Fabrication Of MOFs Derived Nanomaterials And Their Application In Electrochemical Biosensors

The abnormal expression of miRNA is not only related to tumor,but also different in different tumors.miRNA,as a part of cancer signaling pathway,has potential as a biomarker of tumor,which affects the diagnosis,treatment and prognosis of tumor.Compared with RNA sequencing,microarray and Northern blot,electrochemical biosensor is suitable for detecting miRNA with low abundance due to its high sensitivity,wide linear range,low limit of detection(LOD)and cost.Metal organic frameworks(MOFs)have important applications in gas storage,adsorption and release,catalysis,sensing and drug delivery due to their high porosity,large specific surface area,adjustable pore size and unsaturated metal active sites.However,the conductivity of pure MOFs is poor,so MOFs derived nanomaterials are widely used in the sensing field.Zeolitic imidazolate framework(ZIF),as a branch of MOFs,not only has the excellent characteristics of MOFs,but also has the porous and chemical stability of zeolite materials,which makes it more excellent in comprehensive performance.In this paper,the application of two different ZIF derivatives in electrochemical biosensor was studied,and microRNA-21(miRNA-21)in serum and tumor cells was quantitatively detected.By optimizing the electrodeposition time of Au Nanoparticles(Au NPs),the incubation time of microRNA(miRNA),the concentration the incubation time of signal probe,the sensor with excellent performance was finally constructed.Catalytic hairpin assembly(CHA)and hybrid chain reaction(HCR)were also used to improve the sensitivity of the sensor and reduce the LOD.Firstly,the precursor template ZIF-67 was synthesized under mild conditions,and the Co-CN material riching in N element and Co active sites was obtained by direct pyrolysis.Through miRNA-21 inducing CHA reaction,not only single strand DNA1(ss DAN1)trigger chain can be released,but also miRNA-21 can be recycled to start CHA reaction again and improve the utilization rate of miRNA-21.In this sensing platform,the released ss DNA1 can trigger the subsequent enzyme assisted cycle amplification,and achieve highly sensitive detection of miRNA-21 through the switch of methylene blue(MB)signal.The linear range of the sensor is10-50000 fmol L^-1,and the LOD is 4.67 fmol L^-1.Secondly,precursor ZIF-8 was synthesized by solution coprecipitation method at room temperature,and carbon nanomaterials riching in nitrogen(N-PCD)were prepared by calcination under N₂protection at high temperature.ZIF-8 and N-PCD were characterized by various methods.The results show that N-PCD not only retains the porous and high specific surface area characteristics of precursor ZIF-8,but also improves the electrical conductivity of the materials with uniform distribution of C and N elements.The synthesized tetrahedral DNA(T4-DNA)as a rigid scaffold can not only be stably fixed on the electrode surface,but also maintain the appropriate orientation,which is convenient for the recognition of miRNA-21 on the electrode surface,so as to amplify the signal.The results show that ferrocene(Fc)and MB can further amplify the response signal through HCR,and the dual signal readout system can help to obtain more accurate detection results.The LOD of Fc and MB is 1.92 fmol L^-1and 3.74 fmol L^-1,respectively,and the sensor constructed by this method can be used to sensitively detect miRNA-21 in cell samples.