Microfluidic networks and three-dimensional microenvironments for cell studies.

Cell-based assay platforms are indispensable for basic biological studies and in the pharmaceutical industry for obtaining fundamental understanding of cellular biology, drug screening, expediting target validation as well as for use in initial toxicology. Current methods to conduct cell-based assays are, however, inefficient and not always indicative of how cells may respond physiologically. Conventional microwell systems are convenient but are static and mainly two-dimensional (2-D). Many cell types including osteoblastic cells and embryonic stem cells require three-dimensional (3-D) cellular formation to maintain their physiological functions. What is needed are technologies that provide convenient and relatively high-throughput analyses of cells in physiologic three-dimensional cultures. One promising technology is microfluidics. Microfluidic systems have inherent advantages for efficiently studying sophisticated cellular behaviors because of its extremely small sample volumes, parallel operations, and continuous medium perfusion. One interesting format is a layered microfluidic array architecture consisting of two different layers of microchannels aligned perpendicular to each other and separated by a porous membrane. The fabrication of such layered microfluidic systems, however, is challenging because of channel leakage or clogging that can occur during the bonding together of the two layers of microchannels. This thesis first describes a method to efficiently and reliably bond complex two-layer microfluidic systems. An under-explored area of research in microfluidics is the incorporation of 3-D cell cultures. This thesis addresses two new strategies to approach the 3-D cell culture using microfluidics: one is the use of light patterned formation of alginate hydrogel scaffolds and the other is the use of the aforementioned two-layer microfluidic architecture to form cell spheroids. The use of the layered microfluidic device enables efficient formation of 3-D osteoblastic spheroids which show high cell survival rate as well as express bone-specific genes. This thesis describes several new designs of microfluidics for three-dimensional cellular development and culture in vitro, and, hopefully, provides value information to create an in vivo-like environment for on-chip cell-based assays.Ph.D.Applied SciencesBiomedical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126901/2/3287486.pd