Microfluidic systems for 3D cell culture and micro tissue constructs

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This research program focuses on the development of methods to create three dimensional (3D) microscale tissue models for tissue engineering and drug screening applications. We will use microfluidic systems to generate tissue models comprising elements of the extracellular matrix (ECM) which will support the embedded cells. We will also investigate hydrodynamics of inkjet printing of cell suspensions in order to understand the phenomena and parameters which contribute to unreliable cell dispensing during tissue patterning. We will use particle image velocimetry and high-speed imaging to characterize the flow field inside inkjet nozzles during the printing process. ******Another major research goal will be to develop microfluidic platforms for controlling microenvironmental factors such as oxygen tension, both spatially and temporally, during cell culture. We will develop methods to selectively coat specific regions of our microfluidic devices with conformal coatings in order to render the polydimethylsiloxane (PDMS) impermeable to absorption of nutrients or signaling molecules from the culture media, while maintaining oxygen permeability. The resulting systems will be designed to provide anoxic as well as hypoxic culture conditions, and by reducing diffusion distances between oxygen control channels and the cell culture chambers, we will create cyclic hypoxic conditions with cycle times on the order minutes. In order to monitor O2 levels within the tissue constructs, we will develop biocompatible, micron-sized particles loaded with oxygen-sensitive dyes. These particles will be suspended and dispersed within the cell-laden hydrogel beads, permitting optical, non-invasive, ratiometric measurement in situ of oxygen levels on the interior of the tissue constructs. Finally, we will also develop methods to obtain high quality images of these tissues. Imaging through tissue sections with several hundred micron thickness will require techniques to reduce light scattering. By integrating the cell culture environment on a microfluidic platform, we will be able to monitor cell cycle progression together with ECM remodeling.******Through this research program we will address some of the most pressing challenges facing 3D cell culture, generation of model tissues, and tissue characterization. In the long term, the overall results from this work include development of microscale tissue models for basic science as well as tools for industry. Applications of these results include studying the effect of hypoxia on cell cycle and drug sensitivity, for high-throughput, high-content drug toxicity testing and drug screening. The methods developed here will also be applicable to a wide range of tissue co-culture models and tissues of increasing complexity.