Study On The Detection Of Aflatoxin B1 Based On Etched/Deposited Gold Nanorods

In recent years,food poisoning caused by mycotoxin contamination of food has occurred in an endless stream,of which aflatoxin B1（AFB1）is the most widely polluted and harmful.Among the methods for detecting AFB1,the enzyme-linked immunosorbent assay（ELISA）has the advantages of simple operation,high throughput,and rapid detection,which is suitable for real-time field detection.Traditional ELISA is overly dependent on biological enzyme activity and prone to false-positive signals,while the introduction of nanotechnology has brought a new direction to ELISA,and improved ELISA technology based on nanomaterials has been widely dev eloped.In this study,the unique plasma properties and good photothermal effects of gold nanorods（Au NRs）were used and combined with the traditional ELISA to achieve rapid and portable detection of AFB1 with dual-signal detection.The main research contents are as follows:（1）Colorimetric/photothermal dual-mode detection of AFB1 by enzyme-assisted Au NRs etching.Detection probes（MNPs@CAT@Apt）were synthesized using magnetic nanoparticles（MNPs）as carriers to enriched catalase（CAT）and coupled AFB1 nucleic acid aptamers（Apt）.Based on the principle of ELISA,the Apt and the encapsulated antibody act as recognition elements to identify the target in a sandwich structure on a 96polystyrene microtiter plate.Au NRs with the longitudinal plasmon wavelength（LPW）of 738nm was selected as the substrate,and MNPs@CAT@Apt was used to control the H₂O₂ concentration to promote the etching of Au NRs.Under the naked eye and thermometer measurement,the output color and temperature change were used as dual signals to quantify the concentration of AFB1.Meanwhile,the dual-mode detection of AFB1 in food was realized.Under the optimum conditions,the blue shift of LPW of Au NRs increased with the increase of AFB1 concentrat ion in the linear range of 10^{-1 3}～10^-8 g/mL,the color of the solution gradually changed from blue-purple to gray-green,and the temperature difference between Au NRs before and after heat generation decreased with the increase of AFB1 concentration.The detection limits of colorimetric signal and thermogenic signal were reached 8.636×10^{-1 4} g/mL and 2.790×10^{-1 4}g/mL.The method was applied to the detection of soy sauce,milk,peanuts,cornflakes and chilli powder,and the results were on par with those of commercial kits,the colorimetric effect was more obvious and the sensitivity was lower,which could meet the detection of AFB1 in a variety of foods.（2）Colorimetric/photothermal dual-mode detection of AFB1 by tea polyphenols controlled silver deposition o n Au NRsTo enhance the applicability of the assay,a metal chelator,disodium ethylenediaminetetraacetic acid（EDTA·2Na）,was used in place of the biomimetic enzyme commonly used in conventional ELISA.The detection probe（EDTA·2Na@Apt）was prepared by EDTA·2Na and Apt,and the target AFB1 was recognized by the probe and antibody.The chelation effect of EDTA·2Na for Fe³⁺and the complexation reaction between tea polyphenols（TP）and Fe³⁺were used for the competion of Fe³⁺in the system,to achieve the purpose of controlling the TP concentration.Silver deposition on Au NRs was mod ulated by TP,thereby changing the UV-Vis absorption spectrum and photothermal effect of Au NRs,and the color of the solution.The detection limit of colorimetric signal of this method was 2.848×10^{-1 3}g/mL,and the detection limit of photothermal signal was1.547×10^{-1 3}g/mL.The linear range of the dual signals was 10^{-1 2}～10^-7 g/mL.This method was used for the detection of AFB1 in liquor,milk,paprika,bean paste,and bread,and the response of dual signal was more sensitive than that of ELISA kit,which could meet the detection of AFB1 in various foods.