| Food safety is a big problem in people's livelihood.Therefore,the development of fast and convenient methods for the detection of mycotoxins has become critical.Aptamers are widely used in the detection of mycotoxins in food due to their high specificity and good sensitivity.In this experiment,a series of aptasensors were constructed by using covalent organic frameworks(COFs),metal organic frameworks(MOFs),black phosphorus nanosheets as modified materials for the detection of mycotoxins ochratoxin A,aflatoxin B1 and zearalenone in food.This research is divided into the following four parts:(1)An aptasensor based on a portable electrochemical workstation was proposed for the quantitative detection of zearalenone(ZEN)utilizing a screen-printed electrode(SPE)and a U-disk electrochemical workstation to measure the catalytic current of Au NPs@Ce-Tp Bpy COF materials to the reduction of peroxidation by chronoamperometry(i-t)in tris-acetic acid buffer solution(p H 7.0).When there is ZEN in the system,ZEN will specifically bind to the ZEN aptamer,which hinders the transfer of electrons and reduces the catalytic current of Au NPs@Ce-Tp Bpy COF for reduction of hydrogen peroxide.The quantitative detection of zearalenone toxin is achieved by the reduction value(?I)of the catalytic current.The results show that the prepared aptasensor has a good linear relationship between the response current(?I)and the logarithm of the zearalenone toxin concentration in the range of 0.01ng/m L-100 ng/m L.The linear equation is ?I= 0.401 lgc+1.548 with the linear correlation coefficient of 0.9906,and the detection limit was 0.389 pg/m L(S/N=3).The method is convenient to use,and can meet the needs of detection in situ with high selectivity and specificity for ZEN.(2)A multivalent biotinylated bioscaffold was designed for the sensitive detection of ochratoxin.In this method,streptavidin-conjugated horseradish peroxidase was used as a signal marker,and a visualized biosensor was constructed based on carboxylated magnetic beads for the sensitive detection of ochratoxin.In the presence of H2O2,horseradish peroxidase can oxidize TMB from colorless to blue,and the multivalent biotinylated bioscaffold can bind more streptavidin horseradish peroxidase,thereby amplifying the signal.Absorbance of oxidized TMB at 450 nm was measured using a UV spectrophotometer.In the range of 0.01 ng/m L-500 ng/m L,the absorbance showed a good linear relationship with the logarithm of the ochratoxin concentration,the linear equation was ?A = 0.203 lgc + 0.482,the linear correlation coefficient R2 = 0.994 with the limit of detection of 8.57 pg/m L(S/N=3).This sensor has the characteristics of high sensitivity,simple operation and signal amplification.(3)A two-dimensional layered covalent organic framework material loaded with gold nanoparticles was proposed as an electrode modification material,and streptavidin-labeled alkaline phosphatase was used as a signal label to construct an ochratoxin aptasensor.Under the catalysis of alkaline phosphatase,disodium p-nitrophenyl phosphate can be hydrolyzed to produce p-nitrophenol.The current response signal of p-nitrophenol was detected by differential pulse voltammetry.In the range of 0.005 ng/m L-100 ng/m L,the response current showed a good linear relationship with the logarithm of the ochratoxin concentration,the linear equation was ?I = 0.7477 lgc+2.0829,the linear correlation coefficient R2 = 0.9946,and the limit of detection was 1.67 pg/m L(S/N=3).(4)A method of constructing aflatoxin aptasensor with black phosphorus nano sheet loaded with gold nanoparticles as electrode modification material,Ce-MOF as signal label and prism DNA nano structure modified electrode as recognition interface is proposed.The hybridization between prism DNA and primer probe was used to trigger rolling circle amplification(RCA)on the electrode surface,and then the complementary chain modified with Au NPs@Ce-MOF is bound to the amplification chain to provide electrochemical signals.In the range of 0.024 ng/m L-100 ng/m L,the response current showed a good linear relationship with the logarithm of aflatoxin concentration,the linear equation was I = 6.4181 lgc+11.975 with the linear correlation coefficient of 0.9973,and the detection limit was 1.48 pg/m L(S/N=3). |
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