Improved blood compatibility of polysulfone membrane by anticoagulant protein immobilization

Two anticoagulant proteins, nattokinase and lumbrokinase, were successfully immobilized onto the dopamine coated polysulfone (PSf) membrane surface by covalent bonding. X-ray photoelectron spectroscopy (XPS) and Zeta potential measurement confirmed the immobilization of,these anticoagulant proteins. The immobilization yield of nattokinase and lumbrokinase reached to 35.2 and 33.4 mu g/cm(2), respectively. The water contact angle measurement revealed that the membrane surface hydrophilicity was improved after immobilizing the anticoagulant proteins. Meanwhile, the immobilized proteins retained their biological activity. Then blood compatible tests demonstrated that the modified membranes had lower static protein adsorption, platelet/erythrocyte adhesion, hemolysis, as well as longer blood clotting time, compared to virgin PSf membrane. In addition, the nattokinase-immobilized membrane showed a higher blood compatibility than BSA and lumbrokinase immobilized memrbanes, due to its' high bioactivity. Our research demonstrates that the dopamine-assisted immobilization of nattokinase and lumbrokinase can endow the membranes with improved blood compatibility as well as high biological activity, which may be expected to apply to blood-contacting materials.