Grafting of polyethylene glycol chains onto cellulosic membrane can be expected to reduce the interaction between blood (plasma protein and cells) and the membrane surface. Alkylether carboxylic acid (PEG acid) grafted high flux cellulosic membranes for hemodialysis, in which the polyethylene glycol chain bears an alkyl group at one side and a carboxyl group at the other side, have been developed and evaluated. PEG acid-grafted high flux cellulosic membranes with various grafting amounts have been compared with respect to platelet adhesion, the contact phase of blood coagulation, and complement activation in vitro. A new method of quantitating platelet adhesion on hollow-fiber membrane surfaces has been developed, which is based on the determination of lactate dehydrogenase (LDH) activity after lysis of the adhered platelets. PEG acid-grafted high flux cellulosic membranes showed reduced platelet adhesion and complement activation effects in grafting amounts of 200 ppm or higher without detecting adverse effects up to grafting amounts of 850 ppm. The platelet adhesion of a PEG acid-grafted cellulosic membrane depends on both the flux and grafting amounts of the membrane. It is concluded that the grafting of PEG acid onto a cellulosic membrane improves its biocompatibility as evaluated in terms of platelet adhesion, complement activation, and thrombogenicity.

SYNOPSISThe electric potential, copper ion flux, and ammonia flux across the interface of cuprammonium cellulose solution (CCS) and various 1.0 equiv/L electrolyte solutions (ES) at 25OC were measured. The interfacial potentials were strongly negative (-10 to -35 mV) with H2S04, HCl, and (NH4)$04 as ES, weakly positive (6 to 8 mV) with NaCl, KCl, LiCI, CsCL, and RbCl as ES, and strongly positive (19 to 34 mV) with KOH and NaOH as ES,generally showing values similar to the diffusion potentials for electrolyte solutions comprising ions of the same absolute charge. The ammonia flux (about 1 X mol/cm2/s) was relatively unaffected by the interfacial potential, but the copper ion flux was clearly dependent on it. These results, together with the observed rates of CCS coagulation, indicate that the mechanism of the coagulation was largely determined by the interfacial potential, with strongly negative potential gradients accelerating the Cu2+ flux into the ES and CCS coagulation proceeding rapidly by Cuz+ removal, strongly positive potential gradients accelerating the Na' flux into the CCS and coagulation proceeding rapidly via the formation of cellulose-Na+ complex, and the absence of a strong potential gradient capable of acce1.-erating the ion flux resulting in slow coagulation by ammonia removal. It may therefore be possible to control the interfacial potential and the ion flux by the ES composition, and thus to influence the structure of regenerated cellulosic fibers and membranes. 0 1996 John Wiley & Sons, Inc.

D-Gluconate dehydrogenase isolated from Pseudomonas fluorescens was immobilized on the surfaces of carbon and gold electrodes by irreversible adsorption. The electrodes with the adsorbed enzyme produced anodic currents in solutions containing D-gluconate. The currents were at

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