Research On Brucellosis Sensor Based On Dispersion Turning Point Long Period Fiber Grating

In recent decades,due to the unique optical properties of optical fiber,it has become a research hotspot in biomedicine,physical sensing,optoelectronic devices and other fields.In particular,label-free biochemical sensors based on fiber gratings have been widely studied by scholars.The laber-free biochemical sensor based on long-period fiber grating（LPFG）has the advantages of small size,low cost,label-free,good flexibility,uncharged safety,and it has a strong anti-electromagnetic interference capability,as well as the external environment is more sensitive to changes in the refractive index,etc.With unique advantages and value of research in the field of label-free detection of biomolecules.This article uses LPFG and dispersion turning point long-period fiber gratings（DTP-LPFG）as Carrier,combined with the advantages of graphene oxide（GO）which has good biocompatibility and abundant oxygen-containing functional groups.as well as the local surface plasmon resonance（LSPR）effect of Ag nanoparticles（Ag NPs）,the graphene oxide encapsulated silver nanoparticle（EGO-Ag NPs）composite material is constructed by the method of electrostatic combination of GO and Ag NPs.EGO-Ag NPs composite material also has the advantages of controlling the distance between particles,preventing aggregation,enhancing the stability of nanoparticles,and preventing the oxidation of Ag NPs.Further modify the surface of the sensor to improve the refractive index sensitivity,EGO-Ag NPs integrated LPFG and EGO-Ag NPs integrated DTP-LPFG Brucellosis immunosensor was prepared.The main research content and research results of the thesis are as follows:（1）Explain the coupling mode theory of LPFG and DTP-LPFG in detail,and analyze the characteristics of the sensing principle based on the phase matching conditions and mode coupling principle of LPFG and DTP-LPFG.LSPR mechanism for enhanced sensing performance LPFG and DTP-LPFG theoretical analysis,and the structure of LPFG and DTP-LPFG biosensor and the mechanism of surface molecule binding are described,which lays a theoretical foundation for subsequent experiments.（2）Manufacture an immunosensor based on EGO-Ag NPs integrated LPFG,and use it for the detection of brucellosis.the detailed steps are:The EGO-Ag NPs are fixed on the surface of DTP-LPFG by covalent bonding,and the sensor was hydroxylated,silanized,and modified EGO-Ag NPs composite materials to form an EGO-Ag NPs integrated LPFG sensor,and explored EGO-Ag NPs integrated LPFG sensor refractive index（RI）sensitivity;Then use brucellosis antigen molecules to covalently bond to the surface of LPFG and act as biological receptors;Next use the biosensor prepared above to complete the detection of brucellosis antibody molecules with different concentration gradients;Finally,a specific control experiment was performed on the EGO-Ag NPs integrated LPFG immunosensor..The experimental results show that the RI sensitivity of the LPFG sensor modified with EGO-Ag NPs composite material is～20.12 nm/RIU,which is 29.3%higher than that of the bare LPFG;the detection limit of the biosensor is～10 pg/m L,and the detection sensitivity is～0.184 nm/log（pg/m L）,the detection saturation point is～1μg/m L;and the Brucellosis immunoassay process conforms to the Langmuir model,and the dissociation coefficient of the EGO-Ag NPs integrated LPFG biosensor can be obtained by using this model to be～3.396×10^-9 M,the affinity coefficient is～2.94×108 M^-1;（3）Manufacture an immunosensor based on EGO-Ag NPs integrated DTP-LPFG,and use it for the detection of brucellosis,the detailed steps are:fix EGO-Ag NPs on the surface of DTP-LPFG by covalent bond to form a new type of fiber grating sensor This sensor has the advantages of DTP-LPFG bimodal effect and nano-silver LSPR effect.At the same time,it utilizes the good biocompatibility of GO and is more sensitive to changes in external RI;Explore the RI sensitivity of the EGO-Ag NPs integrated DTP-LPFG sensor;then,use the brucellosis antigen molecule as a biological receptor,and use the biosensor prepared above to complete the detection of brucellosis antibody molecules with different concentration gradients.The experimental results show that the RI sensitivity of the DTP-LPFG sensor modified with EGO-Ag NPs composite material is～-294.53nm/RIU,～638.41 nm/RIU,and～932.94 nm/RIU for the short-wave resonant wavelength,long-wave resonant wavelength,and resonant double-peak spacing,respectively,which is 16%,33%,27%higher than the RI sensitivity of bare DTP-LPFG;The detection limit of the biosensor is less than 100 pg/m L,the detection sensitivity is～0.645 nm/log（pg/m L）,and the detection saturation point is～10μg/m L;The Langmuir model can be used to obtain the dissociation coefficient K_d of the EGO-Ag NPs integrated DTP-LPFG biosensor is～6.271×10^-9 M,and the affinity coefficient K_a is～1.595×10⁸ M^-1;the use of Brucellosis affected bovine serum and other solutions for clinical specific control tests prove that the sensor has a high degree of influence on the entire Brucellosis Specificity,its detection performance is similar to that of detection in a pure environment,thus confirming its certain potential in clinical applications.Experiments have proved that the low-titer OMP16 protein Brucellosis is used for immunoassay.Due to the unique advantages of the integrated DTP-LPFG sensor based on EGO-Ag NPs,it still has good detection performance in the immunoassay process.