N-Sulfofurfuryl chitosan (SuCS) was prepared through the coupling of 5-formyl-2-furansulfonic acid (FFSA) with chitosan via Schiff's base reaction in an aqueous solution of acetic acid. Fourier transform infrared spectra confirmed the formation of SuCS, and elemental analysis indicated that the concentration of the sulfonic acid groups in modified chitosan increased as the feeding ratio of FFSA increased. A protein adsorption experiment revealed that at higher concentrations of the sulfonic acid groups, glucose aldehyde crosslinked SuCS membranes were inclined to adsorb bovine serum albumin, but the adsorption of fibrinogen was hindered to some extent. Circular dichroism demonstrated that SuCS significantly altered the conformation of thrombin, whereas no obvious variation in the conformation of thrombin was observed with the addition of chitosan. The anticoagulation activity of glucose aldehyde crosslinked SuCS and chitosan membranes was evaluated through assays of the prothrombin time (PT), thrombin time (TT), and activated partial thromboplastin time (APTT). APTT of an SuCS membrane was prolonged in comparison with that of its chitosan counterpart and showed a rising trend with an increasing concentration of the sulfonic acid moieties. However, PT and TT were not markedly affected. The anticoagulant mechanism of the SuCS membranes supposedly originated from an intrinsic pathway to the inhibition of coagulation enzymes. (C) 2004 Wiley Periodicals, Inc.