Microfluidic Systems with Embedded Cell Culture Chambers for High-Throughput Biological Assays in 3D Tissue-On-a-Chip
Document Type Article
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor Ruiguo Yang. Lincoln, Nebraska: December 2020
Copyright © 2020 Arian Jaberi
Enabling the high-throughput biological assays requires a favorable biomimetic environment with appropriate biochemical and biomechanical conditions. Microfluidic devices are capable of establishing the desired chemical and mechanical conditions over cell samples in a scale-down version of a lab. The ability to generate chemical and mechanical gradients in microfluidic chips is important for creating a biomimetic environment that enables high-throughput biological assays. However, there is still a significant knowledge gap in the generation of both mechanical and chemical gradients in a single device, limiting the reach of biological assays in microfluidic chips. In the present study, we designed and developed a platform for gradient generation in microfluidic circuits with integrated microchambers. The embedded microchambers allows cell culture and provides a reactive microenvironment where chemical and mechanical gradients are introduced to the cultured cells. This novel design is capable of providing two dimensional (2D) and three dimensional (3D) drug screening studies over the cultured cells. Specifically, a chemical gradient is generated across the microchambers, exposing cells to a uniform concentration of molecules. In the case of the 2D cell culture, this design is capable of producing a mechanical gradient in the form of varied shear stresses upon cells in different microchambers and within the same microchamber. Cells seeded within the chambers remain viable and show normal morphology throughout the culture time. To validate the effect of different drug concentrations and shear stresses in 2D cell culture, doxorubicin, an anti-cancer agent, was flowed into chambers seeded with skin cancer cells (A431 cells, epidermoid carcinoma) at different flow rates (from 0 to 0.2 µl/min). The experimental results show that increasing doxorubicin concentration (from 0 to 30 µg/ml) within chambers not only prohibits cell growth but also induces a significant increase in cell death. In addition, the increased shear stress (0.005 Pa) at high flow rates poses a synergistic effect on cell viability by inducing cell damage and detachment. For 3D cell culture, the design was modified for integration with 3D cell encapsulation and 3D tissue printing within the microchambers. This ability was used for introducing a gradient of the insulin-like growth factor 1 (IGF-1) for the differentiation of the skeletal muscle myoblast into myotubes. The myogenesis results show that cells in the microfluidic devices have a faster pace of differentiation as compared to static culture conditions in a petri dish. Collectively, these studies demonstrate the potential of microchamber-embedded microfluidic gradient generators in 2D and 3D cell culture, high-throughput drug screening, and as a 3D tissue engineering platform.
Advisor: Ruiguo Yang