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UBC Theses and Dissertations

Concentration of bacterial pathogens using microfluidic dielectrophoresis systems Lin, Tao


Over the course of human history, people have been always troubled by unpredictable outbreaks of pathogenic bacteria. A rapid, specific and durable diagnostic sensor for detecting pathogens in a timely fashion is essential for identifying unknown infectious diseases and reacting by offering proper patient management and public health involvement without delay. Development of a microfluidic system incorporating interdigitated electrodes for characterizing concentration, purification and differentiation of pathogenic bacteria is presented. Polystyrene microspheres, Salmonella typhimurium, Campylobacter jejuni, Escherichia coli and Mycobacterium smegmatis are trapped by the positive dielectrophoretic force produced by the microelectrodes deposited and arrayed on a glass substrate covered with a PDMS microchannel. Diluted buffer used for producing positive dielectrophoresis for capturing cells is selected after evaluating the viability of the cells suspended in different buffers. Trapping efficiencies of Escherichia coli and Mycobacterium smegmatis are acquired by comparing input concentration and output concentration from plating results. Effective conductivities of both Escherichia coli and Mycobacterium smegmatis are calculated by obtaining optical density measurements corresponding to certain buffers with a range of different conductivity values used for trapping. Separation of a mixture with Escherichia coli and Mycobacterium smegmatis is achieved through the microconcentrator, although the results conflict with the calculated cellular conductivity values. The microfluidic DEP concentrator is shown to be an effective tool for studying and separating bacterial populations, and the results clearly indicate exciting directions for future work.

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