The Investigation Of Au And Ag Nanomaterials In New-type Electrochemical Biosensor Technology

Electrochemical immunosensors are considered to be effective methods for quantitative detection of biomolecules because of the advantages of simplicity,speed,high sensitivity,acceptable selectivity and low cost.The research and application of nanomaterials are an important part of the development of immunosensor technology.Due to large specific surface area,stable chemical properties,excellent conductivity,good biocompatibility and other special properties,gold and silver nanoparticles are widely used in the immunosensor field.This thesis mainly includes the following four parts:In the first section,a dual-mode competitive electrochemical immunosensor for sensitive detection of B-type natriuretic peptide（BNP）was successfully fabricated,which based on differential pulse voltammetry（DPV）and amperometric i-t（i-t）curve response modes.Polyaniline（PAN）and tin dioxide（SnO₂）were loaded on graphene sheets（GS）,which could effectively promote the electron transfer process,thereby amplifying the current signal and increasing the sensitivity of the immunosensor.To promote biocompatibility,gold nanoparticles（Au）were incorporated on GS/SnO₂/PAN.GS/SnO₂/PAN/Au complex was gotten to act as the platform which could provide a clearly DPV signals.N-doped carbon nanotubes（N-CNTs）embellished by ZnCo₂O₄ quantum dots（ZnCo₂O₄/N-CNTs）with excellent catalytic properties for the reduction of H₂O₂ was gotten to act as the label of the antibody-BNP（Ab）,providing an obviously current signal through i-t curve method.A large quantity of BNP could be stable loaded in the modified electrode via GS/SnO₂/PAN/Au,which could compete with target-BNP to combine Ab that labelled by ZnCo₂O₄/N-CNTs.Under the optimum conditions,the immunosensor exhibited remarkable analytical performance of a linear range from 0.01 pg/mL to 1ng/mL with a detection limit of 3.4 fg/mL for quantitative detection of BNP（S/N=3）.This method was able to become a novel approach for other biological detection.In the second section,an ultrasensitive competitive electrochemical immunosensor about quantitative detecting diethylstilbestrol（DES）was constructed by linear sweep voltammetry（LSV）.In this work,Cu₃（BTC）₂ loaded with silver nanoparticles（Ag NPs）was served as matrix,which causes an strong electrochemical signal of Ag/Ag⁺for the detection of DES.Nevertheless,the signal was reduced in virtue of antibodies and antigens with depress the electron transfer and obstruct signal transmission.To further decrease of the electrochemical signal and magnify signal changes,amino functionalized hematite（α-Fe₂O₃-NH₂）,an n-type semiconductor with large steric hindrance,was served as the marker.In devised immunosensor,DES can compete with the bovine serum albumin-diethylstilbestrol markedα-Fe₂O₃-NH₂（α-Fe₂O₃-BSA-DES）to combine specific sites of antibody.Owing to small molecular weight of DES,it was easier to combine antibodies thanα-Fe₂O₃-BSA-DES.Therefore,the current signal will augment as the increase of DES concentration.This immunosensor offered outstanding analytical performance about quantitative detection for DES with a broad range from 0.005 to 500 ng/mL and a low detection limit about 1.67 pg/m L（S/N=3）.In the third section,a ratiometric electrochemical immunosensor was manufactured to quantitative detection of procalcitonin（PCT）by DPV.Graphitic carbon nitride（g-C₃N₄）with high chemical stability and good biocompatibility was a feasible support material to carry Ag NPs which could own an obvious oxidative peak.The doping of Ag NPs into g-C₃N₄（g-C₃N₄-Ag NPs）was not only beneficial to prevent the agglomeration of Ag NPs,but also favorable to improve the electron transfer velocity of g-C₃N₄.Moreover,the g-C₃N₄-Ag NPs as the matrix could immobilize primary antibody by Ag-NH₂ bond.Nile blue A（NBA）which could offer a current signal at-0.38V was an excellent redox probe based on the redox reaction with one-electron two-electron.Due to large surface area and high porosity,Zr-based metal organic framework-UiO-67 was an ideal framework material,which could absorb the substantial NBA by electrostatic adsorption.In the meantime,UiO-67bearing NBA（NBA-Ui O-67）owned admirable biocompatibility was a qualifying marker to load the secondary antibody.For the immunosensor,the current ratio of NBA to Ag NPs(I_NBA/I_{Ag NPs})was increased as the concentrations of PCT rose.Under the optimal conditions,the immunosensor displayed preeminent analytical performance with a linear range from 0.005 to 50 ng/m L and a detection limit of 1.67pg/mL（S/N=3）.This proposed immunosensor strategy,a straightforward and reliable platform,affords a great potential application in biometric analysis.In the fourth section,a dual-mode label-free electrochemical immunosensor was constructed by DPV and i-t for sensitive detection of PCT.NiCo₂S₄ was an excellent electrocatalyst with high chemical activity in catalyzing H₂O₂.NiCo₂S₄ was loaded on g-C₃N₄ that not only facilitated the activation of bimetal activity,but also effectively prevented the aggregation of NiCo₂S₄.To increase the conductivity of the material,CNTs was loaded into the material.To further enhance the catalytic properties of the composites,Ag NPs was combined with NiCo₂S₄-g-C₃N₄-CNTs.The signal strength was amplified by the composite of the material.In addition,Ag/Ag⁺signal was detected by DPV to realize sensitive detection of PCT.Under the optimum conditions,the detection range of the immunosensor was 0.05 ng/ml-50 ng/m L（DPV）and 1pg/ml-10 ng/mL（i-t）,and the detection limit was 16.7 pg/mL（DPV）and 0.33 pg/m L（i-t）,which has good selectivity and practical application value.