| The adulteration of edible oil caused by "gutter oil" fake edible vegetable oil seriously endangers the health of consumers.At present,the traditional instrument analysis method with high accuracy and stability is often used in the detection of edible vegetable oil adulteration,but these instruments are expensive,bulky and difficult for non-professionals to operate,so it is difficult to realize the rapid detection of edible vegetable oil adulteration.Electrochemical immunosensor has become an effective method for the identification of adulteration of edible vegetable oil due to its short detection time and good operation accuracy.It was found that capsaicinoids could be used as a marker of "gutter oil" for the detection of adulteration in edible vegetable oil.In this paper,capsaicinoids antibody was used as recognition element,and the recognition mechanism of capsaicinoid antibody was studied by computer-aided modeling.The construction method of electrochemical immunosensor for capsaicinoid adulteration markers in edible vegetable oil was explored,which mainly included the following contents:(1)The core component of the capsaicinoid immunosensor is the capsaicinoid antibody,and it is important to identify the key recognition sites of the capsaicinoid antibody for the construction of the immunosensor.The software MOEv2018.01 was used to conduct homologous modeling and molecular docking research on the variable region of capsaicinoid antibody,and the important recognition sites and key forces of the interaction between the antibody and capsaicinoids were identified:Tyr30 of L-CDR1 formed hydrogen bond with the capsaicinoids,Tyr24 on L-CDR1 and Tyr27 on H-CDR1 form a C-H…? non-bonded weak interaction with the capsaicinoids,and the common recognition sites of His26 on H-CDR1,Tyr44 on H-CDR2 and Gly94 and Phe95 on H-CDR3 all form van der waals forces with capsaicinoids.The recognition mechanism of capsaicinoid antibody was revealed,and the recognition sites of capsaicinoids were found to be amide groups,long-chain alkyl groups and benzene rings,which provided theoretical support for the subsequent construction of highly sensitive immunosensors.(2)On the basis of the above,an immunosensor based on double-signal amplification strategy was constructed for detecting capsaicinoid adulterated markers in edible vegetable oil.In order to improve the sensitivity of the immunosensor,prussian blue-gold nanoparticles(PB-AuNPs)was prepared by electrodeposition method,and characterized by scanning electron microscopy,energy spectrum analysis and electrochemical methods.A double signal amplification electrochemical immunosensor based on thionine/prussian blue-gold nanoparticles(TH/PB-AuNPs)was constructed by layer assembly method.PB-AuNPs provided better electrical conductivity,while TH enhanced the stability of electron transfer and the electrochemical performance of the sensor.Under the optimal conditions,the linear range of the prepared immunosensor was 0.1?1,000 ng/mL.It has been successfully applied in the actual samples of adulterated markers of capsaicinoids in edible vegetable oil.(3)In order to further improve the sensitivity of the immunosensor,a competitive electrochemical immunosensor for capsaicinoids was constructed based on nano-iron oxide@ceric oxide(Fe3O4NPs@CeO2)modification.Capsaicinoids reacted with antibody by competing with antigen and thus had a corresponding effect on electrical signals.The electrodes were modified by Fe3O4NPs@CeO2 with high conductivity and strong redox property,and the sensitivity of capsaicinoid immunosensor was further enhanced.The performance of the capsaicinoid immunosensor was studied by different electrochemical methods,which showed good stability and sensitivity.Under the optimal test conditions,the detection limit of the immunosensor was 0.33 pg/mL in the linear range of 10-3?104 ng/mL. |
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