Electrochemical Biosensing Properties Of Porphyrin-based Covalent-organic Framework Nanomaterials

Covalent-organic frameworks(COFs)are a class of organic porous covalent organic polymers constructed by covalent linkages.It is mainly composed of light elements(C,H,O,N,B,S,etc.)structural units connected by covalent chemical bonds to form a one-dimensional,two-dimensional or three-dimensional framework structure,the framework can be pre-designed.COFs Nanomaterials have the advantages of low density,large specific surface area,high chemical stability,and tunable structural pores,so they have potential applications in the fields of heterogeneous catalysis,gas adsorption and separation,energy storage,sensing and detection,and biomedicine..The basic properties of COFs materials depend on their building units.Among them,porphyrin-COFs(porphyrin-COFs,p-COFs)have high conjugated?-electron macrocyclic structure,high electrochemical activity,abundant The porosity and so on have received more and more attention in the fields of biomedicine and biosensing.In this thesis,porphyrin structural units with conjugated systems were selected to react with different monomers,and several imine-based p-COFs materials were designed and synthesized,which were used as sensing platforms to construct electrochemical biosensors,which were applied to antibiotics,Analysis and detection of bacteria and viruses.It mainly includes the following aspects:First,5,10,15,20-tetrakis(4-aminophenyl)porphyrin(TAPP)and 1,3,6,8-tetrakis(4-formylphenyl)pyrene(TFPy)were used as reaction monomers,a covalent organic framework(TAPP-TFPy-COF)linked by imine bonds was synthesized by solvothermal polycondensation and used as a platform to immobilize diethylstilbestrol(DES)-targeted DNA strands to prepare an electrochemical sensor for detecting DES.TAPP-TFPy-COF has high specific surface area,good electrochemical activity and high biological affinity for DES.The TAPP-TFPy-COF-based aptamer sensor showed excellent sensing performance for DES with a lower limit of detection(LOD)of 0.37 fg m L^-1in the concentration range of 1 fg m L^-1?1 ng m L^-1,a low compared to most of the DES sensors reported so far.Furthermore,the TAPP-TFPy-COF-based aptamer sensor showed good applicability to DES in real samples including frozen shrimp,milk,and Tap water.Second,a two-dimensional porphyrin-based covalent-organic framework(TAPP-DPDD-COF)was synthesized using TAPP and 2,2'-dipyridine-5,5'-dicarbaldehyde(DPDD)as reaction units.Then use it as a bifunctional platform to anchor the N-gene targeting aptamers or antibodies of SARS-Co V-2,respectively,to develop TAPP-DPDD-COF-based aptamer sensors and immunosensors for SARS-Co V-2 detection.Due to the coexistence of porphyrin and bipyridine groups in the synthesized TAPP-DDPD-COF,it has a strong binding effect on SARS-Co V-2 N-gene targeted aptamer chain and antibody.The developed TAPP-DDPD-COF based electrochemical adapter sensor and immune sensor can realize highly sensitive detection of SARS-Co V-2 N-gene.In the range of 0.1 fg m L^-1?1 ng m L^-1of N-gene,the LODs were 0.59 and 0.17 fg m L^-1,respectively,with good stability,excellent selectivity and regeneration.In addition,this work further explores the detection of TAPP-DPDD-COF-based electrochemical aptamer sensors and immunosensors in real samples,such as human serum,seawater,seafood,and throat swabs,etc.It is found that the theoretical value of the N-gene measured in real samples is in good agreement with the actual added value,which shows that both the TAPP-DPDD-COF-based aptamer sensor and the immunosensor can realize the accurate detection of SARS-Co V-2N-gene in a complex environment.Finally,TAPP and 2,2'-bithienyl-5,5'-dicarboxaldehyde(TDC)were synthesized into a two-dimensional TAPP-TDC-COF nanosheet structure and used as a platform to construct a sensor to detect E.coli(E.coli).Due to the excellent electrochemical activities,abundant functional groups,and?-?conjugated structure of TAPP and TDC,the constructed TAPP-TDC-COF-based electrochemical sensor exhibits high electrochemical response and strong binding to the targeted aptamer chain interact,so that Escherichia coli can be detected sensitively.In the range of 10?10⁸CFU m L^-1,both electrochemical impedance spectroscopy(EIS)and differential pulse voltammetry(DPV)showed extremely low detection limits of0.17 CFU m L^-1and 0.38 CFU m L^-1,respectively.In addition,the TAPP-TDC-COF-based electrochemical sensor has high selectivity to E.coli,good stability and regeneration ability,and practicality in bread and milk media.This paper proposes a new idea of constructing electrochemical biosensors based on porphyrin-based COF materials.Such biosensors can be extended to other targets and further explore the application value of COFs in the sensing field.