Development Of Electrochemical Biosensors Based On The Incorporation Of Poly(thionine) And Hybrid Nanomaterials

Recent years witness increasing interests of developing direct or reagentless electrochemical enzyme sensors, most known as the third generation enzyme sensors,and highly sensitive electrochemical biosensors. Successful mediated biosensors have been fabricated with enzymes either chemically modified with the electron relays or tethered to the mediating redox polymers modified on the electrodes. However, some redox mediators in use may suffer from low electron transfer efficiency or part solubility causing the gradual leaking of mediators during continuous sample analysis. With the rapid development of nanostructured materials and nanotechniques, many nanomaterials with unique physical and chemical properties have been increasingly explored for electrocatalytic sensing applications. Nanoparticles such as gold particles (GNP) are recognized as a kind of potential nanomaterials that may allow for electron transfer between the anchored enzyme and the electrode facilitating the direct electrochemical analysis. In particular, GNP can show a high affinity to a wide range of biomolecules and chemical ligands, which may offer an ideal microenvironment for these entities to be bound with high bio- or electro-activities. Carbon nanotubes (CNT) represent another important group of nanomaterials that offer the exciting possibilities of developing novel electrochemical biosensors due to their special properties of promoting electron-shuttling reactions with electroactive species (i.e., enzymes). Moreover, some pioneering studies have recently focused on the development of the CNT-based sensors by integration of CNT with other materials including conducting polymers, redox mediators and metal nanoparticles. Additionally, the amplified electronic transduction of antigen/antibody process is of importance in the development of a highly sensitive immunosensor. In this thesis, firstly, a novel direct electrochemical sensing platform has been designed by covalent incorporation of carbon nanotubes (CNT) and gold nanoparticles (GNP) onto the poly(thionine) (PTH) film that was deposited on the glass carbon electrode (GCE) by electropolymerization, which has been utilized for the fabrications of an enzyme sensor and an immunosensor(Chapter 2, 3); secondly, a highly sensitive impedance immunosensor has been developed by combining the Biotin-Avidin System (BAS) with a peroxidase-catalyzed precipitation method(Chapter 4). The details are summarized as follows:(1) In Chapter 2, a PTH film-based enzyme sensor has been fabricated the electrochemical sensing platform using CNT and GNP. With the synergic effects of the composite nanomaterials together with the excellent mediating redox polymer, the proposed PTH-CNT-GNP platform was characterized to allow faster electron transfer and higher...