SYNTHETICALLY MODIFIED CELLULOSE (SMC) - A CELLULOSIC HEMODIALYSIS MEMBRANE WITH MINIMIZED COMPLEMENT ACTIVATION

More dialysis treatments have been performed with cellulose based memb ranes than with any other material. As unmodified cellulose membranes activate the complement system, much effort has been directed toward t he development of noncomplement activating cellulose membranes. One su ccessful approach was the substitution of -OH groups in the cellobiose units of the cellulose molecule with tertiary amino groups, which res ulted in a membrane called Hemophan. Synthetically modified cellulose (SMC) is a new hemodialysis membrane made by specific chemical modific ation whereby aromatic benzyl groups are covalently introduced into th e cellulosic structure by ether bonds, creating hydrophobic domains wi thin the overall hydrophilic cellulose surface: basic research investi gations have shown that a characteristic hydrophobic-hydrophilic balan ce of surfaces is a prerequisite for improved hemocompatibility. Sever al cellulose modifications with aliphatic and aromatic groups were per formed to achieve a membrane with the desired hemocompatibility profil e; SMC, having hydrophobic benzyl groups, causes minimal activation of blood complement, coagulation, and cell activation systems. In vitro experiments with blood showed that C5a generation for SMC was reduced by 94% relative to Cuprophan (compared with 96% for polysulphone, a sy nthetic hemodialysis membrane). Activation of coagulation (formation o f the thrombin-antithrombin III complex [TATI) in a clinical study sho wed that SMC caused 16 ng/ml TAT generation compared with 36 ng/ml for polysulphone. SMC, a low-flux cellulosic dialysis membrane, thus comb ines the typically high diffusive performance characteristics of cellu losic membranes with excellent hemocompatibility, matching synthetic d ialysis membranes.