Studies On Magnetic Nanoparticles Labeled Optical Nanofiber Biosensors

Compared with other kinds of biosensors, Optical fiber evanescent wave sensoris a powerful biochemical detection method with advantages of high sensitivity,compact structure, low cost, fast responding, ability to work under extremecircumstance and great potential for array sensing and multi-target detection.During the past decades, researchers have made progress in aspects such aspropagating theory in biconical nanofiber, fabrication methods and its application.However, there are still problems have to be solved before this powerful biosensor istransformed from lab research to practical use. Now the main problems lie in themass production of biconical fiber with very high consistency and improvedperformance in complicated sample detection. In this dissertation, biconical opticalnanofiber was systematically studied in aspects of sensing mechanism,manufacturing technology, sensitivity enhancement and labeling technique, aimed atsolving those problems and promoting the practical use of optical nanofiberbiosensors.1) The transmission properties, mode characteristics and loss mechanism ofbiconical optical fiber were studied. Factors contribute to the reproducibility ofbiconical optical fiber were analyzed and simulated using FD-BMP method. It’sproposed that adiabatic biconical optical fiber can be one way to solve thereproducibility of biconical optical fiber sensor. A simple version of fiber tapering system was set up. The way how geometric profile and transmission loss of opticalnanofiber functioned with fabrication parameters such as the flow of hydrogen andpulling speed, was studied. Adiabatic biconical optical fibers with highconsistency were fabricated using heat-drawing method.2) The as-made biconical optical fiber demonstrated low sensitivity throughlower index(RI) section, supposing that it’s reasonable to solve reproducibility withadiabatic biconical optical fiber. High absorbance sensitivity of1×10-9mol/L wasachieved by MB (Methylene Blue) detection. Label-free detection sensitivity is100pg/ml when avindin and biotion were used.3) To improve the sensitivity and selectivity of optical fiber biosensor whendealing with complicated samples, a new detection method was proposed by usingmagnetic nanoparticles both as pre-preparation means and signal amplifying label.High sensitivity of optical nanofiber to magnetic nanoparticle adsorption wastheoretically studied. And single MNP with diameter of200-300nm wassuccessfully resolved by optical nanofiber biosensor with a diameter of380nm.In this dissertation, adiabatic biconical optical nanofibers were fabricated usingheat-drawing method. Strong sensitivity enhancement ability of magneticnanoparticles was illustrated both theoretically and experimentally. The biosensorproposed is high sensitive, highly selective, low cost, compact, and immune toelectro-magnetic disturbance. It’s designed for high sensitivity and selectivitydetection in complicated samples, such as human serum. It has great potential forpractical use in clinical diagnosis, food safety, environment monitoring and homedefence.