Construction And Application Of Electrochemical Sensing Based On Carbon Nanomaterials And Nucleic Acid Aptamers

Biosensor is a multidisciplinary research filed involved biology,physics,chemistry,materials and electronics.The electrochemical methods have many advantages,such as high sensitivy,simple design,rapid respnse,low cost,miniaturization of the instruments,portable and so on.Due to their excellent optical,electrical and mechanical properties and biocompatibility,carbon based nanomaterials play an important role in the research field of biosensors.The aptamer has a number of advantages such as high specificity,affinity,low cost,easier modification and functionalization and so on,it would be widely reached and used in biology,chemistry,medical and material science.Therefore,according to the excellent properties of carbon based nanomaterials and aptamers of nucleic acid,this thesis combines carbon based nanomaterials,nucleic acid aptamers and electrochemical sensors,and carries out the following main work:1.A sensitive and selective electrochemical sensor based on carboxyl graphene(CG),polypyrrole(PPy),and chitosan(CS)nanocomposite-modified glassy carbon electrode(GCE)has been developed for nitrite determination.The electrochemical performances of CG/PPy/CS/GCE were characterized by cyclic voltammetry and electrochemical impedance spectroscopy.Under the optimum experimental conditions,a linear relationship between DPV peak current and the concentration of nitrite was obtained in the range of 0.2 to 1000 μM.The limit of detection of nitrite was estimated to be 0.02 μM.Using such modified electrodes,our method is quite reproducible for nitrite determination,even for real water samples.2.The sodium oleate was used to synthesis of gold nanorods by layer assisted method.Titration method was prepared by GNRs/CS/NH2-r GO/GCE.We uses cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS),chronocoulometry to characterize the materials in the surface of electrodes.The electrochemical behavior of tyrosine on the surface of GNRs/CS/NH2-r GO/GCE was studied by differential pulse voltammetry(DPV).The experimental conditions were optimized.Under the optimal conditions,the DPV determination of tyrosine on GNRs/CS/NH2-r GO/GCE was carried out.he linear range of tyrosine was 0.02-50?M and the detection limit was 6.04 ?M.3.A highly selective method for the electrochemical detection of reduced glutathione(GSH)has been developed on the basis of the product of a reaction between GSH and catechol as the electron mediator on amino-functionalized graphene quantum dots modified glassy carbon electrode.The best indicator was selected by comparing experiments,and the experimental conditions were optimized.Under the optimal experimental conditions,when the concentration of GSH in 1-130 ?M range of concentration,it shows a good linear relationship with a detection limit of 0.1 ? M GSH.In addition,we have adopted this approach to determination of real samples,it obtained the satisfactory results.4.An electrochemical method for the determination of the single-stranded DNA(ss DNA)oligonucleotide with a sequence derived from the genom of hepatitis B virus(HBV)was described.It is making use of circular strand displacement(CSD)and rolling circle amplification(RCA)strategies mediated by a molecular beacon(MB).This ss DNA hybridizes with the loop portion of the MB immobilized on the surface of a gold electrode,while primer DNA also hybridizes with the rest of partial DNA sequences of MB.This triggers the MB-mediated CSD.The RCA is then initiated to produce a long DNA strand with multiple tandem-repeat sequences,and this results in a significant increase of the differential pulse voltammetric response of the electrochemical probe Methylene Blue.Under optimal experimental conditions,the assay displays an ultrahigh sensitivity.Response is linear in the 10 to 700 a M DNA concentration range.The limit of determination is 2.6 a M.