Studies On The Reproducibility And Specificity Of Gold Nanoparticle Enhanced Optical Fiber Biosensor

Biosensing technology has advanced rapidly and dramatically in the last decadeand various highly sensitive sensing methods and devices are constantly emerging.However, high sensitivity also makes these devices vulnerable to nonspecificinterferences, which hindered the application process for biosensors. In thisdissertation, biconical optical fiber sensors were systematically studied in the aspectof sensing mechanism, manufacturing technology, sensitive enhancement, andlabeling technique. The underlying mechanism of poor reproducibility for biconicaloptical fiber sensors was revealed and several methods to enhance the sensitivity,reproducibility and specificity were proposed.(1) By combining the optical guiding property of optical micro/nanofibers andthe scattering and absorbance property of nanospheres, a model for calculating theoptical losses caused by nano spheres in the evanescent field of an optical fiber wasbuilt. Theoretical calculations suggested the possibility of single particle detection forgold nanoparticles, silver nanoparticles and bacterial using optical nanofibers. Singlegold nanoparticles of40were detected using a500nm thick nanofiber in experiments,which demonstrated the reliability of the model.(2) The underlying contradiction between sensitivity and reproducibility wererevealed through systematically experimental and simulation studies. The study shows that the high sensitivity is mainly caused by the modes coupling and this in turncaused the poor reusability of biconical fiber biosensors. This finding is of greatimportance for promoting the application process of highly sensitive optical fiberbiosensors.(3) The enhanced sensitivity of optical micro/nanofiber sensors modified withgold nanoparticles for refractive index detection and biodetection was carefullystudied both theoretically and experimentally. By introducing gold nanoparticles tothe surface of optical micro/nanofibers, the sensitivity and reproducibility can begreatly improved. A RI sensitivity of20A/RIU and detection limit of1pg/mL wasarchived in the experiments.(4) The selectivity enchantment of using gold nanoparticles as labels for opticalmicrofiber biosensors was evaluated. This sensor utilizes both the unique opticalproperty of ultrathin optical microfibers and the strong optical absorption property ofgold nanoparticles. Bio-functionalized gold nanoparticles are used as signal amplifiersin a sandwich assay to enhance both sensitivity and selectivity. In immunoassay, AFPwas detected in bovine serum with limits of detection of2ng/mL. This biosensor canbe regenerated for9times.