Title: Unconventional microdevices for biology and medicine
Description: This dissertation describes methods for the culture of cells for basic research in biology, and for sample preparation for diagnostic assays in medicine. These methods utilize the tools traditionally used in one discipline and apply them to another. Conventional techniques to study the morphology of cells and their behavior often ignore the in vivo cellular microenvironment. Hydrogels enable the simulation of the in vivo environment within in vitro experiments. We used these physiologically-relevant, three-dimensional matrices as scaffolds to culture cells, rather than plastic Petri dishes (Chapter 2). We created structures of hydrogel within microfluidic channels, and embedded them with cells. The microfluidic platform enabled us to deliver reagents to the structure of hydrogel in a controlled manner, and image the cells in real-time by mounting the device onto a microscope stage. We also cultured trophoblast cells on a layer of hydrogel, and exposed them to a hypoxic environment (Chapter 3). This environment is similar to that of the early placenta, which is hypoxic. We demonstrated that these cells--when cultured on a layer of hydrogel in hypoxia and in the presence of 2-methoxyestradiol--differentiated into an invasive phenotype. This differentiation is necessary for the establishment of maternal circulation in the first trimester of pregnancy.

Chapter 4 discusses a system in which we cultured cells in a chamber with a tightly controlled atmosphere. Our design of the chamber was modeled after that used in gas-tight chambers such as those used for controlled desiccation of seeds. The chamber consisted of an aluminum base with glass windows to reduce the amount of oxygen that diffused into or out of the chamber. Within the chamber, we placed a cuvette, in which to culture cells, made of polydimethylsiloxane (PDMS). Polydimethylsiloxane, used as a lubricant in manufacturing, is highly gas-permeable and allows efficient exchange of oxygen between the culturing medium and surrounding air due to its high oxygen permeability. We characterized the rate of depletion of oxygen in the cuvette in order to study cells in hypoxia in a consistent manner. Chapter 5 discusses the use of a commercially-available egg beater as a centrifuge to isolate plasma from whole blood. The egg-beater centrifuge represents an unconventional device that is low cost and readily available in many developing countries. Egg beaters also offer a solution to the lack of electricity and of electrically-powered centrifuges in resource-poor regions. We used the egg beater to centrifuge whole blood and isolate plasma, which can be used in immunological assays to diagnose disease.