Construction And Application Of Optical Fiber Localized Surface Plasmon Resonance Aptamer Biosensor

With the development of the economy and the improvement of living standards,people pay more attention to food safety issues.Harmful ingredients in food,such as zearalenone(ZEN),heavy metal lead ions(Pb²⁺),T-2 toxin,etc.,have seriously harmed consumers'lives and health.Therefore,it is very important to develop a fast,convenient,and real-time method for detecting harmful ingredients in food.Traditional detection methods,high-performance liquid chromatography(HPLC)and gas chromatography(GC)have many disadvantages of high cost and long time,which cannot meet the requirements of rapid detection.The optical fiber localized surface plasmon resonance(LSPR)aptamer sensor has the advantages of small size,high sensitivity,and high detection accuracy,which has great prospects in food safety and biological detection.Therefore,this thesis has developed a portable,low-cost,and reusable optical fiber LSPR aptamer biosensor for the detection of ZEN,Pb²⁺,and T-2 toxins in food.(1)According to the Frens method(sodium citrate reduction method),gold nanoparticles(Au NPs)were synthesized.The particle size of Au NPs was determined to be about 25 nm by transmission electron microscopy.Piranhas solution was used to hydroxylate the optical fiber sensor,and 3-mercaptopropyl trimethoxy silane(MPTMS)was used to obtain the mercaptoylated optical fiber sensor.Au NPs were fixed on the sensor of the optical fiber sensor by forming the gold-sulfur bond(Au-S).The scanning electron microscope showed that the Au NPs were uniformly distributed on the sensor of the optical fiber sensor with consistent particle size.Finally,by forming Au-S,the mercapto modified ZEN aptamer was fixed on the sensor of the optical fiber sensor to complete the construction of the sensor.The optimal conditions for the construction of fiber optic LSPR sensor were as follows:2.0%MPTMS,Au NPs modification time 12h,p H 8.0,and 10?M ZEN aptamer.The results showed that there was a good linear relationship between the LSPR peak shift values and the logarithmic concentration of ZEN(1.0 ng/m L?480.0 ng/m L),R²=0.9836,and the detection limit was 0.102 ng/m L.Also,the sensor has good repeatability(RSD=2.8%).It can effectively avoid ochratoxin A,vomitoxin,and T-2 toxin interference,which demonstrated it has excellent selectivity.The recovery rate was between 85.0%and 102.0%,which indicated that the sensor could be used to detect ZEN in actual samples.(2)The construction of optical fiber LSPR sensor for Pb²⁺detection was carried out according to the above methods.The optimal conditions of sensor construction were as follows:MPTMS concentration2.0%,Au NPs modification time 12 h,p H 7.5,Pb²⁺aptamer concentration 5.0?M.The results showed that the logarithmic concentration of Pb²⁺(0.2 ng/m L?625.0 ng/m L)showed a good linear relationship with the LSPR peak offset(R²=0.981)and the detection limit was as low as 0.03 ng/m L.The sensor has good repeatability(RSD=3.9%).It has good selectivity,showing a strong anti-interference ability to mercury ions,cadmium ions,and iron ions.The recoveries of Pb²⁺in drinking water were between 93.6%and 101.9%,which verified the feasibility of detecting Pb²⁺in actual samples(3)The Graphene oxide(GO)/gold nanoparticles(GO/Au NPs)composites were prepared by in-situ formation of Au NPs on the GO surface.The transmission electron microscopy showed that the Au NPs on the GO/Au NPs composites were uniformly dispersed on the GO surface with a particle size of about 20nm.The GO/Au NPs composite material was dropped on the sensor of the optical fiber sensor,and it was fixed on the sensor of the sensor by physical adsorption.The scanning electron microscope showed that the GO/Au NPs composite material was successfully adsorbed on the sensor of the optical fiber sensor.The amount of Au NPs on the GO surface was reasonable and evenly dispersed.The mercapto-modified aptamer was fixed on the sensor of the sensor by forming Au-S.The optimal conditions of sensor construction were obtained as follows:the drop coating amount of GO/Au NPs material 40.0?L,1.0?M T-2 toxin aptamer.The sensor was applied to detect the T-2 toxin solution,and the results showed that the shift of LSPR peaks an excellent linear relationship with the logarithmic concentration of T-2 toxin(0.5ng/m L?1000.0 ng/m L)(R²=0.9875),and the detection limit was 0.249 ng/m L.Also,the sensor showed a strong anti-interference to ZEN,Ochratoxin A,Vomitoxin,and Aflatoxin,which demonstrated that it had good selectivity.The recovery rate was between 89.3%and 95.7%when it was used to detect barley tea,through which the reliability was verified.The fiber optic LSPR biosensor constructed in this thesis has realized the quantitative detection of ZEN,Pb^2+,and T-2 toxin in food.It has the advantages of a wide detection range,low detection limit,and strong selectivity.It has excellent application prospects in food safety detection and biological detection.