Study On Photoelectrochemical Sensors Based On Semiconductor Nanomaterials And Their Applications In Acetylcholinesterase Analysis

Biosensor is a kind of new technology associated with biology, chemistry, physics and electronics. Because it has advantages of high sensitivity, good selectivity, low cost and real-time determination, it has attracted interest and played an important role in food safety inspection, clinical diagnosis, chemical engineering and environmental monitoring. Owing to special size range, nanomaterials have many good properties which made them different from the macro and micro materials, such as large surface area, good biological compatibility and high catalytic activity. Moreover, with the development of photoelectrochemistry, the use of nanomaterials in photoelectrochemical sensors is a focusing study to improve the sensitivity.In this paper, we combined biosensors with nanomaterials such as semiconductor materials and composite materials to develop novel photoelectrochemical biosensors in research of acetylcholinesterase (AChE) activity. This dissertation includes four chapters.Chapter One. OverviewIn this chapter, a review related to principles and the development of biosensor was given. The characteristics of electrochemical enzyme biosensor were further introduced. Then, the development and applications of nanomaterials in biosensors were highlighted. We also briefly reviewed the current development of photoelectrochemistry, which include the concepts, working principles and applications in biosensor. Last but not least, we indicated the purpose and significance of the research as well.Chapter Two. Visible-light-actived photoelectrochemical biosensor for the study of acetylcholinesterase inhibition induced by endogenous neurotoxinsIn this chapter, a novel visible-light-actived photoelectrochemical biosensor was fabricated to study the inhibition of AChE activity induced by two endogenous neurotoxins,1(R)-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-Sal] and1(R),2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetra-hydroisoquinoline [(R)-NMSal] which have drawn much attention in the study of the pathogenesis of neurodegenerative diseases such as Parkinson’s disease. The photoelectrode was prepared by three steps as follows. At first, nitrogen and fluorine co-doped TiO2nanotubes (TNs) were obtained by anodic oxidation of Ti sheet. Secondly, silver nanoparticles (AgNPs) were deposited onto the TNs through microwave-assisted heating polyol (MAHP) process. At last, AChE was immobilized on the obtained photoelectrode and the biosensor was marked as AChE-Ag-N/F-TiO2. Due to the nitrogen and fluorine co-doping, the photoelectrochemical biosensors can produce high photocurrent under the visible light irradiation. Moreover, the presence of AgNPs greatly increased the photocurrent response of the biosensor. AChE-Ag-N/F-TiO2hybrid system was used to study AChE inhibition induced by (R)-Sal and (R)-NMSal and the result proved that both (R)-Sal and (R)-NMSal all exhibited mixed and reversible inhibition against AChE. This strategy is of great significance for the development of novel photoelectrochemical biosensors in the future.Chapter Three. Using metal-oxide semiconductor nanocomposites to structure a photoelectrochemical biosensor for the study of acetylcholinesterase inhibition induced by cadmium ionsWe report an investigation of a novel photoelectrochemical biosensor using N/F-TiO2labels cooperated with ZnO nanorodes for the inhibition of AChE activity induced by Cd2+, which has been considered to involve in the pathogenesis of Parkinson’s disease. First, the well-ordered TiO2nanotubes are fabricated by electrochemical anodic oxidation. Second, zinc oxide nanorodes (ZnO NRs) were deposited onto the TNs through cathodic deposition method. At last, AChE was immobilized on the obtained photoelectrode and the biosensor was marked as AChE-ZnO-N/F-TiO2. The effects of Cd2+ion on AChE activity in vitro was studied by using AChE-ZnO-N/F-TiO2hybrid system. Experimental results show that Cd2+ion exhibited dose-dependent and time-dependent effects on AChE. This strategy is of great significance for the development of novel photoelectrochemical biosensors in the future. Chapter Four. Clozapine regulation study with a novel photoelectrochemical biosensor based on TiO2cooperated with hyperbranched polyer hybridIn this chapter, we report an investigation of a novel photoelectrochemical biosensor using N/F-TiO2and hyperbranched polymer hybrid for the assay of clozapine influence on AChE activity. The photoelectrode was prepared by three steps as follows. First, nitrogen and fluorine co-doped TiO2nanotubes (TNs) were obtained by anodic oxidation of Ti sheet. Then, electrochemical polymerization method was exploited to modify the resulting nanotubes with polytyramine. Herein, we use gold colloids(GC) and thiol-functionalized hyperbranched azo-polymers (HBAP) via covalent bond as a platform which can facilitate the improvement of the photoelectrochemical performance of semiconductive nanomaterials. Moreover, the residue of polytyramine and Au nanoparticals were linked by covalent bond. After that, AChE was immobilized on the obtained photoelectrode and the biosensor was marked as AChE-GC-HBAP-tyr-N/F-TiO2. The designed photoelectrochemical biosensor displayed an excellent analytical performance with high sensitivity and stability.