Manufacturing of conductive nanofibers by various methods and development of amperometric biosensors

Biosensors are analytical devices that convert a biological response into a signal and are widely used in the determination of substances that have effects on human health, such as glucose and phenolic substances. Biosensors are generally prepared by immobilizing bioreceptors in polymer film matrices and increasing the interaction between the bioreceptor and the analyte also increases the biosensor performance. Recently, the development of conducting nanofibers and their utilization in sensors has drawn attention due to their remarkable physical and electrochemical features acquired by their wide surface area. Among conducting polymers poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) are widely used in biosensor applications due to their high conductivity and their ability to create thin films. In this thesis, we aimed to obtain PEDOT and PPy nanofibers and to utilize them in biosensors. Here in, it is intended to increase the interaction between the bioreceptors and the analyte by providing large immobilization areas due to the highly porous structure of the nanofibers, and thus, the conductive nanofiber-based biosensors have high sensitivity, low detection limit (LOD) and short response time. Low-cost and simple methods have been preferred for the fabrication of PEDOT and PPy nanofiber-based biosensors. Conductive nanofibers were produced by chemical vapor polymerization of EDOT and pyrrole on polyacrylonitrile and polyacrylonitrile/multi-walled carbon nanotube (MWCNT) nanofiber mats prepared by electrospinning method. Nanofibers were characterized by SEM, FTIR, cyclic voltammetry methods. Amperometric glucose and polyphenol biosensors were designed by immobilization of glucose oxidase and polyphenol oxidase on the nanofibers via glutaraldehyde and the analytical performances of the biosensors were evaluated. In these studies, the effect of various factors such as amount of enzyme , effect of MWCNT, and change of tracked component on the analytical performance of biosensors were investigated. Sensitivity, linear range, LOD, Km and Imax values were determined for each biosensor and the stability of all biosensors was investigated. In addition, shelf life and real sample analyzes were achieved for some of the biosensors. While performing real sample analysis, glucose biosensors were used for glucose determination in fruit juice, and polyphenol biosensors were used for catechol determination in tap water and industrial water. In studies where the oxidation of H2O2, is followed; it was found that PEDOT-MWCNT-NFs/GOx-2 and Pt/PPy-MWCNT-NFs/GOx-1 have highest sensitivity (92.24 and 81.74 µA/mM.cm2), low LOD (7.7 and 2.4 µM), and low Km (2.21 mM and 1.13 mM), they were selected as the best performing biosensors among the PEDOT and PPy nanofiber-based glucose biosensors. When polyphenol biosensors are examined, Pt/PEDOT-MWCNT-NFs/PPO-2 and Pt/PPy-MWCNT-NFs/PPO-2 have high sensitivity (7042.2 and 10015 µA/mM.cm2 ), low LOD (0.114 and 0.404 µM ) and low Km (0.007 mM and 0.013 mM), they were selected as the best performing biosensors among PEDOT and PPy nanofiber-based polyphenol biosensors. Examination of nanofiber-based biosensor created in this thesis demonstrates that the performance of sensors was found to be better than most studies in the literature.