The Research On UCNP-MOFs Fluorescent Aptamer Sensing Technology For Highly Sensitive Detection Of T-2 Toxin In Food

Recently,as the improvement of living quality,the Chinese government is more and more strict in the supervision of food safety.However,there are still hidden dangers of food safety.Mycotoxins in grains and other food products have the characteristics of wide distribution,stable properties,difficult to detect and serious harm.However,traditional large instruments or immunological methods cannot meet the increasing demand for detection.Therefore,the development of a highly sensitive and rapid detection method for mycotoxin is particularly important in dealing with food safety incidents and safeguarding people's health.In recent years,nanotechnology has developed rapidly and strengthened its integration with other fields.Due to the excellent luminescence properties of lanthanide metal elements,fluorescence sensing methods based on upconversion nanomaterials are favored.In addition,the metal-organic frameworks have a tunable pore size,large specific surface area,excellent adsorption capacity and efficient quenching capacity.Thus,it is imperative to use the advantages of the two materials to construct a new fluorescence sensing technology with high sensitivity detection.In this study,T-2 toxin was used as a typical representative of mycotoxins.For the main problems of cumbersome operation,low stability and insufficient sensitivity existing in the current detection methods,the controllable synthesis of up-conversion nanomaterials and metal-organic frameworks was explored,and the fluorescence aptamer probe was designed according to the fluorescence resonance energy transfer.Combined with the biotin-streptavidin amplification system,an efficient upconversion fluorescence aptamer sensing technology was constructed,which realized the highly sensitive detection of mycotoxins in food.Compared with the traditional fluorescence sensing technology,the advantages were highlighted.The specific research contents of this article are as follows:1.The controlled synthesis of upconversion nanoparticles(UCNPs)and metal-organic frameworks(MOFs).The controllable synthesis of UCNPs,MIL-101(Cr)and NH2-UiO-66 with different particle sizes was realized by solvothermal method and hydrothermal method.Firstly,UCNPs with different particle size and luminescence intensity were synthesized by solvothermal method by changing the growth time of crystal nucleus in the preparation process.The results were characterized by TEM and photoluminescence spectroscopy,and the optimal conditions for the synthesis of UCNPs with small particle size,good dispersibility and high fluorescence intensity were obtained.Then,by adjusting the volume of the mineralizer HF,MIL-101(Cr)with different particle sizes were prepared by hydrothermal method.The crystal form,light absorption properties,morphology and adsorption properties were researched in detail by way of XRD,FT-IR,SEM.The optimal synthesis conditions of MIL-101(Cr)with regular morphology,high crystallinity and large specific surface area were obtained.Finally,by using stable solvothermal method,NH₂-UiO-66 with different particle sizes was prepared by changing the volume of regulator acetic acid,and its characteristics were represented by XRD,FT-IR and SEM.The fluorescence quenching effect of NH₂-UiO-66 with different particle sizes on Cy3-modified aptamer(Cy3-aptamer)was investigated,and the synthesis conditions of NH₂-UiO-66 with high quenching efficiency were obtained.2.The research on Cy3-aptamer/MOFs fluorescent aptamer sensing technology for highly sensitive detection of T-2 toxin.A fluorescent aptamer sensing technology based on multiple energy transfer modes between Cy3-aptamer and NH2-UiO-66 was established to realize the highly sensitive detection of T-2toxin.NH₂-UiO-66 adsorbed Cy3-aptamer through hydrogen bonding,?-?interaction,and coordination,resulting in fluorescence quenching.The added T-2 toxin can recognize and bind with Cy3-aptamer,thus causing them to stay away from each other and.The recovery of intensity was positively proportional to the logarithmic concentration of T-2 toxin.Due to the high quenching efficiency of NH₂-UiO-66screened in the early stage and the excellent recognition ability of aptamer,the detection limit of T-2 toxin by the constructed fluorescence sensing method was as low as 0.239ng m L^-1(S/N=3).It not only presented a wide linear range(0.5?100 ng m L^-1),the excellent responsiveness,but also posed the specificity against other common toxins.In addition,this method can also effectively detect T-2 toxin in milk and beer,posing a good agreement with the detection results of national standard method(ELISA),so it provides a new method reference for rapid detection of food.However,traditional fluorescent dyes have some problems such as unstable fluorescence,poor environmental adaptability,and susceptibility to photobleaching,and the detection limit still ne EDX to be improved.Therefore,improving the stability and detection limit of fluorescent probes is worth further research.3.The research on Upconversion/MOFs fluorescent aptamer sensing technology for highly sensitive detection of T-2 toxin.A novel upconversion fluorescence aptamer sensing technology based on the fluorescence resonance energy transfer process between UCNPs and MIL-101(CR)was designed to realize the highly sensitive detection of T-2 toxin.In this research,the functional modification of UCNPs was performed while the surface potential was adjusted to avoid the irreversible process of mutual attraction between UCNPs and MIL-101(Cr)due to electrostatic interaction.The constructed upconversion nanoprobe(UCNPs-aptamer)combined with the biotin-streptavidin amplification system can not only induce fluorescence quenching by?-?interaction near MIL-101(Cr),but also respond more sensitively in the presence of T-2 toxin.With optimum,the linear range of this method is 0.1?100 ng m L^-1(S/N=3),and the LOD is 0.087 ng m L^-1.Compared with the fluorescence aptamer sensing technology of Cy3-aptamer/MOFs constructed in Chapter2,it performs lower detection limit and wider detection range.The method has very low response to OTA,FB1,AFB1,and ZEN,and has realized the detection of T-2 toxin in corn meal and beer samples,which presents it can be highly specific for the detection of real samples.This method provides reference for the point-of-care testing of contaminants in food,performing a certain application prospect for the analysis of protein,nucleic acid and biomarkers.