Studies Of DNA Biosensor Based On MOF Materials

Metal organic framework materials（MOFs）,due to their customizable structure and function,high porosity and large specific surface area,have attracted widespread attention.However,few MOFs have been explored for the biosensor because of their poor conductivity and water solubility.Two-dimensional（2D）MOF nanosheets,due to their high aspect ratios,ideal ultrathin thickness and good electrochemical activity,are more suitable for construction of DNA biosensor.In this work,three kinds of DNA biosensors for ultrasensitive detection of tumor markers miRNA and marine pathogenic bacteria were developed based on Ru-MOF nanosheets.The detail contents were described as follows:1.Ruthenium-based metal organic framework（Ru-MOF）-derived novel Faraday-cage electrochemiluminescence biosensor for ultrasensitive detection of miRNA-141A novel Faraday-cage electrochemiluminescence（ECL）biosensor for the sensitive detection of miRNA-141 was constructed.The capture unit was prepared by immobilizing the capture DNA（cDNA）on the functionalized magnetic nanospheres Fe3O4@SiO2@Au,while the signal unit was ruthenium-based metal organic framework Ru-MOF labeled by signal DNA（sDNA）.The recognition scaffold was as follows:the capture unit was immobilized onto the magnetic electrode surface;the target miRNA-141 was caught;the signal unit was further hybridized;the Faraday-cage biosensor structure was formed finally.In this case,the signal unit became part of the electrode surface,the outer Helmholtz plane（OHP）of the proposed electrode was extended,all electrochemiluminophores in the signal unit could take part in the electrode reaction,and thus then the detection sensitivity was greatly improved.Taking advantage of the proposed Faraday-cage cascade,the ECL intensity was found to increase with the logarithm of miRNA-141 concentration.The linear range was wide from 1 fM to 10 pM with a limit of detection 0.3 fM.The selectivity,stability,reproducibility,precision and application of this biosensor were validated.This proposed Faraday-cage ECL biosensor has a potential prospect for clinical miRNA detection.2.Potential-resolved Faraday cage-type electrochemiluminescence biosensor for simultaneous determination of miRNAs using functionalized g-C₃N₄ and metal organic framework nanosheetsHere,a novel Faraday cage-type electrochemiluminescence（ECL）biosensor was presented for simultaneous determination of miRNA-141 and miRNA-21 based on the potential-resolved strategy.In this work,capture units were prepared by immobilizing hairpin DNA1（HP1）and hairpin DNA2（HP2）on Fe3O4@Au nanocomposites,while g-C3N4@AuNPs nanocomposites labelled by signal DNA1（sDNA1）and ruthenium-based metal organic framework（Ru-MOF）nanosheets labelled by signal DNA2（sDNA2）were used as signal units.In this proposed biosensor,signal units g-C3N4@AuNPs-sDNA1 and Ru-MOF-sDNA2 could exhibit two strong and stable ECL emissions at-1.4 V and+1.5 V respectively,which could be used as effective potential-resolved signal tags.Moreover,taking advantage of the proposed Faraday cage-type model,all electrochemiluminophores in the signal units could take part in electrode reactions,the signal units became part of the electrode surface and extended the outer Helmholtz plane（OHP）of the proposed electrode,and then the detection sensitivity was improved greatly.Accordingly,dual targets miRNA-141 and miRNA-21 could be detected within the linear range of 1 fM to 10 pM,with the detection limit of 0.3 fM.Meanwhile,the proposed miRNA assay exhibited high selectivity and sensitivity,even for practical analysis in human serum.So,this potential-resolved ECL biosensor is proved to be a feasible tool for dual targets detection of miRNAs in clinical diagnosis.3.Dual-modal Faraday cage-type aptasensor based on electrochemiluminescence and differential pulse voltammetry for ultrasensitive detection of Vibrio ParahemolyticusA simple and efficient dual-modal Faraday cage-type aptasensor was developed for ultrasensitive detection of Vibrio Parahemolyticus（VP）based on electrochemiluminescence（ECL）and differential pulse voltammetry（DPV）.The signal unit was ruthenium-based Ru-MOF@Pb²⁺labeled by aptamer 2（Apt 2）.After being captured by aptamer 1（Apt 1）on gold electrodes,VP was recognized by signal unit,achieving ECL and DPV dual-modal detection.Compared with traditional sandwich-type immunosensors,this proposed aptasensor has the advantages of significant signal amplification effects,due to its distinctive Faraday cage-type structure.The selectivity,stability and reproducibility of this aptasensor were satisfactory.In addition,the results of two detection methods can mutually validate each other to avoid false positive results.Moreover,this Faraday cage-type aptasensor with dual-modal detection can also be used for detection of VP in seawater sample,which would be a promising tool for pathogenic bacteria analysis.