Research On Electrochemical Biosensor Based On Screen-printed Electrodes

Biosensor, since its concept was proposed, has obtained the high attention all over the world and maintained rapid development. It is an interdisciplinary area involving chemistry, materials, biology, physics, electronics and information technology. As a branch of biosensors, electrochemical biosensor can transfer the biological or chemical signal to electronic signal. And the signal output is converted to the forms of current, voltage, potential, conductance, electric quantity, and so on. With the development of integrate circuit and the appearance of low-cost and disposable screen-printed electrodes, electrochemical biosensors become miniature and portable gradually. Portable electrochemical biosensors, with its great potential to detect in-site and exchange information by wireless network, have broad prospects. Therefore, the research on electrochemical biosensor based on screen-printed electrode will expand the application of biosensors.This thesis researches on the fabrication of different kinds of screen-printed electrodes, the methods and principle of detection systems and the development of portable detection instrument. The content as follows:1. The fabrication of screen-printed electrodes. Various basically screen-printed electrodes were developed for different application purposes. Three kinds of electrodes, that is the single, double and three electrodes, the carbon, gold and platuminm electrode and the single and array electrodes, were prepared classified with composition, material and the numbers of working electrodes. Also, the fabrication process of all kinds of electrodes was introduced in detail and analyzed deeply.2. The fabrication of functional electrodes. In order to increase the function of screen-printed carbon electrodes, dopped mediator, dopped conductive materials and modified metal nanoparticles electrodes were developed though two different ways such as once printing or electrodeposition. These functional electrodes show strong ability of electron transfer, high conductivity and some metal electrodes performance. In this part, the fabrication process was introduced and the electrochemical behavior was studied.3. Direct electron transfer of horseradish peroxidase on porous structure of screen-printed electrode. Horseradish peroxidase is one kind of redox-oxidized enzyme of which ferric serves as the active center. Due to the porous structure characteristic of screen-printed carbon electrode, the enzyme can insert into the channel and its active center is close to the electrode. The direct electron transfer of horseradish peroxidase (Fe3+/Fe2+) was realized and the biosensor can be used for hydrogen peroxide detection.4. Direct electron transfer of myoglobin in mesoporous silica KIT-6 modified on the screen-printed electrode. Myoglobin is also one kind of redox-oxidized enzyme and ferric serves as its active center. KIT-6 consists of two interwoven mesoporous networks similar to that found in MCM-48 silica, but the pore in KIT-6 are much larger from 5 nm up to 12 nm. Myoglobin with the diameter of about 3nm can insert into the pore of KIT-6. By calculation of surface coverage of myoglobin, there is more than 3.5 times of myoglobin modified on the surface of electrode assisted by KIT-6 which makes the signal of direct electron transfer larger.5. Disposable amperometric xanthine oxidase biosensor used for the fish freshness detection based on screen-printed three-electrode system. Prussian blue, serving as mediator, was modified on screen-printed electrode by electrodeposition. Three-electrode and the corresponding socket were specially designed for this detection system. It realizes the detection of xanthine and hypoxanthine.6. The platinum nanoparticles modified screen-printed electrode for the detection of hydrogen peroxide and glucose. After the metal nanoparticles being electrodeposited on the screen-printed carbon electrode, the performance of the modified electrode is compatible to metal electrode. Platinum is a good catalyzer which can catalyze hydrogen peroxide directly. After the glucose oxidase being modified on the surface of electrode, the electrode also can catalyze glucose. In this part, the platinum nanoparticles modified screen-printed electrode can be used for hydrogen peroxide and glucose detection simultaneously.7. Disposable acetylcholinesterase biosensor based on screen-printed electrode for organic phosphorus pesticide detection. The inhibition mechanism of pesticide detection and the fabrication method of this biosensor were discussed. The disposable test strip was developed for pirimicarb detection.8. Prussian blue at carbon nanotube electrode for organic phosphorus pesticide detection. The Prussian blue at carbon nanotube material was once printed and the functional electrodes obtained can be produced in mass. This kind of Prussian blue electrode can be used for pesticide detection and the signal is stable. In addition, eight array electrodes were designed for the quick establishment of standard curve and simultaneous detection of eight samples.9. The design of portable hydrogen peroxide electrochemical biosensor. In this part, the single functional amperometic potentionsat for hydrogen peroxide detection was designed. The preparation of test strip, detection principle, the hardware and software of microprocessor, the circuit of amperometic potentionsat and the instrument operation were disscussed.