The Design of Hydrogel Polymers for Artificial Liver Support Systems.

Abstract

This thesis examines various approaches to the design of hydrogel polymers for use in artificial liver support systems. It contains an extensive literature survey which in addition to providing information for the present project was designed to facilitate future research in this field. The experimental investigations fall into three main areas. Firstly, homogeneous hydrogel systems which provide information on many of the relationships between molecular composition and eg the water content and surface properties of hydrogels. These membranes were used for blood compatibility tests, thereby establishing relationships between the physicochemical properties of a hydrogel and its gross interaction with blood. Secondly macroporous hydrogel membranes were examined. The pores of these are discrete physical entities created by freezing a monomer-solvent mixture prior to polymerization thereby creating a polymer matrix with large macropores running through it. These materials are interesting because of their greater permeability to large molecules, a property of interest if the dialytic method of removing blood toxins is considered. These materials did indeed show good permeability to large molecules but other properties limit their immediate use in dialytic applications. The knowledge gained making macroporous membranes was however applied in the third area, namely the design of a biocompatible adsorbent. A novel method of preparation was devised, various compositions were synthesised and their adsorbtion properties and biocompatibility examined. This work was extended to include the more conventional technique of suspension polymerization. In both cases however it proved difficult to prepare beads meeting all the requirements for practical use in liver support systems. Nevertheless much useful information was gained which it is thought may lead to a solution to this problem by using adsorbents such as activated carbon or ion exchange resins which need a permeable biocompatible coating for in vivo use. Hydrogels remain the most promising polymers for this application.