Development of microfluidic devices for cell based analysis
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The field of microfluidics has emerged as an important platform for cell biology research. This dissertation focuses on method development of cell separation and cell culture using microfluidic devices. Four detailed studies were presented. The world-to-chip interface is an important aspect of microfluidic devices. A unique phenomenon for vertical inlets of microfluidic affinity chromatography devices was reported. Cell capture density that was 5-10 times higher was found near the vertical inlet region compared with downstream of this device. The enhanced capture increases the possibil-ities of nonspecific binding, resulting in the deterioration of overall separation purity. However, the enhanced capture efficiency at vertical inlet regions holds the potential for negative enrichment devices, since negative enrichment is difficult to achieve using straight channel devices due to the low capture efficiency. We designed a multi vertical inlet device to utilize the inlet effect for negative enrichment. Target cells were sepa-rated with >90% purity by depleting unwanted cells on an antibody coated surface using this device. Controlling surface coating patterns is another important aspect of microfluidic cell affinity chromatography. Multi parameter analysis can be achieved by immobilizing multiple antibodies in well-defined regions. We proposed the application of pneumatic valves to the surface coating patterns. Up to four antibodies were coated in one straight channel with defined boundaries. Multiple cell line capture can be achieved conven-iently by a flowing cell mixture through the main separation channel continuously. On-chip cell culture was studied with novel cell seeding approach. We employed multilayer soft lithography to fabricate vacuum control channel. Cells can be loaded into dead-end side channels without the disruption fluidic channels via vacuum actuated cell seeding. The filling of 256 side channels required only a single vacuum activation, reducing time and labor costs. Because it is an active seeding strategy, multiple cell lines can be loaded into one chip using sequential injection. Two cell lines were simul-taneously cultured for four days in one device with >90% viability, which is comparable to cultures in petri dish. Cell proliferation at each side channels can also be tracked. This device is also amenable for long-term cell based assay with selective chemical treatment.