Application Of Metal-organic Framework Materials Loaded With Enzymes In Colorimetric Detection

Enzyme is a kind of biological macromolecular catalyst with high selectivity and efficiency.However,due to its poor chemical and thermal stability and low reusability,its practical application has been hindered to some extent.For improving the stability and recyclability of enzymes and to broaden the development prospects of enzymes in the field of biological application in recent years,the immobilization of enzymes with porous materials has been widely studied.Metal-Organic Frameworks(MOFs)are a new type of porous materials consisted of metal nodes and organic ligands,which have a series of unique physical and chemical properties,such as high specific surface area and pore volume,adjustable porosity,and easy functionalization.Many MOFs-enzyme composites are far superior to free enzymes in terms of catalytic performance.Therefore,MOFs as the carrier materials of enzyme immobilization platform have attracted more and more researchers'research interest.In this paper,we mainly studied two different MOFs immobilized glucose oxidase(GOx)catalyst composites and applied them to colorimetric sensing system,and discussed the advantages and disadvantages of MOFs immobilized enzyme in colorimetric sensing system.The main research contents are as follows:Chapter one:ZIF-8 immobilized cascade catalyst and its application in colorimetric detection.Poly(1-vinylimidazole)(PVI)was used to link glucose oxidase(GOx)and hemin together,and the composite catalyst was placed in the aqueous solution of ZIF-8 precursor to synthesize GOx&PVI-hemin@ZIF-8 composite materials at room temperature to construct a cascade catalytic system,which is used for detecting the concentration of glucose in the solution.In the presence of dissolved oxygen,GOx catalyzes glucose to produce H₂O₂,at this time,hemin linked with GOx can catalyze the reduction of H₂O₂ in situ,and chromogenic reaction occurs in the presence of chromogenic reagent,so as to realize the colorimetric detection of glucose.In addition,the maximum catalytic efficiency of the cascade was achieved by adjusting the optimal molar ratio of GOx to hemin.The prepared GOx&PVI-hemin@ZIF-8 composites not only exhibited enhanced catalytic activity,but also exhibited long-term and reusable catalytic activity for the cascade reaction,which was attributed to the protective effect of ZIF-8 on guest biocatalyst.Chapter two:Colorimetric detection based on metal-metalloporphyrin gel MOFs immobilized enzyme.Metal-metal-porphyrin gel(MMPG)with hierarchical mesoporous structure was synthesized by solvothermal method,and GOx was immobilized in Fe-MMPG to construct a cascade catalytic system.The formation conditions and pore structure of Fe-MMPG were systematically studied,and the mesoporous structure of the gel was controlled by adjusting the concentration of the reactants.Fe-MMPG-5(Fe-porphyrin ligand at a concentration of 5 m M)has a good pore structure for efficient encapsulated GOx.Compared with the free GOx,the catalytic activity of the GOx@Fe-MMPG-5 composite material is significantly enhanced,and the GOx@Fe-MMPG-5 composite material provides excellent performance for colorimetric sensing of glucose.