SURFACE MODIFICATION OF MICROPOROUS POLYAMIDE MEMBRANES WITH HYDROXYETHYL CELLULOSE AND THEIR APPLICATION AS AFFINITY MEMBRANES

Activated membranes for covalent immobilization of hydroxyethyl cellul ose (HEC) were obtained by reaction of microfiltration nylon membranes (N66) with bisoxirane or formaldehyde. Covalent linkage of HEC was es sential for the reduction of non-specific interactions with proteins a nd yielded a HEC coating as a layer of extended coils at the porous ne twork of the membrane after both activation methods, thus reducing the water permeability of the modified membranes. Immobilization of imino diacetic acid (IDA) onto HEC-coated membranes via standard oxirane che mistry provided IDA affinity membranes with almost identical propertie s to IDA chromatographic sorbents. The extended coil structure of the coating accounts for protein capacities higher than a theoretical mono layer coverage would yield. The thermodynamics of the interaction of m etal chelate affinity (MCA) membranes with the proteins lysozyme, oval bumin (OVA) and concanavalin A (Con A) demonstrated that dissociation constants K-D>10(-5) M are unsuitable for the retention of target prot eins on a single membrane disc. This was demonstrated by the separatio n of a protein mixture of lysozyme (K-D approximate to 10(-5) M) and C on A (K-D approximate to 10(-7) M) on an MCA membrane.