Study On The Novel Electrochemical Biosensors Based On Nanomateirals

Nucleic acid is significant biomacromolecule.Deoxyribonucleic acid(DNA) is the carrier of hereditary material.The sequence of these bases determines hereditary information.Thus,detecting DNA sequence is the key to uncover heredity code.The detection of specific DNA sequence in human body,viral and bacteria nucleic acid is playing more and more important role in many fields,such as Disease diagnosis, Foodstuff pollution,Legal medical examination,Environment survey.Proteins are fundamental materials of human body,involved in each reaction and maintain life activities.Protein Study has been receiving people's attention.The analysis of protein quantities is a vital part in chemistry,biochemistry and medicine.With the development of biotechnology,people focus on the study of gene and protein biology function,thus bring new subjects of functional genomics and proteomics.Electrochemical biosensor is a novel and developing technique that combining electrochemical and microelectronic techniques with the advantages of being simple,reliable,portable,minimal power,high sensitive and selective,and has been a hot topic in the field of biochemistry and medicine.Nanometer material,regarded as the most promising material of the 21th century, is a hotspot in material fields.Nanoparticles,with these unique physical and chemical properties,are providing new methods for biomedicine.The dissertation has developed novel and sensitive electronchemistry biosensor to detect nucleic acid and protein.Our proposal and experiment,based on excellent characteristics of nanoparticles,combining layer-by-layer technology and eletrochemical analysis technique,have made new attempt on the study ofbiosensor. This dissertation includes four chapters:Chapter 1:IntroductionFirstly,we reviewed the basic principle of biosensor,its classification,together with the application and development.Among these,we mainly mentioned DNA electrochemical biosensor and aptamer biosensor.Secondly,we referred to the application of nano-materials on the biosensor.Finally,we emphatically pointed out the purpose and significance of the dissertation,its innovation spot and content as well.Chapter 2:Multilayer membranes via layer-by-Layer deposition of PDDA and DNA with Au nanoparticles as tags for DNA biosensingA novel Au nanoparticles(Au-NPs)-based protocol for DNA hybridization detection based on assembly of alternating DNA and poly(dimethyldiallylammonium chloride)(PDDA) multilayer films by layer-by-layer(LBL) electrostatic adsorption has been studied.Electrochemical impedance spectroscopy(EIS) and UV-vis absorbance measurements were used to study the film assembly.The result indicated the multiplayer film can be assembled on the PPy modified electrode.The DNA biosensor has good sensitivity and reproducibility.Chapter 3:A new amplification strategy for electrochemical DNA biosensor based on the network structure formed by probes and target DNAWe have successfully amplified the target through network enriching the redox indicator,MB.MB can interact specifically with the guanine bases on the probes.The network was formed by Au nanoparticles modified probes and target.Thiocyanuric acid,a star-like molecular,can form network-like structure with gold nanoparticles due to its three mercapto.At the same time,Au-NPs/analyte aggregation can help electron transfer,making the Redox reaction more easily.So,this biosensor had high sensitivity to target.Chapter 4:An amplified electroehemical aptasensor for thrombin based on the network structure formed by probes and targetWe report here a biosensor to detect thrombin by two functional aptamer segments.Incubation for thrombin not only result in the binding multi-Au-NPs labeled probe to the analyte for formation of an extended polymeric network,but also in aggregation abundant MB molecules on the aptamer segments.The novel apatmer-based biosensing capability is coupled to the enormous amplification feature of the activation for MB through the Au-NPs conductive matrix to yield remarkably low(fmole) detection limits.