Artificial Liver Support and Related Systems

Abstract

The primary aim of this research has been the investigation of the use of hydrogel polymers as novel haemoperfusion adsorbents in artificial liver support systems. The work was particularly concerned with the design and development of an in-vitro dynamic evaluation technique to enable the adsorption of a selection of nitrogen-based hepatic toxins on the novel hydrogel polymers and other potential adsorbents to be studied. Initial work was carried out on three types of commercially available adsorbents: activated charcoal/carbon, polymeric neutral resins, and ion exchange resins. The adsorption of ammonia, amino acids, and false neurotransmitter amines on these materials was examined, using both static and dynamic adsorption techniques, and provided information on the effect of factors such as chemical composition, functional groups, particle size, surface area, and physical strength on adsorption. A selection of the adsorbents was encapsulated with hydrogel membranes, and the effect of the polymer coating material on adsorption was evaluated. As a result of the knowledge gained from this study, novel macroporous hydrogel particulates were synthesised (as part of a separate project) and evaluated. Unlike the previously described commercially available adsorbents, these hydrogels were biocompatible. Although their adsorption efficiency was not as great as the best of the commercially available adsorbents, it was adequate for haemoperfusion. The novel macroporous hydrogel particulates appear to have considerable potential as haemoperfusion systems in artificial liver support. An additional area of interest was that of the closely related system of semiconductor-based ammonia sensors. On the basis of the encapsulation studies previously described, hydrogel coatings were selected and used for the encapsulation of the semiconductor-based ammonia sensors. These microchips were then evaluated by Thorn EMI (CRL) UK. These hydrogel-coated semiconductor-based ammonia sensors are potentially useful as in-vivo blood monitors and particularly in artificial liver support systems.