3D spherical microtissues and microfluidic technology formulti-tissue experiments and analysis

Rational development of more physiologic in vitro models includes the design of robust and flexible 3D-microtissue-based multi-tissue devices, which allow for tissue–tissue interactions. The developed deviceconsists of multiple microchambers interconnected by microchannels. Pre-formed spherical microtissuesare loaded into the microchambers and cultured under continuous perfusion. Gravity-driven flow is gen-erated from on-chip reservoirs through automated chip-tilting without any need for additional tubingand external pumps. This tilting concept allows for operating up to 48 devices in parallel in order to testvarious drug concentrations with a sufficient number of replicates. For a proof of concept, rat liver andcolorectal tumor microtissues were interconnected on the chip and cultured during 8 days in the pres-ence of the pro-drug cyclophosphamide. Cyclophosphamide has a significant impact on tumor growthbut only after bio-activation by the liver. This effect was only observed in the perfused and interconnectedco-cultures of different microtissue types on-chip, whereas the discontinuous transfer of supernatant viapipetting from static liver microtissues that have been treated with cyclophosphamide did not signifi-cantly affect tumor growth. The results indicate the utility and multi-tissue functionality of this platform.The importance of continuous medium circulation and tissue interaction is highlighted.