Synthesis Of Ionic Liquid Functionalized Metal-Organic Framework Compounds And Photoelectrochemical Immunosensing Study

Photoelectrochemical immunosensing is a newly developed analytical technique combining the merits of photoelectrochemical sensing and immune reaction.The basic principle for photoelectrochemical sensing can be depicted as following:upon being illuminated with light,the electrons on the valence band of the photoactive material can be excited to the conduction band,and then transferred to the electrode surface or the solution to form photocurrent response,thereby realizing quantitative assay of the target analyte.Compared with the traditional electrochemical and optical equipments,it has the advantages of high sensitivity,simple equipment,low-cost and easy miniaturization.The photoactive material is the keypoint ofphotoelectrochemical immunosensors.However,the photoelectric conversion efficiency of the commonly used photoactive materials are still unsatisfied,therefore,it is necessary to synthesize novel photoelectric active materials to improve the photoelectric conversion efficiency.In this dissertation,metal-organic frameworks functionalized with ionic liquid were synthesized and used as photoactive materials to construct photoelectrochemical immunosensors to achieve high sensitivity and specificity for tumor marker assay.The main contents are detailed as following:?1?A novel metal-organic framework nanocrystals?Zn-MOF?was synthesized by using a carboxyl functionalized ionic liquid as functional monomer and Zn²⁺as central metal ion under hydrothermal conditions.Gold nanoparticles functionalized with 1H-imidazolium-1,3-bis?2-aminoethyl?bromide?IBABr?ionic liquid were embedded within Zn-MOF by in-situ reduction of HAuCl₄ in the nanopores of Zn-MOF using acetic acid as a reducing agent to produce IBABr-Au NP@Zn-MOF nanocomposite.Zn-MOF and IBABr-Au NP@Zn-MOF were thoroughly characterized by FTIR,TEM,SEM XPS and nitrogen-adsorption surface area analysis method.IBABr-Au NP@Zn-MOF nanocomposites were deposited onto a glassy carbon electrodeand used as photoactive element to fabricate a label-free photoelectronche-mical?PEC?immunosensor by immobilizing anti-squamous cell carcinoma antigen?anti-SCCA?on the modified electrode through glutaraldehyde crosslinking process.The principle of SCCA sensing is based on the decreased electron and mass transfer after SCCA was bound to anti-SCCA on the electrode surface.The photocurrent decline??I=I₀-I?shows a good linear relationship to the logarithm of SCCA concentration[lg C_SCCA(ng mL^-1)]in the range from 5.0 pg mL^-1to 15.0 ng mL^-11 with a detection limit of 2.34pg mL^-1?S/N=3?.Under optimized conditions,the immunosensor provides high selectivity and sensitivity towards SCCA with good reproducibility and stability.The photoelectrochemical immunosensor was successfully used for determining SCCA in clinical human serum samples and the results are comparable to ELISA,demonstrating its potential for simple miniaturized immunosensor.?2?BDBMBIm?PF₆?₂ ionic liquid was used as functional monomer to coordinate with zinc ions to synthesize metal-organic framework?Zn-NMOF?nanocrystals using a one-step solvothermal method.Ammonium molybdate and thiourea were introduced into the pores of the as-prepared Zn-NMOF under vacuum.After being filtered,the solid mixture was transferred to a ceramic vessel.Then,the mixture was heated to220 ^o C in a tube furnace under the protection of nitrogen.Keeping 10 h,the product was annealed at 600 ^o C for 3 h to produce ZnS/C/MoS₂ nanocomposite.ZnS/C/MoS₂nanocomposite was thoroughly characterized by FTIR,TEM,XRD,XPS and nitrogen-adsorption surface area analysis method.CEA photoelectrochemical immunosensor was fabricated by immobilizing CEA primary antibody onto the ZnS/C/MoS₂ nanocomposite modified galssy carbon electrode surface,after crosslinking with glutaraldehyde vapor and blocking unspecific binding sites by BSA.After specific recognizing CEA,the sensing platform was further interacted with the CEA secondary antibody modified with gold nanoparticles and alkaline phosphatase marked?ALP-Au-Ab₂?.Based on the high catalytic performance of the enzyme,alkaline phosphatase?ALP?oxidizes vitamin C magnesium phosphate?AAP?to produce ascorbic acid?AA?.The produced AA can be captured by the photogenerated holes from the ZnS/C/MoS₂ nanocomposites to output photocurrent.Under the optimized experimental conditions,the photocurrent decline??I=I-I₀?beforeandafterAAPwascatalyzedby ALP-Au-Ab₂/CEA/Ab₁?BSA?/ZnS/C/MoS₂/GCE has a good linear relationship with the logarithm of CEA concentration[lg C_CEA(ng mL^-1)]in the range from 2.0 pg mL^-1to 10.0 ng mL^-1,and the detection limit is 1.30 pg mL^-1?S/N=3?.This immunosensor can be used for determining CEA in clinical serum samples,and the detection result has no significant difference compared with the chemiluminescence method.The PEC immunosensor has great potential for detecting tumor markers in blood samples clinically.