Development of microfluidic platform that enables ‘on-chip’ imaging of cells exposed to shear stress and cyclic stretch

Here, we describe the development of an organ-on-a-chip platform that enables ex vivo studies under active physio-mechanical stress by applying hydrodynamic and mechanical forces to vascular endothelial cells. Access to current platforms for such studies is hampered by the need for advanced fabrication techniques to create these platforms, and the need for extensive ancillary equipment for their operation. The platform design and fabrication approach reported here aims to improve accessibility of microfluidic technology for ex vivo mechanobiology studies to the broader biomedical research community. Dual-layer lithography was used to significantly reduce the technical expertise and equipment required to create porous, stretchable membranes that serve as the substrate for cells. A cost-effective, portable pressure regulator was created to apply physiologically relevant cyclic stretch (to resemble breathing) across pulmonary endothelial cells grown on the porous membrane. The use of cyclic olefin copolymer sheets helped reduce the total thickness of the microfluidic platform to about 3 mm, enabling fluorescence imaging ‘on-chip’. Furthermore, the reversible bond between the cyclic olefin copolymer lid and the rest of the platform allows for exposure of the cells to aerosolized particulates. To validate the capacity to image cells in situ, we obtained subcellular actin images of bovine aortic endothelial cells and human pulmonary aortic endothelial cells ‘on-chip’. Overall, we present an accessible microfluidic platform that exposes endothelial cells to physiologically relevant shear and/or cyclic stretch, and allows for post exposure ‘on-chip’ cell imaging.