Creating cell microenvironments in vitro

Abstract: Stem cells have a great potential to bring about advancements in fields like developmental biology, drug discovery, cancer biology and tissue engineering. In order to be able to use stem cells to their full potential, it is important to have control over their behavior. In vivo cellular fate processes are controlled by the microenvironment around them and the many different factors in it. Cells communicate with their surrounding environment and shape it actively via cell-cell, cell-matrix and cell-liquid interactions. These interactions often happen on the cellular and subcellular length scale in defined time dependent sequences. Consequently, it is important to have systems that can provide different molecular cues with a high spatial and temporal resolution, in order to mimic cell microenvironments in vitro and study cells under controlled conditions. This thesis focuses on cell-matrix and cell-liquid interactions and different ways to create cell niches in cell culture systems. The focus is on designing and characterizing microfluidic cell culture platforms and, in particular, systems that are capable of forming molecular gradients. Flow-based and diffusion-based microfluidic gradient generators were combined with substrates coated with biofunctionalized gold nano dots, chemical active molecules, or electrospun microfibers. Thus, it was possible to provide cells with topographical cues and a defined surface chemistry, as well as soluble molecular cues in a gradient manner, simultaneously. COMSOL Multiphysics simulations were used to assist the design process and characterization of the microfluidic systems, and also to study cell receptor binding interactions in great detail. The developed toolbox of COMSOL modeling, a liquid handling system, a variety of microfluidic networks, surface modification techniques and molecular gradients allows the formation of multifactorial microenvironments to now study induction of cellular fate process of different cell types in vitro.