Study Of Surface Functionalization Of Fiber Optic Biosensors For The Detection Of Streptavidin

Due to their small size,anti-electromagnetic interference,high sensitivity and specificity,fiber optic biosensors(FOBs)have been widely employed in the field of biological applications.One important preparation step for FOBs is the surface functionalization of the fiber that was presented using two methods in this paper to immobilize the biological sensing elements.One is the electrostatic layer-by-layer assemble(ELBL)and the other is the covalent binding utilizing(3-aminopropyl)triethoxysilane(APTES).We proposed three FOBs to detect streptavidin.The main contents are described as follow:1.Development trend and application of biosensors were introduced,FOBs were classified and systematically stated,our desired fiber surface functionalization of materials and surface modification process were analyzed,and biotin-streptavidin application was outlined.2.The theory of Fresnel reflection and Mach-Zehnder interferometer(MZI)was introduced and experimentally demonstrated.Fresnel reflection based sensor's refractive index(RI)performance was calculated that the theoretical and experimental values are nearly the same in low range of refractive indices.Through model simulation by Rsoft software and experimental verification of RI,the MZI based sensor was presented that the higher the RI,the greater sensitivity.Those put a solid foundation on the following biological testing.3.A Fresnel reflection based FOB using ELBL technology was proposed.Different bilayers of poly dimethyl diallyl ammonium chloride(PDDA)with polycation and poly(sodium-p-styrenesulfonate)(PSS)with polyanion were modified to immobilize the biotin for sake of the detection of various concentrations of streptavidin solutions.The optimal number of bilayers was five through experimental analysis,and the reproducibility and selectivity of the sensor was also verified.4.A FOB using APTES as a silane coupling agent to immobilize the NHS-biotin based on Fresnel reflection was proposed.The selectivity was measured,and the practicability was particularly demonstrated utilizing a more representative protein immunoglobulin G.5.A label-free FOB based on thin-core modal interferometer was proposed.The MZI based sensor was two bilayers of(PDDA+PSS)modification.We chose the Hill model for explanation of the binding capability of biotin-streptavidin system.The selectivity was also measured.It shows that the detection limit can be improved through optimizing the structure of fiber sensors.