Mimic Peroxidase-Based Signal Amplification For Rapid Detection Of Genetically Modified Components In Food

In recent years,due to their desirable traits including herbicide/disease tolerance,virus/insect resistance,delayed ripening,and improvement of nutritional content,the large-scale commercial production of genetically modified foods has brought enormous social and economic benefits.However,there are still risks associated with GM technology,such as environmental risks and potential food safety.The CaMV35S promoter and NOS terminator gene sequences are two specific exogenous sequences in most transgenic foods,so the detection of the CaMV 35S promoter or NOS terminator gene fragment can be judged to some extent that the sample is derived from the transgenic food.Based on this,the CaMV 35S promoter and NOS terminator gene sequences commonly used in transgenic plants were used as detection targets,and the quantitative detection of CaMV 35S promoter and NOS terminator target gene sequences was achieved by DNA biosensor technology and colorimetric method,respectively.The content of this paper contains two parts as follows:1.Ultrasensitive electrochemical genosensor for detection of the CaMV 35S gene in genetically modified foods based on Fe₃O₄-Au@Ag as nanoprobe.In this study,a sensitive sandwich electrochemical biosensor was designed to detect the CaMV 35S gene,which was organically combined using Au@Ag-loaded magnetic nanoparticles?Fe₃O₄-Au@Ag?as label of signal DNA probe?sDNA?.The sandwich-type genosensor was accomplished on the sensing interface of electrodeposite AuNPs and carboxylated multiwalled carbon nanotubes modified glassy carbon electrode?GCE?through the specific interaction between the capture probe?cDNA?and target CaMV 35S?tDNA?,and tDNA and the labeled sDNA.The sensitive detection was realized by the amplified reduction signal of H₂O₂ by taking advantage of the enhanced electrocatalytic activity of Fe₃O₄-Au@Ag nanocomposite.Under the optimized conditions,the increased reduction signal of H₂O₂ of the proposed biosensor was linear with the logarithm of target CaMV 35S in a wide range of 1×10^-16–1×10^-1010 M with a low detection limit of 2.31×10^-1717 M.This biosensor also displayed good stability,selectivity and reproducibility,which was applied for practical detection of genetically modified tomato with satisfactory results.2.Hemin-graphene hybrid nanosheets with intrinsic peroxidase-like activity for label-free colorimetric detection of NOS gene sequences.In this section,based on Hemin-graphene exhibits intrinsic peroxidase activity.We designed a sandwich hybridization method to detect of transgenic NOS?tDNA?by colorimetry.First,the thiol-modified capture probe?cDNA?was bound to the Fe₃O₄-Au nanoparticles via the Au-S bond,and hybridized with the NOS target sequence and the H-GNs-modified signal probe?sDNA?to form a sandwich structure.After magnetic separation,the tDNA and H-GNs-sDNA hybridized with Fe₃O₄-Au-cDNA were magnetically separated,and the supernatant was collected.The H-GNs-sDNA which was not hybridized in the supernatant was subjected to color reaction in TMB-H₂O₂system.After 3 minutes of reaction,the absorbance at 652 nm was measured by UV-Vis absorption spectroscopy,and then the absorbance value was changed according to the absorbance value.Quantitative detection of NOS target sequences.Under optimal conditions,the concentration of NOS gene is in the range of 0.5-100nM,and the absorbance at 652 nm is linear with the logarithm of NOS gene concentration.The minimum detection limit is 0.22 nM.The detection method can also be applied to the actual detection of transgenic tomatoes,and the results are satisfactory.