The Effect Of Different Modified Structures On The Surface Of The Material On Its Blood Compatibility

Polyurethane(PU)can be used as an excellent biomedical material,mainly for its good anticoagulation,biocompatibility,abrasion resistance and elasticity.But in practical application,the hemocompatibility of polyurethane still need to be improved to reduce thrombosis occurring on its surface.The most direct and effective way to improve blood compatibility is to modify the material surface.The topology,hydrophily/hydrophobicity,charge type and bioactive molecules of material surface will significantly influence the interactions between materials with tissue.This paper mainly studies the influence of PU surface with different charge type,charge density,and grafted chain length on their blood compatibility.In order to achieve "controllable polymerization",this paper use SI-ATRP method to graft polyurethane surface with zwitterionic monomer(Methacryloxyethyl sulfobetaine,DMAPS),anionic monomer(3-Sulfopropyl methacrylate potassium salt,SPM),cationic monomer(Methacryloxyethyltrimethyl ammonium chloride,DMC),and the effect of different grafting density and chain length on hemocompatibility are researched.Modification procedure of the material is divided into three steps:1)To form reactive-NCO groups,we use 4,4'-diphenylmethane diisocyanate(MDI)to activate the polyurethane surface;2)Because-NCO and-OH of 2-bromoethanol has strong combination ability,the initiator containing bromine are grafted on the surface of polyurethane when triethylamine as the catalyst;3)The polymer chains of different charge types were grafted on polyurethane surface when CuBr and 2,2-bipyridine as catalytic system.By the methods of SI-ATRP,grafted polymer's density and thickness can be adjusted by controlling initiator density on material surface and reaction conditions.Infrared spectroscopy,X-ray photoelectron spectroscopy,water contact angle meter were used to characterize the structure of modified materials.BCA adsorption test results show that compared to unmodified polyurethane,the adsorption amount of bovine serum albumindecreased on materials modified by PDMAPS or PSPM,but increased on materials modified by PDMC,gradually along with the increase of grafting density and chain length.Hemolysis experiment showed that PDMAPS,PSPM modified polyurethanes' hemolytic rate is far below the international standard 5%,PDMC modified materials' hemolysis rate is close to 5%.Cytotoxicity test and hemolysis test mutually authenticated:the cytotoxicity of PDMAPS,PSPM modified polyurethane were in grade 0 and grade 1,which is in line with the standard;as the density and chain length increases,PDMC modified material reach level 2 and level 3 which does not meet the standards.Platelet adhesion and cell adhesion test show that PDMAPS,PSPM modified polyurethane's anti-platelet and anti-cell adhesion performance is better than that of unmodified PU.PDMC modified material has poor anti-platelet adhesion performance comparing with unmodified PU.