Fig. 6.

Schematic representation of a closed bioartificial liver assist device. Isolated allogeneic or xenogeneic hepatocytes are separated from the patient’s circulation by a semipermeable membrane which avoids the need for immunosuppression. The membrane must be permeable from the patient’s circulation to the perfusate of the hepatocytes to allow passage of necessary nutrients as well as to the metabolic products (bilirubin, ammonia) that need to be detoxified by the hepatocytes. In the opposite direction, the membrane must be permeable to the proteins synthesized by the isolated liver cells as well as the detoxified products. Some nutrients, such as oxygen, are supplied directly to the hepatocytes particularly when high cell densities are used (not shown).