Analytical Applications Of The Enzyme Mimics Properties Of Transition Metal Fe Doped MOFs And Its Derivatives

Natural enzymes are produced by living cells that catalyze all chemical reactions in an organism.They are usually made of proteins,but a few of them are made of RNA.Natural enzymes have the advantages of high activity,high specificity and good selectivity.Based on these advantages,natural enzymes are used in food processing,medical care,factory production and many other fields.However,the application of natural enzymes is limited by the complexity of purification,the difficulty of storage and the harsh requirements on reaction conditions.Since 2007,Yan's research group has found that Fe₃O₄of different sizes has different peroxidase activity.This discovery has inspired researchers to explore artificial enzyme mimics,which have been developed in recent years with the advantages of simple synthesis,good stability and controllable activity.Metal-organic frameworks(MOFs)have become a research hotspot in the field of nanozymes due to their advantages such as adjustable pore structure and large specific surface area,which are beneficial to the adsorption and enrichment of substrate molecules around the active site.However,the preparation of high activity mimetic enzymes that can replace natural enzymes is still a difficulty in the field of nanozyme research.Based on the above research,we took MOFs as precursors and doped them with transition metal Fefor the purpose of improving the catalytic activity to prepare two novel nanozymes.Through a series of characterization methods,the successful synthesis of the nanoenzyme was proved,which of the catalytic activity was evaluated and its catalytic mechanism was discussed.UV-vis spectroscopy method was established and successfully used for the determination of acetylcholinesterase,hydrogen peroxide,glutathione,mercury ion(?),Specific contents are studied as follows:1.The activity of acetylcholinesterase was determined by FeCo/CNT-based oxidase-like nanozymeFe³⁺was added into Zn₁Co₁-BMOF by a double solvent method,which prevented the aggregation of Fe³⁺on Zn₁Co₁-BMOF.The competitive coordination of Zn²⁺and Co²⁺can make the distance between Co²⁺and Co²⁺wide and prevent the accumulation of Co.Then,FeCo alloy wrapped by nitrogen-doped carbon nanotubes(FeCo/CNT)was obtained by carbonization in nitrogen atmosphere at 800 ^oC for 2 h.The FeCo/CNT was characterized by SEM,TEM,XRD,Raman and XPS.The morphology,crystal form and valence state of the FeCo/CNT were analyzed.The Michaelis constant(K_m)of FeCo/CNT is 0.5307 m M,which indicates that the nanomaterial has good affinity to TMB.The catalytic mechanism of FeCo/CNT was investigated by free radical trapping experiments.The experiments showed that O₂^·-,·OH and¹O₂free radicals were produced in the catalytic process of FeCo/CNT.Acetylcholinesterase(ACh E)can catalyze acetylthiocholine chloride(ATCh)to produce thiocholine(TCh),and TCh can inhibit TMB oxidation.Based on this principle,we constructed a fast,sensitive and intuitive detection of ACh E activity.The linear range presents two segments,0.4?60m U/L and 60?1000 m U/L respectively,with the detection limit of 0.4 m U/L.The method was successfully applied to the determination of ACh E activity in human blood erythrocytes,and the results were in good agreement with the traditional Ellman method,which indicated that the system could sensitively detect ACh E activity in human blood erythrocytes and had a good clinical application prospect.2.Two-dimension bimetallic Ni/FeMOF nanosheet composites as peroxidase-like nanozyme for colorimetric assay of multiple targetsTwo-dimensional bimetallic Ni/FeMOF nanosheets were synthesized by a simple two-step ultrasonic synthesis strategy at room temperature.Fistly,two-dimensional Ni-MOF with layered structure was prepared by ultrasonic-assisted stripping method,and then Fe-MOF was formed in situ on two-dimensional Ni-MOF by using Fe³⁺as metal nodes and terephthalic acid as organic ligand.The morphology,crystal type and valence states of components of two-dimensional Ni/FeMOF nanosheets were investigated by means of SEM,TEM,XRD,Raman and XPS.Two-dimensional Ni/FeMOF nanosheets exhibited weak oxidase-like and strong peroxidase-like,the peroxidase-mimicking capability of the two-dimensional Ni/FeMOF nanosheets increased by 14-fold and 3-fold,respectively.In the of kinetics,we accidentally found that the Michaelis constant(K_m)of two-dimensional Ni/FeMOF nanosheets for H₂O₂was 0.037 m M,which the K_mis 1%of the horseradish peroxidase(HRP),indicating that the two-dimensional Ni/FeMOF nanosheets had a strong affinity for H₂O₂.The reactive oxygen trials indicated that the two-dimensional Ni/FeMOF nanosheet can efficiently catalyze the decomposition of H₂O₂to generate the·OH radical and O₂^·-,which can oxidize TMB to ox TMB from colorless to blue.Glutathione(GSH)can significantly inhibit the peroxidase activity of two-dimensional Ni/FeMOF nanosheets and inhibit the oxidation of TMB.However,after further introduction of Hg²⁺,due to the special affinity of Hg²⁺to the mercaptan bond in GSH,the inhibition of TMB oxidation can be restored.Based on these findings,method of detection for H₂O₂,GSH and Hg²⁺targets can be constructed.The linear range of H₂O₂was 0.01?1.5?M and 1.5?100?M,respectively with the detection limit of 10 n M.The linear range of GSH was 0.02?100?M with the detection limit of 10 n M.The linear range of Hg²⁺is 0.1?200?M with the detection limit is as low as 100 n M.The method was successfully applied to the detection of Hg²⁺in Jialing River water with the recovery of 98.41%?102.04%,which the results are satisfactory.