Construction Of Sensing Platform Based On Metal-organic Framework And Gel Material For Food Toxin And Pesticide Detection

The biological and environmental hazards caused by mycotoxins and pesticide residues in food cannot be ignored.Therefore,it is important to develop rapid and sensitive analytical methods for the detection of mycotoxins and pesticide residues.Sensing platforms based on metal-organic framework（MOF）and gel（MOG）materials are widely used for the detection of food toxins and pesticide residues because of their sensitivity and short time consumption.In this thesis,Mn MOF,Mn-ZIF-67-0.4,TCPP-Cu Co₂O₄ with nanoenzyme properties and Fe MOG were synthesized and used to construct a sensing platform for fungal toxins and pesticide residues.The research work in this thesis is divided into four parts as follows.（1）Aflatoxin B1（AFB1）is the most common class of contaminants in natural foods,and it is also the most toxic and carcinogenic.In this work,metal organic framework nanoenzymes（Mn MOF）with catalase-like properties were synthesized.The Mn MOF-C was obtained after high-temperature carbonization,and the composite Pt NPs@Mn MOF-C was obtained by doped platinum nanoparticles,which was found that its catalytic capacity could be further enhanced.The composite was used as a marker to prepare the AFB1 aptamer sensor.The aptamer with high affinity and high specificity can be specifically bind to AFB1 and dissociates from the electrode surface,resulting in a reduced current signal catalyzed by Pt NPs@Mn MOF-C,thus achieving quantitative detection of AFB1 in food.In the range of 0.001 to 100 ng/m L,the response signal gradually decreased as the concentration of the target AFB1 increased.The aptasensor constructed in this work has high sensitivity and short time consuming,and can be used for AFB1 detection in real rice samples,showing good application prospects.（2）A bimetallic organic framework material Mn-ZIF-67-0.4 was prepared by a one-pot method.A colorimetric sensor for dopamine detection was construct based on excellent oxidase-like properties of Mn-ZIF-67-0.4.The response signal（absorbance difference at 652 nm）showed a good linearity with DA concentration under the optimal conditions,the linearity range was 0.4-80μmol/L,with a linear correlation coefficient of 0.9952 and and the regression equation wasΔA=0.0145 c+0.1303.The proposed DA colorimetric sensing platform can be used for the determination of DA in human serum,which has the advantages of low cost,short time consumption and sensitive detection.（3）The acetylcholinesterase sensor was constructed using a novel metal organic gel（Fe MOG）with good electrical conductivity.After heat treatment at 900℃,Fe MOG-N-C was obtained and the resistance value could be further reduced.ACh E was immobilized onto the electrode using Au NPs@Fe MOG-N-C as the substrate conductive material.ACh E can catalyze the hydrolysis of acetylthiocholine chloride to generate the reducing thiocholine（TCh）,which had a characteristic oxidation peak at0.6 V.The pesticide can inhibit activity of ACh E,therefore,the generation of TCh was inhibited,resulting in a reduction of the oxidation peak current.Thus,sensitive detection of pesticides can be achieved.（4）The functionalization of Cu Co₂O₄ with TCPP can obtain TCPP-Cu Co₂O₄ with excellent peroxidase-like properties,which was used for the construction of trichlorfon colorimetric sensing platform.In the presence of H₂O₂,TCPP-Cu Co₂O₄ can oxidize colorless TMB to blue ox TMB,accompanied by a strong absorption peak at 652 nm.ACh E can specifically catalyze the hydrolysis of ATCh to TCh,which has a sulfhydryl structure and can reduce ox TMB,reducing the absorption peak at 652 nm.However,Trichlorfon can irreversibly inhibit the activity of ACh E and restore the absorption peak.Thus,a colorimetric sensing platform for the detection of acetylcholinesterase activity and trichlorfon was constructed.The method has the advantages of rapid detection,low cost and simple operation.The proposed sensing platform has a wide linear range of40-4000 ng/m L for trichlorfon detection with a linear correlation coefficient of 0.9904.In addition,the response signal of the platform（absorbance difference at 652 nm）showed a good linear relationship with ACh E activity when ACh E was in the activity range of 0.1-5 U/L.The proposed assay can be applied to the detection of trichlorfon in vegetables and has good application prospects.