Synthesis Of Porous Nanomaterials And Application In Isolation And Detection Of Aflatoxin B₁

Aflatoxins are toxic metabolites produced by Aspergillus flavus and parasitic Aspergillus.It can enter animal and human bodies through the food chain and produce toxicity,especially in liver.Long-term consumption of foods with aflatoxin can cause liver damage and liver cancer,which seriously threatens the health and even life of humans and animals.The toxicity of aflatoxin B₁ is the strongest of 20 aflatoxins.The separation and detection of aflatoxin B₁ have always been a research hotspot in the food field.The existing separation methods consume a lot of toxic organic solvents in the process of operation,which pollutes the environment.In addition,these methods are cumbersome and have poor separation efficiency and specificity.In this experiment,the aptamer was assembled on the magnetic composite material to develop the technology based on the pretreatment of aflatoxin B₁.At present,the methods of detecting aflatoxin B₁mainly include enzyme-linked immunosorbent assay?ELISA?,liquid chromatography-tandem mass spectrometry?LC/MS-MS?,and high-performance liquid chromatography combined with fluorescence detection methods?HPLC-FLD?.However,most of these methods have complicated procedures,expensive instruments,and poor specificity.Electrochemical biosensor has attracted the attention of researchers in aflatoxin B₁detection.It has advantages of simple operation,low cost,fast detection speed and high sensitivity.In recent years,new nanomaterials have been widely used in electrochemical sensing due to their excellent properties.Porous anodized alumina?PAA?membrane has the advantages of adjustable shape,size and controllable ion transport law.If it is combined with electrochemical technology,it can greatly improve the detection sensitivity.Therefore,in this study,magnetic metal organic framework composites were used to separate aflatoxin B₁.The AFB₁-NH₂aptamer was immobilized on porous alumina membrane to construct nanochannel biosensor for detecting aflatoxin B₁.The main contents of this paper include the two aspects:1.Specific enrichment and separation of aflatoxin B₁ by aptamer-functional magnetic metal-organic frameworkFe₃O₄ nanoparticles were synthesized by solvothermal method,MIL-100?Fe?was modified by layer-by-layer assembly,carboxyl groups on MIL-100?Fe?were coupled by EDC-NHS reaction.The amino group of AFB₁ aptamer,and the carboxyl group were covalently bonded to construct a Fe₃O₄@MIL-100?Fe?@Aptamer composite structure.Based on the specific binding of the aptamer and AFB₁,the composite material was applied to adsorb and separate AFB₁.Scanning electron microscopy?SEM?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,vibrating sample magnetometer?VSM?and thermogravimetric analysis?TGA?were used to characterize the Fe₃O₄ and Fe₃O₄@MIL-100?Fe?.The results show that the synthesized Fe₃O₄ has a uniform spherical shape and a good crystal form.The specific surface area of Fe₃O₄@MIL-100?Fe?is 56.38 m2/g.It has good superparamagnetism,the magnetization intensity is 92 emu/g.Under the action of external magnetic field,it has fast separation speed.Fe₃O₄@MIL-100?Fe?has good thermal stability below 320°C.XPS test results show that the aptamer is successfully modified on Fe₃O₄@MIL-100?Fe?composite material.The composite material is used for the adsorption of AFB₁,and the adsorption equilibrium reaches within 60 min.2.Preparation of graphene oxide/aptamer/PAA membrane array nanochannel biosensor and its application in detection of aflatoxin B₁The PAA membrane prepared by the secondary anodization method was used as a template.The surface was modified using silane reagents and glutaraldehyde.And aldehyde groups were introduced on the surface.Using the condensation reaction of amino groups and aldehyde groups,the aptamer?containing amino groups?of AFB₁was modified on the surface of PAA membrane nanochannels.GO was modified on the surface of PAA membrane exploiting the?-?interaction between GO and aptamer.Then,the graphene oxide/aptamer/PAA membrane array nanochannel biosensor was constructed.SEM and XPS were used to characterize the prepared PAA membrane and the functionalized PAA membrane.Furthermore,an electrochemical workstation was used to apply a reduction potential of 0 V and Fe?CN?₆^3-was used as the electroactive probe.At this time,the current response is positively correlated with the flux of Fe?CN?₆^3-.After modification of GO,the charge density and steric hindrance of the nanochannel increase,the flux of Fe?CN?₆^3-decreases significantly,and the current response decreases.When AFB₁ is present,it competes with GO for AFB₁ aptamer,causing GO to fall off the PAA membrane surface.The nanochannel charge density and steric hindrance decrease,Fe?CN?₆^3-flux increases,and the current response recovers.The results show that the pore size of the prepared PAA membrane is about 200 nm,GO and aptamers can be successfully modified in the surface of PAA membrane.In addition,the array nanochannel biosensor has a good linear range?1-20 ng/m L?and low detection limit?0.3 ng/m L?for AFB₁.At the same time,the biosensor has good selectivity for AFB₁.The current response of the biosensor to other mycotoxins?such as ochratoxin A,aflatoxin B₂,and aflatoxin G₁?is less than 4 n A,much smaller than the current response of AFB₁?20 n A?.