Researches On Microfabricated Electrochemical Cell-Based Biosensors For Biochemical Paramet-ers Detection

Living cells can respond to external stimuli, such as drugs and environmental change, or receptor functions. This induces the functional change of cell metabolism and variations in biochemical parameters, which can be detected using micro fabricated electrochemical biosensors. Cells are generally cultured on the sensor surface, and the extracellular electrolyte together with the sensor form a micro electrochemical cell, thus the biochemical parameter change induced by the physiological state of cells can be output as a physical electric signal through the transformation of transducers. By doing this, the quantitative detection and analysis in cellular level can be realized. The miniaturization of sensors and the cell-chip coupling are the key issues. In view of this the micro-electromechanical systems (MEMS) technologies are widely applied in the construction of cell-based biosensor, such as microelectrode array (MEA), interdigitated electrodes (IDE) and field effect transistor (FET). With good biocompatibility, these cell-based biosensors have been widely studied and preliminary applications have been achieved in drug screening, and environmental monitoring.Based on the important techniques in the sensor design and fabrication, the electrolyte/metal-insulator-silicon (EIS/MIS) structured sensor, gold microelectrode and carbon microelectrode have been studied in this thesis. Good coupling of primary kidney cells on the EIS/MIS sensor surface are demonstrated in vitro, and the detection of cells acidification rate, the extracellular redox potential (ERP) are successfully realized. The MIS sensor can also be applied for the construction of potentiometric glucose sensor with high sensitivity, which expands the applications of MIS sensor in biology. Besides, the carbon micro-electromechanical systems (C-MEMS) technology is successfully used for the fabrication of carbon microelectrode, which facilitates the miniaturization of carbon electrode. Then the carbon microelectrode is applied for insulin detection, which provides a new potential, feasible way for the study of exocytosis. The major contents and contributions of this thesis are given as follows:1. A new effective method for ERP detection is studiedThe ERP value, which reflects the redox state of extracellular environment, has close relationship with cell proliferation, differentiation, apoptosis and cancer erosion. Based on the MIS sensor and the micro chamber with flow injection system, this thesis provides a feasible solution for ERP detection without addition of other redox mediators. It is found that the mitochondrial electron transport chain has important effect on ERP detection.2. An integrated sensor for simultaneous detection of acidification rate and ERP is demonstrated to be feasibleThis thesis proposes an integrated sensor design for the simultaneous detection of the two parameters. The integrated sensor has comparable performance with separate EIS or MIS sensor. The study of the two parameters under physiological state is primarily carried out, which demonstrates the feasibility of the sensor design. This design has potential application in revealing the cell metabolism mechanism and drug analysis and testing.3. A new type potentiometric glucose sensor with high sensitivity is developedAn ultra thin polypyrrole-glucose oxidase (PPy-GOD) film is modified on the MIS sensor surface, and much higher sensitivity for glucose detection is obtained in comparison with other types of sensor with the same PPy-GOD film. The application of photovoltage technology and the micro chamber with flow injection system, contribute to the improved sensor sensitivity and response time.4. Carbon microelectrode fabricated with C-MEMS technology is applied for insulin detectionThe carbon microelectrode fabricated through the pyrolysis of photoresist with C-MEMS technology has good electrochemical performance. After electrodeposition of nano RuOx particles on the carbon surface, insulin oxidation is electro-catalyzed and its electrochemical detection is achieved. This is the first application of C-MEMS technology for insulin detection after glassy carbon, carbon paste and carbon fiber electrode. C-MEMS technology has the advantages of flexible design of the electrode structure and dimensions, which is propitious to the miniaturization and integration of insulin sensor.