Applications of micro-3D printing to microfluidic cell dosing



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Cellular growth, development, differentiation, and death are mediated to some degree by the interaction of soluble factors with plasma membrane receptors. Traditionally the cellular response to chemical cues has been studied by exposing entire culture dishes to a desired reagent. While the addition of soluble reagents homogenously to cell culture dishes provides a basis for understanding much of cell biology, greater spatial resolution of reagent delivery is necessary in order to elucidate mechanisms on the subcellular scale. This dissertation explores techniques that may improve the quality and precision of delivering soluble factors to cultured cells in order to better understand the complex processes of cell biology. These advancements were made possible by applying high intensity, focused laser light to soluble materials to achieve microscopic three-dimensional (µ-3D) printing. In combination with a previously developed microfluidic cell dosing platform, microstructures were designed and µ-3D printed to hydrodynamically focus reagent streams for cell dosing. Structures were also µ-3D printed within micrometers of living cells from a solution of gelatin and bovine serum albumin with minimal cytotoxicity. When µ-3D printed, these proteins displayed both temperature and pH-responsive properties. In order to allow for on-the-fly control of reagent stream size and temporal pulse width, microstructures were µ-3D printed from temperature-responsive N- isoproplyacrylamide. To further improve the temporal resolution of the system, a technique for cycling between reagents with millisecond exchange times using laminar flow microfluidics was developed. The utility of these techniques was demonstrated by staining rat Schwann cells and mouse neuroblastoma rat glioma hybrid cells (NG108-15) with focused streams of fluorescent dyes. These advancements may allow future experiments to determine the placement of soluble factors necessary for bacterial quorum sensing or stem cell differentiation.