Research On The Construction Of Ratio Electrochemical Aptamer Sensor Based On Metal Organic Framework Nanocomposite And Its Biochemical Analysis

Low-dimensional nanomaterials have numerous merits,such as largely specific surface areas,highly catalytic performances,easy to modify the surface with different functional groups.Among them,the large surface area can effectively immobilize biomolecules on the surface of electrodes,therefore improving the sensitivity of the electrochemical sensors.At the same time,low-dimensional nanomaterials can improve the electron transfer rate on the electrode surface.Thus,in electrochemical sensors,low-dimensional nanomaterials can be used to amplify the electrochemical signal responses.Metal organic frameworks?MOF?as one of functional materials with a wide range of uses,have many advantages,such as largely specific surface area,high porosity,the ordered crystal structure,excellent mechanical stability,and so forth.The effective combination of MOF with other nanomaterials can make up for the shortcomings of a single component,so that MOF composite materials have a more extensive application prospect in the field of electrochemical sensors.In this paper,according to the preparation strategies and applications of electrochemical aptamer sensors,the method of preparing new nanocomposites with MOF and other nanomaterials was studied.Novel ratiometric electrochemical sensors were constructed for highly selective and sensitive detection of vanillin and mi R3123.One:In this work,a facile ratiometric electrochemical aptasensor was developed towards sensitive and selective detection of vanillin,based on Ketjen black/ferrocene dual-doped zeolite-like MOFs?Fc-KB/ZIF-8?and the electro-deposited gold nanoparticles?AuNPs?coupling with DNA aptamer.Fc-KB/ZIF-8 composites were prepared via one-pot solvothermal reaction and drop-coated on glassy carbon electrode?GCE?surface to form Fc-KB/ZIF-8@GCE.AuNPs were in-situ electro-deposited on the modified GCE.The 5'-SH terminated aptamer of vanillin was combined with AuNPs via Au-S coupling to form aptamer-AuNPs/Fc-KB/ZIF-8@GCE as a new sensing platform.Under the optimal conditions,electrochemical?square wave voltammetry?curves of this sensing platform were measured in electrolyte solutions containing vanillin.With the increase of vanillin concentration(C_van),vanillin had an increased peak current intensity(I_van,as the response signal).Fc doped into ZIF-8 had slight changes in its peak current intensity(I_Fc,as the reference signal).There is a well plotting linear relationship between I_van/I_Fc and the logarithm of Cvan ranging from 10 nM to 0.2 mM,with a low limit of detection of 3 nM.The Aptamer-AuNPs/Fc-KB/ZIF-8@GCE was applied as a ratiometric electrochemical aptasensor of vanillin.This aptasensor had sensitive and selective electrochemical signal responses on vanillin,over potential interferents.This aptasensor enabled vanillin detection in real food samples,showing high detection performance.Experimental results testified that this aptasensor had high reliability and practicability for vanillin determination in real samples.Two:Novel two-dimensional?2D?metal-organic frameworks?MOF?were one-pot prepared by solvothermal reaction,by using copper nitrate and 4,4',4'',4'''-?porphine-5,10,15,20-tetrayl?tetrakis benzoic acid as precursors and thionine?TH?as the doping component.Black phosphorus nanosheets?BPNSs?were prepared by liquid-phase exfoliation of bulk crystals and were adhered to TH-doped 2D MOF?TH/Cu-MOF?to produce BPNSs/TH/Cu-MOF complex.The complex was drop-casted on glassy carbon electrode?GCE?to construct BPNSs/TH/Cu-MOF/GCE,followed by combining ferrocene?Fc?-labeled single-strand DNA aptamer to form Aptamer-BPNSs/TH/Cu-MOF nanohybrid on GCE.The formation process of nanohybrid was characterized and experiment conditions were optimized.Under optimal conditions,the Aptamer-BPNSs/TH/Cu-MOF/GCE platform served as a smart ratiometric electrochemical aptasensor that can accurately capture and detect microRNA?miR3123?.With increase of miR3123 concentration(C_miR3123),the redox peak current of Fc(I_Fc)decreased,because special combination of Fc-Aptamer with miR3123 led to Fc away from GCE surface.TH was doped into 2D MOF and its peak current(I_TH)had negligible changes.TH and Fc acted as reference signal and response signal,respectively.There is a plotted linear relationship between(I_Fc/I_TH)and logarithm of C_miR3123 in the range from 2 pM to 2?M,together with a low limit of detection of 0.3 pM.The aptasensor had high sensitivity,selectivity and stability,and was applied to accurate detection of miR3123 in practical samples,showing high practicability.According to the functionalized MOF-based nanocomposites,novel ratiometric electrochemical aptamer sensors with high selectivity and high sensitivity were constructed by using the synergistic enhancement effects between MOF and noble metal nanoparticles or black phosphorus nanosheets.Based on MOF and other nanomaterials,novel functionalized nanocomposites were prepared and used as the electrode modification materials on GCE surface,which not only provided abundant active sites,but also enhanced the sensitive response of electrochemical signals.The ratiometric electrochemical aptamer sensors prepared in this paper have high selectivity and sensitivity during the biochemical analysis process of small biological molecules and nucleic acids.The as-prepared sensors have high recoveries in the practical sample detection containing the targets and demonstrate excellent detection performances.