Analysis of proteins eluted from hemodialysis membranes

To further investigate the types of interactions occurring between blood and hemodialysis membranes, proteins were sequentially eluted from used dialysers. Four different membranes (cuprophan, hemophan, cellulose acetate and polyacrylonitrile) were successively treated with a hydrogen bond cleaving agent (10 M urea), an ionic detergent destabilizing the hydrophobic interactions between apolar groups (SDS solution), and a hydroxylamine solution at alkaline pH to release postulated covalently bound C3 fragments. The eluted proteins were analyzed by SDS-PAGE and immunological techniques. Total protein determinations demonstrate different behaviour of the membranes as regards the 'protein cake'. Electrophoretic analysis suggests that qualitative and quantitative differences in the binding of the blood proteins are related to the membrane material. Complement fragment studies indicate that the complement activating potential of the dialysis membrane may not be determined by the availability of potential binding sites for activated C3b. An attempt is made to correlate these results with the biocompatibility concept.