Electrochemical Sensors For Cardiac Troponin I Developed Using MOFs As The Signal Resource Or Signal Molecules Loading Platform

Metal-organic frameworks（MOFs）are porous metal-organic hybrid materials with unique structures and properties,which have the advantages of large specific surface area,high porosity and loading efficiency,easy functionalization,tunable pore size,better biocompatibility and biodegradability.Based on these advantages,MOFs have attracted much attention as electrochemical sensing interfaces and signaling molecules in electrochemical sensors.Cardiovascular disease is a serious threat to human health,and cardiac troponin I（cTnI）is considered to be the gold standard for diagnosing myocardial injury.Therefore,the construction of a simple,rapid and sensitive cTnI electrochemical sensor has important practical applications in the early diagnosis,development and prognosis of myocardial injury diseases.In this thesis,three MOF materials,copper-tannic acid（Cu-TA）,zirconium-based MOF（Ui O-66）,NH₂-MIL-53（Fe）/dopamine（DA）were fabricated by metal ion dissolution combined with electrochemical deposition,liquid phase epitaxy growth,and hydrothermal methods,respectively,and three easy-to-prepare and highly sensitive electrochemical sensors for the detection of cardiac marker cTnI,which enriched the detection method of cTnI.The main research works are as follows:（1）Copper-tannin acid（Cu-TA）metal-organic hybrid material with redox activity was synthesized in situ on the surface of glassy carbon electrodes by metal ion solubilization combined with electrochemical deposition strategy,and then catechol groups in TA were used to reduce chloroauric acid（HAu Cl₄）to gold nanoparticles（Au NPs）in situ at Cu-TA.Further,cTnI antibody molecules（anti-cTnI）were assembled on Au NPs as immobilized carriers to construct a novel cTnI sensing interface.Electrochemical experiments showed that the sensing interface showed that the sensing interface showed a good redox peak corresponding to Cu^2+/+in Cu-TA,and when the sensing interface anti-cTnI formed a complex with the target cTnI by immunoreaction,the thickening of the non-conductive molecular film formed an ionic barrier layer hindering the diffusion of electrolyte ions on the electrode surface,which in turn led to a decrease in the electrochemical activity of Cu-TA,thus allowing The label-free detection of cTnI was achieved.The results of quantitative analysis showed that the current response signal of Cu-TA in the sensor showed good linearity with the negative logarithm of the target concentration（10 fg/m L～10 ng/m L）under the optimal conditions,and the detection limit was0.65 fg/m L.Meanwhile,the results showed that the sensor exhibited good selectivity,and the recoveries of cTnI detection in actual serum samples were 98.3%～102%.（2）A layer of p-mercaptobenzoic acid（p-MBA）was self-assembled on the surface of bare gold electrode（Au E）through gold-sulfur bonding,followed by liquid-phase epitaxial growth method to immobilize zirconium ions(Zr⁴⁺)on the electrode surface by coordination,and then zirconium-based MOFs were prepared on-site on the electrode surface using the coordination of Zr⁴⁺with carboxyl groups（-COOH）in p-terephthalic acid（PTA）（Ui O-66）.The morphology and structure of Ui O-66 prepared by liquid phase epitaxy were characterized by scanning electron microscopy,infrared spectroscopy,X-ray diffraction and X-ray photoelectron spectroscopy.A novel sensing interface was further constructed by self-assembling the 5’-PO₄^3-modified cTnI nucleic acid aptamer onto the Ui O-66 surface using the strong coordination interaction between phosphate groups and Zr⁴⁺.Electrochemical experiments showed that Ui O-66 has catalase catalytic properties and can catalyze the reduction of H₂O₂,while when the aptamer interacts with cTnI to form a complex,the catalytic response of Ui O-66 to H₂O₂ is inhibited by the site-block barrier effect,which can be used for the recognition and detection of cTnI.The catalytic current of the sensor showed a good linear relationship with the negative logarithm of the target concentration in the range of 100 fg/m L～100 ng/m L,and the detection limit was 13 fg/m L.The sensor has good selectivity for cTnI and can be used for the detection of cTnI in human serum samples.（3）The NH₂-MIL-53（Fe）MOF material was prepared by hydrothermal method,and then the electroactive NH₂-MIL-53（Fe）/DA complex was synthesized by using the amidation condensation of the carboxyl group（-COOH）in the ligand 2-aminoterephthalic acid with the amino group（-NH₂）on dopamine（DA）;further,the cTnI nucleic acid aptamer containing 5’-PO₄^3-was further modified to NH₂-MIL-53（Fe）/DA surface by ligand interaction to obtain electrochemically active cTnI recognition materials.Meanwhile,gold nanoparticles（Au NPs）were electrochemically prepared on the surface of glassy carbon electrode,and then immobilized with cTnI antibody molecules.After the cTnI antibody has adsorbed the cTnI molecule on the electrode surface by immunoreactivity,the NH₂-MIL-53（Fe）/DA material can be further chemisorbed by the aptamer to obtain the signal-on electrochemical response corresponding to DA.The sensitive detection of cTnI can be achieved by this heterogeneous sandwich structure.The analytical results showed a good linear relationship between the signal intensity and the negative logarithm of cTnI concentration in the range of 10 fg/m L～100 ng/m L,with a detection limit of 0.92 fg/m L.The good selectivity of this sensor provides a feasible technique for the detection of cTnI in human serum.