Microfluidic Tools for Cell Analysis
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Microfluidic technology is a powerful tool for spatial and temporal control of cellular environment to improve cell biological study. With surface chemistry, this platform can mimic complex biochemistries and geometries of extracellular matrix. Also, microchannels can precisely regulate transport of fluids and soluble factors. In this dissertation, we applied microfluidic systems for cell separation, controlling extracellular matrix properties, and regulating fluid environment. First, we studied cell separation using affinity chromatography columns. We monitored cell adhesion based on aptamer recognition of target cells. The sgc8 aptamers were coated on the capillary surface, which can capture target cells from a cell mixture with highly specificity. The aptamer capture was demonstrated to be strong by determining the number of bonds formed during aptamer capture and calculating the binding strength. The capture efficiency and purity were tested under different flow type: linear and oscillation flow. The oscillation ones showed better results in rare cell enrichment. Then, we selectively delivered reagents to captured cells through precisely controlling the fluidic environment. Hydrodynamic focusing can confine reagent stream in the middle of multiple fluidic streams. When passing these multiple laminar flow streams over the cell culture chamber, cells seeded under the reagent stream would be selectively treated. To avoid the damage of hydrodynamic shear stress to cultured cells, we build a two-layer microfluidic system. The system consisted of a cell culture chamber and fluid flow channel, which were located in different layers. The shear force was reduced from 6.0 dyn/cm2 in a one-layer device to 2.7 dyn/cm2 in the two-layer device. Three-dimensional scanning of fluid distribution using confocal microscope confirmed that boundaries between streams were well controlled. This approach demonstrated the capability of deliver reagent to different regions of the culture well at low shear stress. In addition, we engineered cell adhesion environment for high-throughput cell analysis. First, neutravidin arrays were patterned on the glass surface using microcontact printing, which helped control cell positioning. Next, multiple antibodies were conjugated to neutravidin spots by dropping them on different regions of surface. Those multiple antibodies could capture different cell types at different local points of a microchannel, which enabled parallel cell culture. Also, immobilized Fas antibody can capture cells, as well as, induce cell apoptosis. Therefore, multiple cell cues that guiding cell behavior were assembled in this device. Cell apoptosis study was achieved in a parallel way in this work.