Synthesis Of Core/Shell Molecularly Imprinted Microspheres By Surface Reversible Addition-fracture Chain Transfer Technique For The Specific Enrichment Of Aflatoxin B₁ In Corn Samples

Aflatoxin B₁?AFB₁?is one of the most compelling mycotoxins,which seriously threatens human health.However,food sample matrix are complex,the process of mycotoxin enrichment and detection is tedious,time-consuming and costly.Molecularly imprinted polymers possess the features of structure predictability,specificity,high stability,etc.,which can effectively simplify the operation process,reduce the cost as well as improve the detection sensitivity when applied for separation and enrichment of trace harmful substances in food samples.In this study,the reversible addition-fragmentation chain transfer?RAFT?technique was first applied for the preparation of surface molecularly imprinted polymers of AFB₁based on magnetic nanoparticles?AFB₁-MMIPs?.The synthesis procedure of imprinting materials has been optimized for each stage at the aid of morphological characterization and performance valuation.The resulting AFB₁-MMIPs have been successfully applied for the separation and enrichment of AFB₁ in corn real samples.It is participated that our work would provide certain theoretical and technical support for relevant research and application work.Firstly,a surface molecularly imprinted polymers of AFB₁ based on silicon microspheres was firstly prepared by RAFT polymerization.Characterization of intermediate product of each step was performed to verify the successful preparation of silicon matrix core/shell molecularly imprinted polymers?Si-MIPs?of AFB₁.The identification performance of the as-prepared MIPs for AFB₁ was investigated under optimal adsorption conditions.The results showed that the equilibrium adsorption capacity of Si-MIPs for AFB₁ was higher than that of silicon-based non-molecularly imprinted polymers?Si-NIPs?,and the imprinting factor?IF?was up to 3.07.It is verified that specific cavities formed in Si-MIPs during the polymerization process,indicating that it is feasible to imprint AFB₁ on the surface of microparticles by using RAFT technology.Then AFB₁-MMIPs was synthesized via RAFT polymerization on the surfaces of silanized ferroferric oxide?Fe₃O₄@Si O₂?nanoparticles in toluene-methanol solution?9:1,v:v?using 5,7-Dimethoxycoumarin?DMC?as dummy template,methacrylic acid?MAA?as monomer,Ethyleneglycol dimethacrylate?EGDMA?as cross-linker,2,2-azobisissobutyronitrile?AIBN?as initiator.To achieve best saturated adsorption capacity and excellent specificity of AFB₁-MMIPs,the parameters of synthesis?the amount of MAA,molar ratio of DMC and MAA,the volume of solvent?,conditions for adsorption and elution of AFB₁?the solvent for adsorption,adsorption time,the solvent for elution,solvent volume and number of times for elution?were optimized.The intermediate product of each step and the final imprinted material were characterized by using scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,UV-visible spectrophotometer?UV-vis?,Fourier Transform Infrared Spectrometer?FTIR?,thermogravimetric analyzer?TGA?and dynamic light scatterometer?DLS?.The results showed that the MMIPs sphere prepared by using 6?L of MAA and 24 m L of the solvent?toluene-methanol solution?based on 16.5 mg Fe₃O₄@Si O₂ nanoparticles was highly homogeneous and monodispersity?PDI=0.242?.The equilibrium adsorption experiments were carried out under optimized condition where the molar ratio of DMC to MAA was 1:4 and acetonitrile-water?96:4,v:v?was used as an adsorption solution.The maximum IF was 2.01.The saturated adsorption capacity of MMIPs was 1198 ng/mg achieved after80 min dealing with AFB₁ spiked samples at the concentration of 8000 ng/m L.The adsorption amount of MMIPs for AFB₁ is 2.68-and 2.51-fold higher than those for OTA and ZEN in the competitive recognization experiment for AFB₁ over OTA and ZEN.The recovery rate was about 95%after twice elution with 1 m L methanol-acetic acid?90:10,v:v?.In conclusion,the as-prepared MMIPs showed uniform morphology,good dispersibility,high adsorption capacity,good specificity and fast adsorption.Finally,the as-prepared MMIPs was used for the separation and enrichment of AFB₁ in corn samples,and the performance was evaluated via quantitative detection of AFB₁using enzyme linked immunosorbent assay?ELISA?.Under the optimum MMIPs feed?25 mg?,results obtained from the as-prepared AFB₁ spiked corn samples showed that the average recoveries were ranged from 88.5%to 107.4%.In conclusion,the AFB₁-MMIPs synthesized in this study can be used for separation and enrichment of AFB₁ in real sample.