Research On Design And Performance Of LSPR-based Optical Fiber Biosensor

Optical Fiber Biosensors(OFBs)technology integrates a variety of disciplines such as physics,chemistry and biology,and has great potential in developing direct,sensitive,portable,cost-effective and real-time biosensors.Compared with electrochemical biosensors and other conventional sensing methods,OFBs have important applications in bioengineering,environmental monitoring,food hygiene detection,medicine and military field because of their higher flexibility and anti-electromagnetic interference ability.Although a large number of OFBs have been reported,it is still a challenge to develop OFBs with good stability,superior selectivity,excellent sensitivity and lower detection limit for rapid detection of target analytes.Recently,with the development of nanomaterials,Localized Surface Plasmon Resonance(LSPR)technology uses a small quantity of samples for detection and has made a great significant contribution to the development of smaller size and lower cost OFBs.The LSPR-based OFBs can developed after the noble metal nanoparticles(MNPs)functionalized with the corresponding ligands and fixed on the surface of the optical fiber.When the target analyte was combined with the ligands on the surface of the noble MNPs,the local refractive index(RI)can change,resulting in the change of LSPR resonance spectrum,so as to achieve the purpose of detection.OFBs based on LSPR have attracted much attention due to its advantages of label-free,high sensitivity and real-time detection.In this work,the mechanism of biosensors based on LSPR is deeply studied,and the application of LSPR in OFBs is demonstrated,which lays a theoretical and experimental foundation for the design of biosensors based on fiber optic LSPR.For this,a special property of tapered fiber structure in which evanescent field is much stronger in the tapered section has been used to develop the OFBs for glucose detection.Beam propagation method(BPM)has been used to simulate the tapered fiber structure to determine the energy distribution of the light propagating in the tapered region.Thereafter,gold nanoparticles(Au NPs)have been immobilized over a tapered section to increase the sensitivity and glucose oxidase(GOx)was functionalized over NPs-coated taper fiber to increase the selectivity of sensing probe.During measurement,the evanescent wave(EW)in the tapered section produces the LSPR phenomenon due to Au NPs over sensing probe.Moreover,RI changes after the interaction of GOx and glucose because it GOx reacts with glucose and produces hydrogen peroxide(H2O2).In addition,GOx also reduces the interference caused by other biomolecules in serum during detection.Thereafter,in other work,graphene oxide(GO)has been used along with Au NPs due to rich oxygen-containing functional groups of GO,which combined better with GOx on the surface of the tapered fiber to improve the biocompatibility of the sensing probe.For these purpose,the tapered fibers of diameters 40 ?m and 25 ?m have been fabricated using plasma technique based CMS machine,USA.10 nm-Au NPs and GO have been synthesized using Turkevich method and Hummer's method,respectively.The characterization of synthesized NPs and sensor probes were done using UV-Visible spectrophotometer,high-resolution transmission electron microscope(HR-TEM),scanning electron microscope(SEM),and energy-dispersive X-ray spectroscopy(EDX).Built a glucose sensing and detection system,and analyzed the performance of the designed sensor probe.The results prove that,it has been found that GOx/Au NPs/GO-tapered fiber sensor has a higher sensitivity and lower limit of detection(Lo D)over GOx/Au NPs-tapered fiber sensor.Further,reusability,reproducibility,stability and selectivity of proposed sensors have been also determined to show the usability of the sensors in the detection of glucose in human serum.