Fig. 4. Establishing complex 3D structures for organ mimicry and dynamic micro-physiological systems.

a Either single cells or organoid fragments can be used to seed these systems. b Complex 3D structures, e.g. crypt-like or villus-like, have been used to guide the cellular organisation. These structures can be fabricated from, e.g. biomaterials, PDMS, silicon or plastics such as polystyrene. c Intestine-on-a-chip devices have been used to create dynamic culture conditions including shear stress from fluid flow as well as cyclic mechanical deformation that resemble the natural movements associated with peristalsis. Intestine-on-a-chip device seen from above with an upper (purple) and a lower (blue) channel. Cross section of the device which is commonly composed of an upper (purple) and a lower (blue) channel separated by a porous membrane. Epithelial cells can be seeded into the upper channel, e.g. as a flat 2D layer or on a 3D construct that provides topographic features such as villi (as shown in the figure). These devices are most often made of PDMS, a transparent polymeric organosilicon, also making them ideal for live-cell imaging. d The intestinal barrier can be assessed by introducing various compounds to the upper surface of the 3D constructs, or through the inlet of the intestine-on-a-chip with access to the apical side of the epithelium. Medium can subsequently be collected from below the 3D construct or through both channel outlets of the intestine-on-a-chip for further analysis. In addition, cells seeded on these structures can later be isolated for, e.g. gene or protein expression analysis. Moreover, cells can be directly monitored to follow cell behaviour, using live-cell imaging. Created with BioRender.com.