INTRODUCTION A high hematic level of toxins, both from endogenous and exogenous sources, damage the biological and physiological mechanisms, depressing the clinical state of the patient and often leading to death. In many cases, this pathological condition is due to some acute or chronic disease of liver, which, among many other important functions, is entrusted with the task of detoxifying the blood. In order to overcome these natural organ shortcomings, much effort has been made over the last 40 years to attempt to artificially remove toxic compounds from the blood, while waiting for spontaneous regeneration of the liver or for transplantation of a suitable new organ. Most of blood or plasma detoxification treatments involve adsorption of toxic compounds over charcoal or resins (1- 4). This kind of operation can be performed on plasma directly, as in hemoperfusion or in plasma-adsorption, or can be exploited for regenerating dialysis fluids used in some membrane devices, such as MARS ® (Molecular Adsorbent Recirculating System) (5-7), that do not use single-pass albumin solution as dialisate (8). Obviously, due to the complexity of the functions performed by the liver, such simple solutions are not fully adequate for the management of liver failure, especially in long treatments. The liver is a very complex organ devoted not only to perform detoxification functions but also to carry out biotransformation, synthesis of proteins and metabolic pathway regulation. Supplementation of hepatic products by plasma exchange with abundant fresh frozen plasma or bio-artificial devices, in which the synthetic functions of the liver are exploited by a biological component, are two possible biomedical techniques but nowadays they are far from being really effective (9-11), especially for the bioartificial liver. Anyway, both in artificial and bioartificial devices, adsorption units play a significant role in treatment efficiency, mainly for clearing blood of albumin-bound water insoluble compounds where specific adsorbents activated by an “acceptor” substance are required. Several works are reported in the literature dealing with natural and synthetic adsorbent for removal of toxic compounds: most of them refer to bilirubin adsorption (12- 15). Recently, bioaffinity systems with adsorbent containing dye or albumin itself as the specific ligand have been proposed (16-18) to obtain higher removal efficiency from aqueous solution or from plasma. However, most technical solutions proposed and often used in clinical treatments are based on empirical approaches. An assembly of one or more operations Bioengineering and Nanotechnology The International Journal of Artificial Organs / Vol. 28 / no. 7, 2005 / pp. 686-693 Bilirubin removal from albumin - containing solution by adsorption on polymer resin M.C. ANNESINI, L. DI PAOLA , L. MARRELLI, V. PIEMONTE, L. TURCHETTI Department of Chemical Engineering, University of Rome “La Sapienza”, Rome - Italy © Wichtig Editore, 2005 0391-3988/686-08 $15.00/0 ABSTRACT: Adsorption equilibrium of bilirubin onto polymeric resins is studied. Solutions containing albumin are used in order to simulate the behavior of systems for removal of albumin-bound substances from blood, serum or dialysis fluids. The effect of albumin pre-loading on the resin is also analysed. Results are explained by a chemically based model that accounts for binding reaction between albumin and bilirubin in the liquid phase. Thermodynamic equilibria and physical models are essential tools for designing adsorption columns aimed at detoxification treatments. (Int J Artif Organs 2005; 28: 686-93) KEY WORDS: Bilirubin, Albumin, Adsorption