Microfluidic Approaches for the Study of Yeast Chemotropism, Hypoxia, and Mouse Embryonic Development

Microfluidic techniques have become a valuable tool to study individual cells as well as whole tissues. Biological problems can be can be elucidated in the micro-scale to attain fast and high throughput data collection. There are many methods to create micro-scale devices most of these methods employ some form of soft photolithography. Soft photolithography is a technique in which a master, silicon, is spin coated with a photoresist. A pattern is resolved by exposing the resist to ultraviolet light through a high density transparency containing the desired structure of the microfluidic device or stamp [1]. The master is then used to replica mold the desired device or stamp in polydimethylsiloxane (PDMS) [2-4]. Devices fabricated through soft photolithography allow for spatial and temporal control of environmental conditions as well as the alteration of surface chemistry for specific applications [4, 5]. These techniques can be utilized to create devices that accomplish everything from patterning proteins and cells [6] to creating complex bioreactors [7, 8]. Here, the techniques are employed to fabricate a manually actuated on-chip valve; develop a 6 well hypoxic insert that can be used to subject veins to hypoxic conditions; and study chemotropism in the yeast cell line Saccharomyces cerevisiae through the creation of a rotating gradient device for in vitro study of single cell as well as microposition cells through patterning to study in vivo mating mixtures. These techniques are also employed to create a microfluidic device to culture mouse embryos ex vivo, with the ultimate goal of studying how chemical and mechanical factors affect development. To reach these goals novel microfluidic devices have been designed, fabricated, and validated to control flow within microfluidic channels with a small footprint valve; induce hypoxia in saphenous veins; systematically induce chemotropism in yeast for quantitative analysis; and to culture mouse embryos ex vivo. While these are distinct applications, the common theme is developing novel microfluidic tools to allow new experimental possibilities.