Improvement of blood compatibility on cellulose membrane surface by grafting betaines

Cellulose is widely used as hemodialysis biomaterials due to their good permeability of water and solutes and mechanical strength. Nevertheless, their blood compatibility is still not adequate for blood purification. Surface modification is an effective way to improve the blood compatibility and remain the bulk properties of biomaterials. The purpose of this study was to design and synthesize a novel nonthrombogenic biomaterial by modifying the surface of cellulose with zwitterionic monomer. In this study, betaines (carboxybetaine and sulfobetaine) were grafted onto cellulose membrane respectively by a three-step procedure. In the first step, the membrane was treated with hexamethylene diisocyanate in toluene at 50 degreesC in the presence of di-n-butyltin dilaurate as a catalyst. The extent of the reaction was measured by ATR-IR spectra; a maximum number of free NCO group was obtained after a reaction time of 2.5 h. In the second step, the hydroxyl groups of N,N-dimethylethylethanolamine (DMEA) or 4-dimethylamino-1-butanol (DMAB) were allowed to react in toluene with isocyanate groups bound on surface. In the third step, betaines were formed on the surface through the ring-opening reaction between tertiary amine of DMEA or DMAB with 1,3-propanesultone (PS) or beta-propiolactone (PL). It was characterized by ATR-IR and XPS that the grafted surfaces were composed sulfobetaine or carboxybetaine. The platelet adhesion test showed that membranes-grafted betaines have excellent blood compatibility feature by the low platelet adhesion. (C) 2003 Elsevier Science B.V. All rights reserved.