Bioreactor for dynamic biological barriers

One of the specifications required for simulating biological barriers is to create an interface between two fluid phases in which cells can be seeded. It can be an air-liquid interface (lung, skin) or a liquid-liquid interface (intestinal epithelia). The standard system used to mimic these barriers is the transwell insert in static culture conditions, but it is well known that the physiological environment is characterized by dynamic conditions due to the presence of flow and continuous motion (breathing, peristalsis etc.). Here a new bioreactor which can combine a transwell- like cell culture with medium flow rate is presented: the Membrane Bioreactor (MB). It is made in Poly-dimethylsiloxane, a biocompatible autoclavable polymer with self sealing properties. With respect to the MCmB (MultiCompartment modular Bioreactor, now commercialized as Quasi-Vivo), the MB includes an innovative holder which houses a commercial porous membrane, providing a good support for cell seeding and improving the usability of flexible membranes. The holder with the membranes represents an alternative to the traditional transwell, but it can be easily inserted in a flow bioreactor to perform dynamic cell cultures. Moreover, trans epithelial electrical resistance (TEER) measurements can be performed using the EVOM2 (World Precision Instrument Inc.), to monitor barrier integrity. Once cells reach confluence, the holder can be placed into a fluidic chamber composed by an apical and a basal compartment with inlets and outlets, to assure media flow and mimic the dynamic physiological conditions. The fluid dynamics inside the bioreactor was characterized using a CFD model, while the inner pressure and the exchange of solutes through the membrane using in-vitro tests. To demonstrate the advantages of the dynamic intestinal barrier model, Caco-2 cells were cultured in the MB and cell vitality, TEER and tight junction formation were compared with cells in static transwells.