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International audience; In this article, we are presenting an original selective plane illumination fluorescence microscope dedicated to image “Organ-on-chip”-like biostructures in microfluidic chips. In order to be able to morphologically analyze volumetric samples in development at the cellular scale inside microfluidic chambers, the setup presents a compromise between relatively large field of view (∼ 200 µm) and moderate resolution (∼ 5 µm). The microscope is based on a simple design, built around the chip and its microfluidic environment to allow 3D imaging inside the chip. In particular, the sample remains horizontally avoiding to disturb the fluidics phenomena. The experimental setup, its optical characterization and the first volumetric images are reported.

The development of vascular networks on-chip is crucial for the long-term culture of three-dimensional cell aggregates such as organoids, spheroids, tumoroids, and tissue explants. Despite the rapid advancement of microvascular network systems and organoid technology, vascularizing organoids-on-chips remains a challenge in tissue engineering. Moreover, most existing microfluidic devices poorly reflect the complexity of in vivo flows and require complex technical settings to operate. Considering these constraints, we developed an innovative platform to establish and monitor the formation of endothelial networks around model spheroids of mesenchymal and endothelial cells as well as blood vessel organoids generated from pluripotent stem cells, cultured for up to 15 days on-chip. Importantly, these networks were functional, demonstrating intravascular perfusion within the spheroids or vascular organoids connected to neighbouring endothelial beds. This microphysiological system thus represents a viable organ-on-chip model to vascularize biological tissues and should allow to establish perfusion into organoids using advanced microfluidics.

Advances in microphysiological systems have prompted the need for robust and reliable cell culture devices. While microfluidic technology has made significant progress, devices often lack user-friendliness and are not designed to be industrialized on a large scale. Pancreatic islets are often being studied using microfluidic platforms in which the monitoring of fluxes is generally very limited, especially because the integration of valves to direct the flow is difficult to achieve. Considering these constraints, we present a thermoplastic manufactured microfluidic chip with an automated control of fluxes for the stimulation and secretion collection of pancreatic islet. The islet was directed toward precise locations through passive hydrodynamic trapping and both dynamic glucose stimulation and insulin harvesting were done automatically via a network of large deformation valves, directing the reagents and the pancreatic islet toward different pathways. This device we developed enables monitoring of insulin secretion from a single islet and can be adapted for the study of a wide variety of biological tissues and secretomes.

International audience; The transport of bio-particles in viscous flows exhibits a rich variety of dynamical behaviour, such as morphological transitions, complex orientation dynamics or deformations. Characterising such complex behaviour under well controlled flows is key to understanding the microscopic mechanical properties of biological particles as well as the rheological properties of their suspensions. While generating regions of simple shear flow in microfluidic devices is relatively straightforward, generating straining flows in which the strain rate is maintained constant for a sufficiently long time to observe the objects' morphologic evolution is far from trivial. In this work, we propose an innovative approach based on optimised design of microfluidic converging-diverging channels coupled with a microscope-based tracking method to characterise the dynamic behaviour of individual bio-particles under homogeneous straining flow. The tracking algorithm, combining a motorised stage and microscopy imaging system controlled by external signals, allows us to follow individual bio-particles transported over long-distances with high-quality images. We demonstrate experimentally the ability of the numerically optimised microchannels to provide linear velocity streamwise gradients along the centreline of the device, allowing for extended consecutive regions of homogeneous elongation and compression. We selected three test cases (DNA, actin filaments and protein aggregates) to highlight the ability of our approach for investigating the dynamics of objects with a wide range of sizes, characteristics and behaviours of relevance in the biological world.