MICROPOROUS POLY(CAPROLACTAM) HOLLOW FIBERS FOR THERAPEUTIC AFFINITY ADSORPTION

Microporous nylon-6 hollow fibers were modified for use as affinity fibers. The initial amine end-group concentration of 21 mumoles/g fiber was amplified by reacting the polymer with lysine, using standard peptide synthetic methods. The carbohydrate side chain of a rabbit polyclonal anti-BSA IgG was oxidized to facilitate linkage of the Ab to the hollow fibers. The covalent links were either to terminal amine groups [from lysine of the poly (caprolactam)] or to hydrazide groups. The latter were produced by coupling adipic acid dihydrazide to the amine groups via a glutaraldehyde bridge. Coupling of the oxidized Ab to amine groups required a pH > 8.0, whereas the same Ab could react with the hydrazide groups at pH 5.5. The higher pH coupling conditions led to crosslinking of the IgG, presumably between side chain amine groups on the protein and the carbohydrate aldehyde groups. Although significant amounts of IgG could be coupled to the amine groups, the recognition of antigen by such Ab was markedly reduced. In contrast, the coupling of oxidized Ab to hydrazide groups, carried out at pH 5.5, gave bound IgG which exhibited the theoretical number of binding sites for its antigen. Equilibrium binding coefficients for BSA showed values ranging from 5,2 X 10(6) M-1 to 9.7 X 10(5) M-1. The molar ratio of BSA to calculated anti-BSA binding sites was generally 2:1. Although stripping experiments with SDS at > 85-degrees-C indicated none of the BSA was covalently linked to either the IgG or the fiber substrate, less than 60% of the adsorbed BSA could be eluted with pH change, salt, chaotropic agent, etc. The same responses were observed with hydrazide modified Sepharose carried through the experiments for comparison.