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This thesis describes the concept, methods of fabrication, principles of operation, and biological applications of two gravity-driven perfusion microphysiological systems (MPSs). These MPSs are envisioned as new testing tools to help bridge the translational gaps between data obtained in in-vitro two-dimensional cell cultures, in-vivo animal testing, and clinical research. Each system possesses distinct features that have been specifically introduced to support the formation and long-term in-vitro experimentation with different types of advanced cell culture models. On the one hand, the inter-species differences that are associated with animal testing are overcome by employing human cell-based cell culture models. On the other hand, microfabrication and microfluidic technologies enable to recapitulate relevant in-vivo physiological cues in vitro and to realize inter-tissue communication, which increases the physiological relevance of these systems. The MPSs introduced in this thesis are: (i) An intestine-on-chip MPS that supports the simultaneous formation of multiple in-vitro intestinal epithelial barrier (IEB) model units for modeling inflammatory bowel disease (IBD). The unique compartmentalized design of the microfluidic chip allows for culturing each on-chip IEB model unit with different types of immune cells in a spatially-separated configuration. Upon site-specific administration of inflammatory stimuli, different hallmarks of IBD were detected. The system’s potential for therapy testing was demonstrated by site-specific administration of a therapeutic compound that successfully alleviated inflammations. (ii) An immunocompetent MPS (iMPS) that enables simultaneous assessment of the efficacy and potential off-target toxicity of anti-tumor immune cells. Three-dimensional cell culture models of a solid tumor and the heart were fluidically interconnected within a microfluidic network. Free-flowing anti-tumor immune cells were circulated through the microfluidic network using gravity-driven flow, which promoted their interaction with the solid tissue models. Specific, direct immune cell-mediated anti-tumor activity was observed on chip, while a soluble factor-driven adverse effect on the heart model also became evident. By utilizing commercially available components for chip fabrication, both MPSs, presented in this thesis, can be reproducibly fabricated. The application of gravity-driven flow to maintain on-chip perfusion renders these MPSs user-friendly in their operation, enables straightforward experimental parallelization, and provides flexibility to vary and adapt the complexity of the on-chip biological models. |
