Design And Synthesis Of Highly Efficient MOF-based Nanozyme And Its Application In Food Quality Control

Food quality control is one of the major issues related to food safety.Large instrument analysis methods that rely on professional and technical personnel are cumbersome in operation and require high sample requirements.Therefore,there is an urgent need to develop various efficient and convenient rapid detection methods.In recent years,metal-organic framework(MOF)-based nanozymes have become a research hotspot in the field of rapid food detection methods due to their enzymatic properties,controllable pore size and surface chemical properties of materials,ultra-high surface area and porosity,and structural diversity.There are many types of MOF based nanozymes with varying catalytic activities.Designing and synthesizing highly efficient MOF based nanozymes is of great significance for establishing highly sensitive methods for rapid food detection.Based on the chemical properties of MOF-based nanozymes,three different high-efficiency nanozymes have been designed and synthesized for the detection of components related to food quality control.The specific research content is as follows:(1)Two-dimensional metal organic framework(2D MOF)nanoparticles with iron porphyrin as ligand and copper ion as center were prepared,characterized by morphology and structure,and their catalytic fluorescence reaction conditions were optimized.Based on the inhibition effect of tannic acid on the fluorescence system,a high-efficiency fluorescence sensor is constructed,with a linear range of 5.0-100.0μM,a detection limit of 2.2 μM,good anti-interference and high accuracy.The recovery rate of added standard for the determination of tannic acid in beverages and red wine is 93.54%-105.28%,which is basically consistent with the determination result of HPLC.2D MOF fluorescence sensor has the advantages of simple operation,good sensitivity and low cost,and can realize the rapid detection of tannic acid in food.(2)Two dimensional iron metal-organic framework nanosheet(2D Fe MOF)was facilely synthesized at room temperature by simple stirring of iron salts and terephthalic acid ligand in a mixed solution containing triethylamine.Its morphology and structure were well characterized by transmission electron microscopy(TEM),atomic force microscopy(AFM),X-ray photoelectron spectroscopy(XPS)and X-ray spectroscopy.Its peroxidase mimicry activity was studied,and then based on the cascade reaction between xanthine oxidase and 2D Fe MOF,a visualization method for the detection of hypoxanthine(Hx)was constructed to evaluate the freshness of aquatic products After effective validation,this method presented wide linear range(5.0-500.0 μM),low limit of detection(3.29 μM),satisfied accuracy(recovery of94.78-99.85%),and good selectivity.By using this method,Hx content in shrimp samples at different storage time were determined.(3)Metalloporphyrin and gold nanoparticles(Au NPs)were fixed on the surface of hollow zeolite imidazole framework-8(HZIF-8)by cation exchange and cross-linking reaction.The obtained hybrid nanozyme Au/HZIF-8@TCPP(Fe)was completely characterized and the enzymatic reaction kinetic parameters of this composite nano enzyme were analyzed,indicating that it has good catalytic activity.Based on cascade reaction between choline oxidase and Au/HZIF-8@TCPP(Fe),a quick colorimetric method was established for choline detection in infant formula milk powder.After comprehensive verification,this method presented the merits of simple operation,satisfied detection limit(0.05 m M),wide linear range(0.05-2.0m M),high accuracy(recovery of 92.2%-105.2%)and nice selectivity.The content of choline in five brands of milk powder was determined by colorimetry,and the quantitative analysis of choline in infant milk powder was realized.