Water-compatible Surface Molecularly Imprinted Magnetic Beads For Efficient Adsorption Of Patulin

Food safety is a hot economic and social issue in China.Developing efficient sample preparation technology is one of the key contents in food safety research field,and a universal and urgent target to be achieved for food safety monitoring.MIP is a macromolecule polymer having artificially generated recognition sites with shape,size and functionalities complementary to the target analyte within the pores of the polymer.Therefore,the template molecule can be specifically recognized and adsorbed in a complex matrix.Due to its flexible designability,simple fabrication,good stability,reusability and wide adaptability,it has been widely used in sample preparation,sensor and biological simulation.At present,molecularly imprinted polymers for small organic target molecules generally exhibit excellent molecular recognition performance in organic solution,while they are not water compatible,and seldom applicable in aqueous samples.However,the majority of food environmental and clinical sample are aqueous solutions of small organic molecules.Therefore,it is of great practical significance to develope molecularly imprinted polymers with excellent molecular recognition performance in aqueous solutions.Patulin(PAT)is a highly toxic secondary metabolite produced by filamentous fungi.It is carcinogenic and teratogenic and is often found in rotted apples,hawthorn,carrots and other fruits and vegetables.Being a water soluble mycotoxin,PAT is difficult to be separated from processed or semi-processed products.So it often contaminates the juice or jam,and is extremely harmful to human health.Up to date,the commonly used sample pretreatment method for juice with patulin is organic solvent extraction combined with solid phase extraction,which consumes a large amount of organic solvent and includes many steps.In this study,a core-shell water compatible surface molecular imprinted magnetic submicro-beads(MMIPs)were prepared via reversible addition-fragmentation chain transfer polymerization using hydrophilic monomers with strong affinity to patulin and structural analogs of PAT as template molecules.Further,polar polymer brushs were grafted from MMIPs by employing RAFT technique,which enhanced their water compatibility.A non-covalent molecular imprinting system was chosen to prepare PAT MMIPs,which utilized 6-HNA,AM,EGDMA and DMSO as the template,functional monomer,crosslinker and porogenic solvent,respectively.The molar ratio of 6-HNA,AM and EGDMA was 1:2:40.With the initiation by AIBN and control ofpolymerization by free RAFT reagent,the molecularly imprinted polymer layer was successfully grafted on the surface of the superparamagnetic silicon sphere.Then hydrophilic PAA molecular brushs were modified on the surface of the MMIPs via RAFT polymerization,which utilized AA,AIBN and RAFT reagent as the monomer,initiator and polymerization controller,respectively.The prepared water-compatible patulin MMIPs were characterized and analysis using transmission electron microscopy,scanning electron microscopy,atomic force microscopy,optical contact angle measurement,thermogravimetric analysis and vibrating sample magnetometers.The results show that the molecularly imprinted polymer layer on the surface of MMIPs is uniform,complete and hydrophilic.Using methanol-trifluoroacetic acid mixture(90:10,V/V)as the elution solvent,the PAT adsorption behaviours of the prepared MMIPs were tested in a 0.1 % Tween-20(p H=6)aqueous solution.The results of adsorption isotherm showed that the maximum adsorption capacities of MMIP-PAAs and MNIP-PAAs were 1798.5 and 538.2 ng/mg,reapectively.The imprinting factor was 3.34.The results of kinetic adsorption studies showed that the adsorption capacity of PAT for MMIP-PAAs at 120 min was 1650.8 ng/mg,which was 98 % of the maximum adsorption capacity when the PAT input concentration was75 ?g/m L.In addition,MMIP-PAAs has good specificity and selectivity in distinguishing PAT and its structural analogue(HMF),which is a common interferent for PAT determination in juices.Morever,It can be reused at least 5 times.