The Research On Upconversion Fluorescent Sensing Technology For Detection Of Several Mycotoxins

Objective The problem of food contamination caused by mycotoxins has become one of the most pressing problems in the world.Mycotoxins are secondary metabolites,which are produced by toxic fungi in suitable environments and can be found on the surface of cereals,feed,fruits,and herbs,as well as in food products such as cereals.The hazards of mycotoxins to humans include carcinogenic,teratogenic,neurotoxic,etc.,which are potential factors threatening people’s life safety.Fluorescence sensing technology based on upconversion nanoparticles has the outstanding advantages of simplicity,rapidity and sensitivity,and it is of practical significance to develop and design a new fluorescence sensing technology based on upconversion nanoparticles for the detection of mycotoxins in food.In this study,the common mycotoxins FB1,OTA and ZEN in foodstuffs were used as the research objects,and the upconversion nanoparticles were synthesized independently as fluorescent probes.The upconversion fluorescence sensing technology was developed.The research is as follows.Methods 1.Research on upconversion fluorescent aptamer sensing technology for highly sensitive detection of FB1 based on CHA.A new signal amplification strategy for the detection of FB1,the CHA reaction,was designed to combine the CHA reaction with the upconversion-graphene oxide system for the highly sensitive detection of FB1 in food by the response of fluorescence intensity.firstly,the aptamer of FB1 was assembled in magnetic microspheres using the streptavidin-biotin recognition,followed by the introduction of The aptamer was first immobilized on the surface of the synthetic magnetic microspheres using streptavidin-biotin recognition,and then the complementary chain of the aptamer was introduced to form the recognition element that specifically recognizes FB1.After the specific binding of FB1 to the aptamer,the complementary chain was detached from the recognition element by magnetic separation and acted as the initiating chain to cause the CHA reaction,which resulted in the detachment of the upconversion nanoparticles from the upconversion-graphene oxide system as the signal output element and expressed an intense fluorescence signal under 980 nm excitation light.Methods 2.Research on bi-color upconversion fluorescence sensing technique for simultaneously detecting OTA and ZEN.A bi-color upconversion fluorescence detection method for the simultaneous detection of OTA and ZEN in food was designed based on the fluorescence resonance energy transfer between upconversion nanoparticles and molybdenum disulfide nanosheets.The core-shell upconversion nanoparticles Na YF₄:Yb,Er@Na YF₄ and Na YF₄:Yb,Tm@Na YF₄ were synthesized to emit green and blue visible light under 980 nm excitation light,respectively,and the magnetic molybdenum disulfide nanosheets were synthesized as energy acceptors.two-color fluorescence resonance energy transfer system.In the presence of OTA and ZEN,the aptamer binds to the target to disrupt the energy transfer system,and then the magnetic separation further reduces the background signal interference,and the system exhibits two colors of fluorescence response under 980 nm excitation light.Results 1.Research on upconversion fluorescent aptamer sensing technique for highly sensitive detection of FB1 based on CHA:under optimal conditions,there was a good linear relationship between the logarithm of the FB1 concentration in the system and the fluorescence intensity ranging from 0.032 to 500 ng/m L,with a linear equation fit of F=163.8849lg C+405.5395（R²=0.9971）with a detection limit of 0.0121 ng/m L（S/N=3）.The sensitivity was ten times higher than the previously published detection method without signal amplification,and the spiked recoveries were 95.20-105.34%,99.79-103.20%,and 91.20-103.21%in corn flour,oat flour,and infant corn supplements,respectively,indicating that the sensor is suitable for accurate and sensitive detection of FB1 in real samples.Results 2.Research on bi-color upconversion fluorescence sensing technique for the simultaneous detection of ochratoxin A and zearalenone:under optimal detection conditions,the assay showed a good linear relationship between the logarithmic values of OTA and ZEN concentrations and the fluorescence intensity of the system in the range of 0.05-500 ng/m L（S/N=3）,and the experimentally obtained standard curves were F=1002.2905lg C+2084.7972（R²=0.9949）and F=503.5390lg C+1166.3405（R²=0.9972）,and the limits of detection were0.0397 ng/m L for OTA and 0.0311 ng/m L for ZEN with good specificity.Conclusions Among the current UCNPs,lanthanide-doped sodium fluoride has a wide range of applications in food detection,but its fluorescence self-quenching phenomenon due to surface defects can reduce its fluorescence intensity and thus lose a part of its fluorescence sensitivity.Based on overcoming this defect,this study conceived two options around how to enhance the detection sensitivity of lanthanide-doped sodium fluoride upconversion nanoparticles:First,through external auxiliary means,such as nucleic acid amplification signal amplification method,CHA reaction is introduced into the original upconversion fluorescence sensing system to give full play to the sensitivity of nucleic acid amplification and the stability of upconversion fluorescence,so as to achieve highly sensitive detection.Secondly,a rational nucleoshell structure was constructed by internal resynthesis method in the form of layer-by-layer assembly,which isolated the internal from the external environment and reduced the energy relaxation decay,thus reducing the generation of self-quenching phenomenon.Meanwhile,the prepared magnetic energy receptors can be easily detached from the system,which improves the signal-to-noise ratio of the sensing system.The results of this study showed that the above two schemes are feasible,and two new fluorescence sensing techniques were constructed to lead a highly sensitive detection of several typical mycotoxins,providing an effective technical reference for food safety supervision and rapid screening of hazards in China.