Construction Of Different SERS Probes And Their Detection Of Risky Substances In Foods

Hazardous substances in food are a major problem affecting ecological health,mostly due to the symptoms of poisoning complications after a certain amount of accumulation in the body.The harm caused to the human body includes the damage of various functions,such as nerve paralysis,dizziness,diarrhea and so on.So far,domestic food safety problems have emerged one after another,and the traditional detection methods are mainly mouse experiments,pathological analysis and biochemical tests.However,mouse experiments have time-consuming,low specificity and ethical issues.On the other hands,residual hazardous substances in food often exist in complex environments,and their content is relatively small.It is difficult to achieve effective trace residual monitoring by general detection methods,and complex pre-treatment processes are required.If food hazards can be detected with high accuracy,convenience and non-destructive trace detection,it will have a profound impact on food safety control and human health.Surface-enhanced Raman technology（SERS）is a powerful platform with the advantages of trace detection at the level of molecular biological detection.Researchers are committed to developing various qualitative and quantitative detection of hazardous substances based on SERS technology.The quality of SERS enhancement is related to the surface smoothness,particle spacing,density and material of the substrate.In this paper,different SERS probes were constructed to detect different types of hazards.Au NPs,GO-Au,Au@Si O₂ NPs,Au@MBN@Ag NPs,Ag NPs and monolayers all show good stability.The main research contents are as follows:1.The gold nanoparticles were immobilized and embedded on the monolayer graphene oxide framework by the in-situ reduction method to form a GO-Au loading compound.In addition to providing in situ reduction sites,the monolayer graphene oxide framework also has binding sites forπ-πstacking with aptamer RNA hybridization.Based on this,a GO-Au-saxitoxin-aptamer（GO-Au-Apt）was constructed,which was used to detect saxitoxin（STX）based on the probe using SERS technology.The aptamer modified with the signal molecule（Bodipy R6G）overcomes the problem of the weak Raman scattering cross section of STX,while improving the detection specificity and accuracy.In the reaction system,the combination of STX and Apt will destroy the surface structure of the GO-Au-Apt aptamer probe,so that the SERS signal changes with the concentration of STX.A standard working curve was established based on the STX concentration and the SERS intensity of the aptamer probe at the characteristic peak of 767cm^-1.The high specificity of the method was discussed through anti-interference experiments,and the quantitative analysis of STX was realized.Finally,the standard sample recovery experiment was carried out in the homogenate of muscle tissue of Clam,which successfully proved the feasibility of this method in practical application.2.Au@SiO₂ NPs with controllable shell thickness were successfully prepared by the sodium silicate method,and Au@Si O₂ NPs two-dimensional SERS substrates were prepared according to the three-phase interfacial compression method.Au@Si O₂ NPs have shell isolation-enhanced Raman spectroscopic properties,and the shell thickness directly affects the SERS enhancement effect.Therefore,the changes of the SERS intensity corresponding to the shell thickness under different reaction times and different silicon source amounts are discussed respectively.The SERS enhancement corresponding to the shell thickness of 2～3nm is the best.A standard working curve was established according to the SERS intensity at the characteristic peaks of different concentrations of metronidazole,chloramphenicol,and capsaicin,and the recovery experiments in the corresponding river water samples were respectively detected.The results showed that the recoveries of all three were in the range of 95.30%to 108.79%,and the RSD was less than 6.48%.Furthermore,we assembled the Au@Si O₂ NPs prepared under the optimal conditions into a 2D SERS substrate,and demonstrated that the SERS enhancement of core-shell nanoparticles decreased linearly after 1%PVP wrapping on the surface of Au@Si O₂ NPs.The effects of different laser integration time,adding volume of Au@Si O₂ NPs,sodium borohydride etching time,and stacking layer number of monolayers on the SERS enhancement on the surface of 2D substrates were explored respectively.The Au@Si O₂ NPs monolayer still showed weak SERS enhancement when it was used to directly detect the hazardous substance metronidazole.When several layers are superimposed（three layers）,the SERS signal exhibits a small noise ratio,which limits its further application in complex environments.3.A bimolecular calibration aptamer sensor was designed,which was composed of Ag NMs@tetrodotoxin-aptamer（Ag NMs@Apt）NPs,Au@MBN@Ag@Compl--ementary（Au@MBN@Ag@Com NPs）NPs and tetrodotoxin.The SRES technology is based on this sensor to detect TTX in the muscle tissue of puffer fish.Au@MBN@Ag NPs were prepared with 4-mercaptobenzonitrile（MBN）as the internal standard and captured on the surface of Ag NMs by base-complementary pairing.In the presence of TTX,aptasensor was destroyed by the release of Au@MBN@Ag NPs@Com,resulting in the weakening of the I₂₂₂₈/I₅₂₀ ratio signal.Thus,the concentration of TTX was negatively correlated with SERS intensity of I₂₂₂₈/I₅₂₀.Finally,we successfully achieved highly sensitive detection of TTX in puffer fish muscle tissue samples by this method.