Fabrication Of Metal-organic Hybrid Material Modified Interface And Electrochemical Sensing Application

Metal-organic hybrid materials are widely used in the electrochemical field because of their high porosity,large specific surface area,and their own electrical activity.Traditional electrochemical nucleic acid sensors usually need to label exogenous signal molecules,and obtain sensing signals through the redox response changes of these molecules,thereby indirectly measuring target molecules.However,these methods have shortcomings such as cumbersome process and high price,and they are easily affected by external environmental factors,resulting in poor stability.Therefore,this paper uses cyclic voltammetry and other electrochemical methods combined with in-situ growth to modify the electrochemically or electrocatalytically active copper/phytic acid（PA）,Prussian blue（PB）/polydopamine（PDA）on the surface of the glassy carbon electrode.MIL-88NH₂（Fe）and other metal-organic hybrid materials.Three simple,economical and sensitive laber-free electrochemical biosensors were constructed and used for the detection of target molecules,and a new labeling free sensing strategy was constructed.The main research work are as follows:（1）Using cyclic voltammetry to deposit copper on the glassy carbon electrode（GCE）,and then drip phytic acid（PA）,using the acidity and strong complexing ability of phytic acid to form a PA-Cu composite modified electrode（PA-Cu/GCE）);Then use the electrodeposition method to deposit gold nanoparticles（AuNPs）on the surface of PA-Cu/GCE,and then use the Au-S bond to self-assemble the probe DNA（pro-DNA）on the surface of the modified electrode,constructing a new type of electrode Chemical sensor（pro-DNA/AuNPs/PA-Cu/GCE）.The electrode preparation process was characterized by physical means such as scanning electron microscope and Fourier transform infrared spectrometer.The results show that the granular AuNPs/PA-Cu composite material effectively adheres to the electrode surface.Electrochemical experiments show that AuNPs/PA-Cu has high-efficiency electrocatalytic activity for H₂O₂,and the biohybridization reaction on the electrode surface can significantly inhibit the catalytic activity.Based on this,the sensor is applied to the detection of target mi RNA-let 7a.The results showed that in the detection range of 1.0 f M～10 n M,the timing catalytic current corresponds to a good linear relationship with the negative logarithm of the concentration of mi RNA-let 7a,and the detection limit is 0.4 f M.Then the reproducibility and selectivity of the sensor were investigated,and the results were satisfactory.In addition,the constructed sensor has good detection results for actual serum samples,with a recovery rate of 98.3%～103%.The sensor is expected to be applied in actual sample detection.（2）Electrodeposition was used to modify the electroactive Prussian blue（PB）on the surface of the glassy carbon electrode,and then auto-polymerize on the surface of the modified electrode to form polydopamine（PDA）and adsorb Ce³⁺.Further through the coordination of Ce³⁺with the phosphate backbone of DNA,the probe DNA（pro-DNA）was modified to design a new type of electrochemical biosensor.Scanning electron microscopy,Fourier transform infrared spectrometer and other physical characterization results show that PDA@PB is regular granular,and the sensing interface has good hydrophilicity.The electrochemical redox peak current of PB on the electrode surface was used as the sensing signal for mi RNA-let 7a label-free detection.The results showed that the peak current difference and the target concentration logarithm showed a good linear relationship in the range of 0.1 f M～10 n M,The detection limit reached 0.03 f M.In addition,because of the good self-cleaning performance of the PDA membrane,the sensor exhibits excellent anti-pollution performance and can be used for the effective detection of mi RNA-let 7a in serum samples.（3）A metal-organic framework（MOF）material with mimic enzyme electrocatalytic activity,MIL-88NH₂（Fe）,was synthesized by hydrothermal method.Then it was fixed on the surface of the carboxylated glassy carbon electrode by covalent bonding.Furthermore,through the specific coordination between the phosphate group and Fe（III）,the 5’-PO₄^3-modified chloramphenicol（CAP）aptamer was self-assembled on the electrode surface,and a novel electrochemical sensing interface was constructed.The modification process was characterized by atomic force microscopy（AFM）.Taking the change of the catalytic activity of the MIL-88NH₂（Fe）nanozyme on hydrogen peroxide and 3,3’,5,5’-tetramethylbenzidine（TMB）system as an indicator signal,the analytical performance of the sensor was investigate.The results showed that after the nucleic acid aptamer and CAP interacted on the electrode surface,the steric hindrance of the electrode surface and the change of the environment would inhibit the catalytic activity of MIL-88NH₂（Fe）on the substrate.Quantitative analysis showed that CAP was in the concentration range of 1.0 p M～1.0μM,and the change in catalytic current had a good linear relationship with the logarithm of CAP concentration,and the detection limit was as low as 330 f M.The sensor can be applied to the detection of CAP in milk samples.