Study On Electrochemical Biosensor Based On Signal Amplification Strategy Of Nanomaterials With Enzymatic Function

Electrochemical biosensors hold the advantages of fast response,easy operation,low cost,high sensitivity,which attracted much attention in the field of analysis.In recent years,in order to futher improve its analytical performance,various multifunctional nanomaterials were used to construct electrochemical biosensors.We mainly studied the novel nanomaterials with catalytic function and its application in electrochemical biosensors preparation.The details are mainly as follows:1.Three-dimensional nano-network composed of Pt nanoparticles functionalized Mn-doped CeO₂ and hemin/G-quadruplex as electrocatalysts for the construction of electrochemical biosensorWe prepared platinum nanoparticles functionalized Mn-doped CeO₂?Pt@Mn-CeO₂NPs?and G-riched DNA sequences were subsequently modified on their surface.Furthermore,a novel three-dimensional nano-network was developed as electrocatalyst and biolabels based on the partly hybridization of DNA sequences on Pt@Mn-CeO₂NPs,which enabled highly sensitive detection of biomarker of cardiactroponin I?cTnI?.It was worth pointing out that?1?the G-rich sequences on three-dimensional nano-network of Pt@Mn-CeO₂ NPs could embed masses of hemin as redox mediator and electrocatalysts;?2?the formation of the new synergistic pseudobienzyme-catalyzed cascade system based on hemin/G-quadruplex and Pt@Mn-CeO₂ NPs could amplify the electrochemical signal in the presence of the L-cysteine,which was the electrocatalytic substance.And on the basis of this strategy,the immunosensor showed a wide linear range from 0.5 pg mL^-11 to 100 ng mL^-11 and a low detection limit of 0.15 pg mL^-1.2.Platinum nanoparticle functionalized copper-incorporated covalent organic frameworks to construct ratiometric biosensorsPlatinumnanoparticlefunctionalizedcopper-incorporatedcovalentorganic frameworks?Pt/Cu-COF?were prepared and used as signal units to develop a novel,simple ratiometric electrochemical biosensor for the detection of miR-205.Covalent organic frameworks hold the merits of large specific surface area,strong conductivity,good catalytic property,and special functional groups.However,there was no reports on it as an electrochemical signal unit.We introduced copper into the covalent organic framework to synthesize the composite copper-incorporated COF?Cu-COF?,and further modified Cu-COF with platinum nanoparticle to obtain Pt/Cu-COF composite nanomaterials.Pt/Cu-COF composite nanomaterials have good film formation as a base material,and for the first time as an electrochemical signal unit for the construction of electrochemical biosensors.In addition,Pt/Cu-COF exhibited good catalytic performance for L-cysteine,which further improved the electrochemical signal.At the same time,ferrocene?Fc?was introduced as another signal unit,and the ratio of the peak current values of Fc and Cu-MOFs was calculated.The linear range of the ratiometric sensor was 0.1 pmol L^-11 to 20 nmol L^-11 and the detection limit was 0.1 pmol L^-1,which demonstrated high accuracy and high sensitivity.3.AnEfficientElectrochemicalSelf-Catalyticplatformbasedon L-Cys-hemin/G-quadruplex and Its Application for BioassayCommonly,in the artificial enzyme-assisted signal amplification strategy,the catalytic efficiency was limited by the relatively low binding affinity between enzyme and catalytic substrate.In this work,substrate L-cysteine?L-Cys?and hemin were combined into a molecule to form L-Cys-hemin/G-quadruplex as artificial self-catalytic complex.The apparent Michaelis-Menten constant(K_m=2.615?mol L^-1)on L-Cys-hemin/G-quadruplex for L-Cys was further investigated to assess the affinity,which was much lower than that of hemin/G-quadruplex(K_m=8.640?mol L^-1),confirming L-Cys-hemin/G-quadruplex possessed better affinity to L-Cys compared with that of hemin/G-quadruplex.Simultaneously,L-Cys bilayer could be further assembled onto the surface of L-Cys-hemin/G-quadruplex based on hydrogen-bond and electrostatic interaction to concentrate L-Cys around the active center,which was beneficial to the catalytic enhancement.Through this design,the aptasensor exhibited good sensitivity from 0.1 pmol L^-11 to 80 nmol L^-11 with a detection limit of 0.03 pmol L^-1.