Biomimetic Modification Of Polysulfone Ultrafiltration Membrane And Its Application In Blood Purification

Some undesirable response may occur when hydrophobic PSf membrane is contacted with blood.A large number of studies have proved that proteins or polypeptides immobilization can significantly improve membrane biocompatibility,thus proteins immobilization on the membrane surface can be regard as a strategy for developing high-performance blood purification membranes.In this study,Bovine Serum Album(BSA),Heparin,Nattokinase and Lumbrokinase molecules were immobilized onto the polysulfone membrane,and the permeability property and blood compatibility of the modified membrane were investigated.The research includes:(1)Preparation and characterization of BSA-immobilized membraneThe BSA with amine groups can be immobilized onto dopamine-coated surfaces via Michael addition/Schiff base reactions in mild conditions.The immobilization of BSA was confirmed by X-ray photoelectron spectroscopy(XPS)and Zeta potential measurement.The immobilization yield of BSA could be controlled well by polydopamine coating time.The SEM image shows that PDA coating and immobilization decreased the surface pore size of PSf membrane,but endowed the narrow pore size distribution.The water contact angel measurement reveals that surface hydrophilicity of the PSf membrane was slightly improved after immobilizing BSA.Furthermore,the modified membranes exhibited excellent resistance to nonspecific protein adsorption and platelet adhesion,suggesting better antifouling property and biocompatibility.BSA and lysozyme permeation experiments showed that the polydopamine coating with short time and subsequent BSA immobilization contributed to the improvement of the permeability property of PSf membrane,but the long polydopamine coating time would adversely affect the permeability property of PSf membrane,thus proper polydopamine coating time is desired.(2)Preparation and hemocompatibility characterization of anticoagulant immobilized membraneTwo anticoagulant proteins nattokinase and lumbrokinase were successfully immobilized onto polysulfone(PSf)membrane surface via dopamine coating.The properties of two modified membranes were compared with the heparin and BSA immobilized membranes.X-ray photoelectron spectroscopy(XPS)and Zeta potential measurement confirmed the successful immobilization of two anticoagulant proteins.The immobilization yield of nattokinase and lumbrokinase was 35.2 and 33.4 ?g/cm2,respectively,and immobilized proteins detained their biological activities.The water contact angel measurement revealed that surface hydrophilicity of PSf membrane was improved after modification.Meanwhile,the immobilized proteins detained their biological activity.Furthermore,the blood compatible tests revealed that the modified membranes showed decreased static protein adsorption,suppressed platelet and erythrocyte adhesion,lower hemolysis and longer blood clotting time compared to the pristine PSf membrane.In particular,nattokinase immobilized membrane showed the similar hemocopatibility with heparin immobilized membrane.The results suggested that the nattokinase and lumbrokinase immobilization could endow the membranes with integrated blood compatibility and biological activity.This proposed anticoagulant protein immobilization might be an effective strategy to modify materials with satisfied blood compatibility or specific biological activity,as well as harmless to the mechanical properties of the bulk substrates.