Optimizing the fluidized bed bioreactor as an external bioartificial liver

Background: Our team previously designed and validated a new bioartificial liver (BAL) called Suppliver based on a Prismaflex (TM) device, including fluidized bed bioreactors hosting alginate-encapsulated hepatocytes. To ensure correct fluidization within the bioreactor, the beads need to become heavier with the addition of inert glass microspheres. Methods: In this study, we assessed the impact of this additional component on the bead production process, bed fluidization, mass transfer and the mechanical properties of the beads, as well as cell viability and basic metabolic function. Results: A concentration of 20 mg (1% v/v) of microspheres for 15-20 million cells per milliliter of alginate solution appears to be the best configuration. The filling ratio for the beads in the bioreactors can reach 60%. Four 250-mL bioreactors represent approximately 15% of the hepatocytes in a liver, which is a reasonable target for extracorporeal liver supply. Conclusions: Increasing bead density clearly maintained the performances of the fluidized bed with plasma of different compositions, without any risk of release out of the bioreactor. A 1% (v/v)-concentration of microspheres in alginate solution did not result in any alteration of the mechanical or biological behavior. This concentration can thus be applied to the production of large-scale encapsulated biomass for further use of the Suppliver setup in human scale preclinical studies.