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Developments And Applications Of Electrochemical Biosensors

Posted on:2009-04-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:S H ZuoFull Text:PDF
GTID:1118360245998636Subject:Pharmaceutical Engineering and Technology
Abstract/Summary:PDF Full Text Request
As one branch of the newly emerging field known as bioelectronics, biosensor is an interdisciplinary area involved with biology, chemistry, material, physics, nanotechnology, microelectronics, information technology, etc. Biosensor has attracted extensive and lasting interest in both mechanism research of bioelectronic system and application development in the world. Electrochemical biosensor, one important member of the big biosensor family, is endowed with some obvious advantages in directly researching electron behavior during reaction involved with biological molecules and easily fabricating pocket biosensor devices, therefore, showing a more realizable model for actual application of biosensors. Main potential applications of biosensor include medical examination, environmental monitoring, food security monitoring and application for national security.This paper aims at establishing the whole method for electrochemical biosensor development, including fabrication of basic electrode, modification of electrode, immobilization of biological molecules, electrochemical measurement and development of pocket electrochemical instrument. Both mechanism research and application exploitation are involved in the work, which will be described in detail below:1. Fabrication of basic electrodes. Planar carbon electrodes were fabricated through manual screen-printed technique and were used as the basic electrodes for the most biosensors described in our work. The surface characteristics of screen-printed electrodes (SPEs) were investigated and the activation pretreatment of SPEs was studied. SPEs could be mass-produced at low cost, holding more application value than commonly used metal or glass carbon electrodes. In addition, carbon paste electrodes were fabricated and their electrochemical behaviors were investigated.2. Study on methods for immobilization of biological molecules and electron-transfer mediators. Several enzyme immobilization methods were developed including sol-gel encapsulation, chitosan-Glutaraldehyde crosslinking, etc. Some electrochemical substances including Prussian Blue (PB), Ferrocene (Fc) and its derivatives, potassium ferricyanide and Methylene Blue (MB) were used as electron-transfer mediators of which the characteristics were investigated. The effect of silver nanoparticles on enhancement of biosensor performance was also studied.3. Construction of hydrogen peroxide sensor based on Prussian Blue modified screen-printed electrode. Known as"artificial peroxidase", PB is selective electrocatalyst for hydrogen peroxide reduction, thus PB can be used as a transducer for hydrogen peroxide detection through electrodeposition of PB on SPE. The measurement conditions of the sensor were optimized and performance parameters were obtained. The proposed biosensor could be fabricated using a simple, low-cost strategy, which provided an alternative tool for hydrogen peroxide detection in a cheap, fast and accurate way.4. Three types of glucose oxidase (GOx) biosensors were fabricated through immobilization of GOx on PB modified SPEs. These biosensors could work at a low working potential of -0.05V, so interference from electrochemically active substances. Silver nanoparticles were used to enhance the performance of the biosensors. Research on the fabrication technology and reproducibility of the SPE-based GOx biosensors were performed, which were important for mass-production of the biosensor.5. An acetylcholine esterase biosensor based on PB modified SPE was fabricated for detection of acetylthiocholine. The proposed biosensor could be developed to fast detect organophosphate residues.6. Direct electrochemistry of GOx and xanthine oxidase (XOD) was investigated respectively on SPEs for the first time. Experiment conditions were optimized and discussed in order to obtain direct electron transfer between the enzymes molecules and the SPEs, which was significant for fabrication of the so-called"third generation biosensor"without mediators. Actually, two types of mediatorless GOx biosensor were fabricated for glucose detection in the work.7. Two types of DNA biosensors were fabricated for detection of DNA hybridization reaction, which were respectively based on zirconia doped carbon paste electrodes and zirconia modified SPEs. An effective and simple method was used to immobilized probe DNA on electrode surfaces through affinity between zirconia and phosphate group. It's significant to use the proposed renewable carbon paste electrode or disposable SPE for DNA biosensor, since one new DNA biosensor is usually used once.8. A design scheme for a miniaturized potentiostat using MSP430 as microprocessor was proposed. Compared to bench electrochemical workstation, the proposed potentiostat is much smaller and cheaper. Three electrochemistry methods including cyclic voltammetry, current-time amperometry and differential pulse voltammetry can be performed on this potentiostat. With interface with SPEs, the miniaturized potentiostat will meet the requirement of electrochemical measurement using the enzyme or DNA biosensors fabricated in this work.
Keywords/Search Tags:Electrochemical enzyme biosensor, Electrochemical DNA biosensor, Screen-printed electrode, Direct electron transfer, Potentiostat
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