Research On Signal Amplification Strategy Of Optical Fiber Localized Surface Plasmon Resonance

Optical fiber Localized Surface Plasmon Resonance(LSPR)sensing technology is a label-free detection technology,which has the advantages of high sensitivity,fast response and real-time detection,and is widely used in food safety,biomedicine and environmental monitoring and other fields.This thesis is based on the optical fiber sensor based on gold nanoparticles(Aunanoparticles,AuNPs),AuNPs polymers were successfully constructed by a two-step assembly method,and the catalytic precipitation effect of G quadruplexes was used to enhance the LSPR signal,realizing the detection of fumonisin B1(FB1),deoxynivalenol(DON)and mi R-103,and evaluation of the performance of the developed sensor,the specific research is summarized as follows:1.The method and application research of constructing AuNPs-based optical fiber LSPR FB1 sensor.Using Frens legally became AuNPs.The piranha solution was used to achieve the hydroxylation of the end face of the optical fiber,and the aminated optical fiber was obtained by treatment with 3-aminopropyltriethoxysilane(APTES).AuNPs were immobilized on the end face of the fiber through gold-hydrogen bonds,and finally the sulfhydryl-modified FB1 aptamer was coupled to the surface of AuNPs through gold-sulfur bonds to complete the preparation of the sensor.The optimal conditions for the preparation of optical fiber LSPR sensors were obtained:1%APTES treatment time 12 h,AuNPs modification time 10 h,10μM FB1 aptamer treatment 12 h.Under the conditions of 25°C,p H 7.5,and 12 h,after the FB1 aptamer specifically binds to FB1,the shift of the LSPR peak has a good linear relationship with the logarithmic concentration of FB1,and the detection range is 0.8-200 ng/m L,R~2=0.9817,and the limit of detection(LOD)was 0.17ng/m L.The sensor has good repeatability with a relative standard deviation(RSD)of 3.3%and good selectivity.The corn samples were used for detection,and the recovery rate of standard addition was between 96.08%and 112.23%,which verified the accuracy and reliability of the detection method.2.Construct AuNPs multimers on the end face of the optical fiber,construct nano-gap,and achieve the purpose of improving the sensitivity of the optical fiber LSPR sensor through the physical"hot spot effect".Firstly,AuNPs are coupled on the end face of the fiber,and then the AuNPs are bridged by pentaerythritol 3-mercaptopropionate(PETMP)to form AuNPs multimer with AuNP-(PETMP-AuNPs)n structure,and finally DON aptamer is modified to the end face of the fiber,to complete the construction of the sensor.The optimization results of sensor construction were as follows:1%APTES treatment for 12h,AuNPs first treatment for 5 h,4 mg/m L PETMP treatment for 3h,second AuNPs treatment for 5 min,and 15μM DON aptamer treatment for 12 h.Theoretical simulations show that there are a large number of"hot spot"structures in the AuNPs polymer,and the experimental results confirm that the LSPR redshift of the sensor is 3.4 times higher than that of the AuNPs monomer-based sensor,and the LOD is reduced to 1/8 times.The detection results of DON showed that the LSPR peak displacement had a good linear relationship(R~2=0.9934)with the logarithmic concentration of DON(0.05-200 ng/m L),LOD=0.04 ng/m L.The performance of the sensor was verified in the detection of corn samples.3.Adopt the dual signal amplification strategy of"hot spot effect"and HexSG4catalytic precipitation to improve the fiber LSPR signal.First prepare the AuNPs multimer structure on the end face of the fiber,and then construct the fiber optic LSPR sensor with mi R-103 probe molecule and the HexSG4 signal amplification element on the surface of the AuNPs,both of which can interact with the target molecule mi R-103 through their own recognition sequence.Complementary pairing.Under the catalysis of peroxidase by HexSG4,4-chloro-1-naphthol(4-CN)was catalyzed to form benzo-4-chlorohexadienone(4-CD),which was precipitated on the surface of AuNPs multimer,to amplify the signal.The ultra-sensitive detection of mi R-103 is achieved through the characteristic of the"hot spot effect"formed by AuNPs multimers that is highly sensitive to changes in the peripheral environment(4-CD)(signal secondary amplification).The preparation of the sensor mainly included the assembly of AuNPs multimers and the modification of the mi R-103 probe,and the optimal preparation process parameters were obtained through optimization.For 10~2-10~7f M mi R-103,the peak position shift of the fiber optic LSPR sensor has a good linear relationship with the logarithmic concentration of mi R-103,R~2=0.9912,LOD=6.4 f M,the sensor has a good linear relationship with mi R-21,mi R-155 and mi R-140 showed better anti-interference ability.The constructed three optical fiber LSPR sensors have realized the quantitative detection of FB1,DON and mi R-103.According to the methodology verification,the prepared sensors have the advantages of good selectivity,stability and specificity,and have a wide application prospect in the fields of food safety and disease diagnosis.Two strategies based on AuNPs multimer and catalytic deposition are proposed to enhance LSPR signal and sensor sensitivity,which provides a new idea for improving the performance of LSPR sensor.