Development And Application Of Molecularly Imprinted Electrochemical Sensors For Mycotoxins Based On Ionic Liquids Improving Performance

Molecularly imprinted electrochemical sensors have the advantages of high sensitivity,low cost and good selectivity,and they are widely used in food and environmental analysis.However,they still have some shortcomings,which limit their applications.In this work,ionic liquid（IL）and magnetic field are introduced in the preparation of molecularly imprinted electrochemical sensors to improve their performance for mycotoxin detection.The details are as follows:1.Ionic liquid assisted molecular self-assemble and molecular imprinting for the detection of zearalenoneIn order to increase the number of molecularly imprinted sites,an ionic liquid assisted self-assembly molecular imprinting strategy was proposed.Firstly,an IL functionalized boron-doped ordered mesoporous carbon-gold nanoparticles composite（BOMC-IL-Au NPs）was used to modify the electrode,then the BOMC-IL-Au NPs/GCE was immersed into 4-aminothiophenol（4-ATP）solution and template solution in turn.Subsequently,the template molecules self-assemble onto the composite to form a dense template layer because of the hydrophobic interaction,π-π,and hydrogen bond between the template and IL/or 4-ATP.After electropolymerization,the template layer was embedded into the 4-ATP polymer and produced lots of imprinted sites.Zearalenone could be quantified from 5×10^-4 to 1 ng mL^-1 with a low detection limit of 1×10^-4ng mL^-1.This sensor was applied for the detection of zearalenone in real samples.2.Determination of patulin using dual-dummy templates imprinted electrochemical sensorHerein,2-oxindole and 6-hydroxynicotinic acid as the dummy templates,4-aminothiophenol as functional monomer and IL as electropolymerization electrolyte were employed to prepare molecularly imprinted polymer.2-Oxindole and 6-hydroxynicotinic acid had multiple groups and the obtained molecularly imprinted polymer possesses different types of imprinted sites,thereby achieving a better recognition capacity than that of single-dummy imprinted film.ILs regulated the density of molecularly imprinted film and facilitate effective molecular recognition.The composite of PtPd decorated N-doped porous carbon had good conductivity and large surface area,and amplified the signal.This sensor showed a detection range from 0.01 to 10μg L^-1,with a detection limit of 7.5×10^-3μg L^-1.It has been successfully applied for the detection of patulin in real samples.3.An effective ratiometric electrochemical sensor for the detection of ochratoxin A by using a magnetic field improving molecular imprintingThe molecularly imprinted polymer was prepared by cyclic voltammetry;during electropolymerization a magnetic field was introduced to regulate the molecularly imprinted polymer orientation for improving molecular recognition efficiency.A gold nanoparticles,ploy（IL）and flavin mononucleotide decorated carbon nanotubes-MoS₂ nanosheet composite（Au NPs/PIL-FMNS/CNT-MoS₂）was used as substrate to amplify signal and to provide reference signal.The peak current of Au NPs/PIL-FMNS/CNT-MoS₂ decreased with the increase of ochratoxin A concentration,while the peak current of ochratoxin A oxidation product increased.The ratio of the peak currents changed linearly with ochratoxin A concentration variation and was used for ochratoxin A quantification.Under the optimized conditions,the linear response range was 0.5-15μmol L^-1 and the low limit of detection was14 nmol L^-1.The sensor has been applied for the ochratoxin A detection in spiked samples and satisfactory results were achieved.4.A novel ratiometric electrochemical sensor for the detection of citrinin based on molecularly imprinted polymerA molecularly imprinted polymer based ratiometric electrochemical sensor was prepared for citrinin detection.The sensor was fabricated by electropolymerization,using thionine as monomer and citrinin as template.The IL decorated boron and nitrogen co-doped hierarchical porous carbon as supporter provided large surface for anchoring thionine and citrinin.Poly（thionine）not only acted as molecularly imprinted polymer,but also acted as reference probe.When[Fe（CN）₆]^3-/4-was adopted as indicating probe,the resulting sensor demonstrated a wide linear detection range(i.e.1×10^-3-10 ng mL^-1)and a low detection limit(i.e.1×10^-4ng mL^-1).The sensor has been applied to the detection of spiked citrinin in real samples.5.Antifouling molecularly imprinted polymer-based ratiometric electrochemical sensor for detection of zearalenoneIn this system,black phosphorus-graphene oxide with large surface area and good electrochemical property was used as substrate to amplify the signal;IL doped molecularly imprinted polymer endowed the sensing surface not only high recognition ability but also high capability to resist nonspecific adsorption.In addition,a magnetic field was introduced to regulate polymer structure during molecularly imprinted polymer preparation for improving the recognition efficiency of sensor.The signals of zearalenone and poly methylene blue served as response signal and internal reference signal,respectively.The peak current of zearalenone increased with the increase of zearalenone concentration,while the peak current of poly methylene blue decreased simultaneously;their ratio changed with zearalenone concentration variation.The sensor had high selectivity and reproducibility,thanks to the advanced antifouling molecularly imprinted polymer and the built-in correction from poly methylene blue.Its linear response range was 0.05-13μmol L^-1 and low limit of detection was 12.7 nmol L^-1.The sensor has been successfully applied to determine zearalenone in human serum.