA biosensing strategy was firstly proposed.UV-vis and fluorescence spectra were used to characterize the CuNPs.Under optimal conditions,because of high catalytic capability of CuNPs in response to H2O2 reduction,the detection of OTA with this signal-amplified electrochemical aptasensor achieved an extraordinary LOD of 0.87 pg/mL.The obtained linear range was between 1.0 and 250.0 pg/mL.At last,the electrochemical aptasensor was successfully applied to the determination of OTA in red wine sample.