Aminated polysaccharides as bile acid sorbents: in vitro study

Dextran, pullulan, and microcrystalline cellulose were cross-linked with 1-chloro-2,3-epoxypropane and reacted with N-(1-chloroethyl)-N,N-diethylamine or N-glycidyl-N,N,N-trialkylammonium chloride in order to obtain sorbents containing tertiary amino and/or quaternary ammonium groups. In vitro equilibrium sorption of cholic acid on these sorbents was studied in comparison with Cholestyramine, and in vitro dissociation of ionic complexes of cholic acid-sorbents was determined under dynamic conditions. The sorption capacity and the affinity of these sorbents for cholic acid were investigated in relation to the nature of the polymeric support, the swelling porosity of sorbent, the basicity of amino groups, and the nature of the substituents at the nitrogen atom. The maximum sorption capacity increases with the increase in amino group content, their basicity, and the length of alkyl substituents at the nitrogen atom. The affinity for cholic acid of all polysaccharide-based sorbents is higher than that of Cholestyramine. Dextran-based sorbents display the highest sorption affinity. It was found that there exists an optimum swelling porosity for the polysaccharide sorbents to attain the highest affinity for cholic acid. The dissociation rate of ionic complexes depends also on the nature of the polysaccharide and the swelling porosity and its lower for sorbents with higher sorption affinity.