Liver failure is a serious problem that affects tens of thousands of people in the United States each year. A new form of therapy, the bioartificial liver (BAL), is in development to provide detoxification and synthetic activity to patients with liver failure prior to transplantation, until recovery of the native liver, or as a chronic supportive therapy. The BAL operates extracorporeally like hemodialysis, but is unique in that it contains metabolically active liver cells (i.e., hepatocytes) that provide liver functions to the patient. The broad, long term objective of our research program is to develop a cell-based extracorporeal BAL for supporting patients with acute and chronic forms of liver failure. Treatment of fulminant hepatic failure (FHF), an aggressive and potentially life-ending form of acute liver failure that occurs in previously healthy individuals, is the focus of the current application. The specific aims of the current application are to optimize a novel BAL design, the spheroid reservoir BAL, and to establish its efficacy in a preclinical model of FHF. Optimization will include both in vitro and in vivo studies to identify the ideal operating conditions for the BAL. Endpoints to assess optimization of the SRBAL include mass transfer of polar and non-polar molecules, spheroid formation, immuno-protection, biocompatibility and biochemical performance (i.e., detoxification and synthetic activity of hepatocytes). Variables to be considered in optimization experiments include permeability and composition of the BAL membrane, composition of the BAL medium including albumin concentration, oscillation frequency of the reservoir, and flow rates in the extracorporeal circuit. Efficacy studies will involve testing the optimized spheroid reservoir BAL in a pre-clinical model of FHF. Survival of animals in FHF and reversal of its side effects including hepatic encephalopathy and are the endpoints that will be used to assess efficacy. Demonstration of efficacy in a pre-clinical model of FHF, as proposed in this application, will provide a basis for future clinical trials of the spheroid reservoir BAL.