Preparation Of Aflatoxin B1 Molecularly Imprinted-SERS Chemosensor With The Aid Of Computer Simulation And Their Applications

With the general improvement of people's quality of life,the issue of food safety has received widespread attention.Aflatoxin(AFB)is produced by Aspergillus flavus and Aspergillus parasiticus,a class of toxic carcinogenic substances containing difuran rings and dicoumarins in their basic structure,often contaminated cereal crops such as peanuts,corn,etc.,causing food poisoning.Among which aflatoxin B1(AFB1)is the most toxic,it was classified as a class I carcinogenic substances by the World Health Organization in 1993.The commonly used methods for the detection of AFB1 include thin-layer chromatography(TLC),high performance liquid chromatography(HPLC)and enzyme-linked immunoassay(ELISA).TLC is simple and requires little equipment,but sample pre-treatment is complicated;HPLC requires expensive equipment and professional personnel,and the method is time consuming and requires a lot of organic reagents;ELISA is simple and sensitive,but the problem of false positives is difficult to solve.Therefore,it is of practical significance to develop a simple,rapid,selective and sensitive detection method for AFB1.Surface-enhanced Raman spectroscopy(SERS)technique is widely used in the field of food safety detection due to its high sensitivity and simple operation.In the actual sample detection,the detection system is often complex and the target is susceptible to interferents that make it difficult to analyze the spectral information of the target effectively.Molecularly imprinted polymers(MIP)are considered as a kind of synthetic materials with low cost,good stability and high selectivity,in which the presence of special cavities can achieve selective capture of the target.Therefore,this paper is devoted to the construction of a highly sensitive and selective MIP-SERS sensor for the rapid separation and detection of AFB1 by combining Surface-enhanced Raman spectroscopy with molecular imprinting technology.(1)The optimal monomer for the synthesis of DMIPs and the optimal binding ratio between template and monomer were screened from six commonly used functional monomers by computer simulation technique using 7-ethoxycoumarin as a dummy template,and the results showed that a more effective interaction between monomer and template existed at a ratio of 1:4 with N-isopropylacrylamide(NIPAM)as the functional monomer.Subsequently,dummy template molecularly imprinted polymers(DMIPs)was prepared using bulk polymerization approach based on the simulation results,Infrared spectroscopy proved the successful synthesis of DMIPs,and BET characterization showed that DMIPs have a large specific surface area(149.5 m² g^-1).Computer simulations proved that too much cross-linking agent will not affect the Pre-assembled structure of DMIPs and affect their specific adsorption performance.A series of adsorption experiments and studies on the adsorption mechanism demonstrated that DMIPs has good adsorption capacity and high mass transfer rate with an imprinting factor of 2.32,and DMIPs also has good selective adsorption capacity for AFB1.In addition,DMIPs was able to maintain its large adsorption capacity after several adsorption-desorptions.(2)Based on the previous work,DMIPs are used as solid phase extraction(SPE)materials to selectively extract aflatoxin B1 from peanuts and concentrate for SERS detection.The TA-Ag NPs MF substrate was prepared by self-assembly of thioctic acid(TA)modified Ag NPs at the n-hexane/water interface.The carboxyl group of TA can effectively capture AFB1 through hydrogen bonding and pull AFB1 to the hot spot of the substrate.Combined with the selective extraction of AFB1 by molecularly imprinted solid phase extraction,the sensitive detection of AFB1 in actual samples is realized.The research results show that the SERS substrate has good uniformity,stability and reproducibility.The dummy molecular imprinting-solid phase extraction-surface-enhanced Raman(DMISPE-SERS)sensor has a detection limit of 10^-7 g L^-1 for aflatoxin in peanuts,which meets the limit standard of the European Union(2×10^-6 g L^-1),the recovery is 93%-102%.