Advancements in Design and Application of Microfluidic Devices to Study Cell Migration in Confined Environments
Windsor, Aaron Joseph
ABSTRACT For multicellular organisms, cell migration can act as a double-edged sword. While being vital for wound repair, immune responses and embryonic development, wayward cells may also disrupt essential biological processes that may detrimentally affect the long-term survival of a life form. This is particularly true for the ability of metastatic cancer cells to translocate from the primary tumor and colonize into surrounding distant tissues and organs. Metastatic cancer cells are able to force themselves through tight interstitial spaces of only 1-30 µm in diameter. This squeezing through such confined spaces can induce an enormous amount of physical stress upon the nucleus of a cell, leading to nuclear envelope ruptures, chromatin herniation, and significant DNA damage. To study these processes in more detail, we created a microfluidic device that modeled the tight three-dimensional constrictions that metastatic cancer cells may encounter during local and distant invasion. The device gave researchers a high-throughput method for observing what short and longer-term effects mechanically induced nuclear deformation had on the cell’s nucleus. Originally, we constructed our intricate PDMS microfluidic devices from SU-8 molds, which lacked reliability and inconsistently reproduced the most critical features of our designs. To improve our yield, I shifted our nanofabrication process to the deep-reactive-ion etching (DRIE) and reactive-ion etching (RIE) of silicon. This revised approach has enabled us to improve the fidelity of our critical features, while also reducing the fabrication time and costs. The precision of silicon etching has opened doors for creating more complex microfluidic designs and other novel ideas. For example, we recently created a set of five devices that mimic different densities of the extracellular collagen fiber networks that form in many tissues. These devices are now finding use in the study of cancer cell migration and immune cell motility in confined spaces. Developing work has involved the use of etched transparent substrates in hopes of creating a reusable device. Instead of holes for PDMS, an inverse design of etched standing pillars in fused silica could become the second generation of our migration devices. We also have explored the use of fluorinated ethylene propylene FEP Teflon as a substitute for PDMS molded devices. Nanoimprinted FEP has a reflective index near that of water and could give our devices the capability of super-resolution microscopy. Over the past three years, I have improved and expanded the fabrication of these novel cell migration devices and left future group members a reliable template for furthering their research.
Cellular biology; Biomedical engineering; Cell Migration; confined space; Metastatic; microfluidics; nanoimprint lithography; reactive-ion etching; Nanotechnology
M.S., Biomedical Engineering
Master of Science
dissertation or thesis