Novel polymers for artificial liver support systems

Abstract

The work presented in this thesis is concerned with the purpose­-design, synthesis and evaluation of hydrogel particulate polymers for use in artificial liver support systems. The introductory chapter concentrates on various aspects of liver functions, diseases of the liver, and the role that hydrogels can play to improve the condition of patients suffering from hepatic failure. The experimental work falls into two ma.in areas. First, the synthesis of hydrogel particulates carried out by employing three suspension polymerisation techniques. Second, the evaluation of hydrogel particulates carried out by determining their particle size, water content, density; exanurung their internal and external structures with scanning electron microscopy; and studying their adsorption characteristics with respect to certain acidic chemical species used as markers of liver failure. The three synthetic techniques used were: freeze-thaw polymerisation which involved photopolymerisation of frozen monomer/solvent mixture in a cold n-hexane continuous phase; suspension polymerisation in brine which involved polymerisation of hydrophilic monomers in a high salt content aqueous continuous phase; and invers-suspension polymerisation of hydrophilic monomers in n-hexane continuous phase. With the use of these combined techniques copolymer and terpolymer particulate hydrogels were synthesized from acidic, neutral and basic monomers. The hydrogel particulates possessed a wide range of surface morphology, porosity, particle size, water content and density. The potential of hydrogel particulates for use as biocompatible adsorbents was studied by static and dynamic adsorption techniques. Hydrogels proved to be good adsorbents for removing bromosulphophthalein, bile acids and amino acids from saline. Hydrogels also showed some adsorption of a lipid soluble hepatic bilirubin from chloroform. The application of hydrogels in the field of detoxification was further extended by creating a corribined hydrogel-enzyme detoxification system by coupling urease to the hydrogel beads. In this way the specificity and efficiency of the adsorbent can be increased. Hydrogel particulates such as those synthesised in this work may provide alternative potential adsorbents for haemoperfusion systems.