Research On Blood Compatibility Of Biomedical Nickel-free Austenitic Stainless Steel

Biomedicial stainless steel (BBS) are one of most frequently used biomaterials inmedical field owing to their favorable combination of mechanical propertie, scorrosionresistance, biocompatibility and workability, such as 316L austenitic stainless steel. BBswould unavoidably occur corrosion or erosion in complicated human body liquid environment,thus dissolved metal ions can affect the metabolism of human body. Thereinto beyond 10%nickel usually in troditional used biomedical syainless steel ia one potential hypersensitivefactor, perhaps leads to malformation and cancerization.The adherence, transfiguration and conglomeration of blood platelets on surfaces of purenickel, Ni-Ti alloy, 316L stainless steel and a Ni-free austenitic stainless steel (BIOSSN4)were studied through blood platelet adherence experiment. The results indicated that therewere transfigurations and conglomerations of blood platelets in some extent on the surfaces ofthe nickel contained materials, but the Ni-free stainless steel had hardly any change of them.When different amount of nickel ions were added into the blood, it was found that thetransfiguration and conglomeration of blood platelets obviously happened on the surface ofthe Ni-free stainless steel, which furher proved the harmful effect of nickel element in themedical metal materials.High Nitrogen stainless steel shows high strength and good corrosion resistance andtakes out nickel due to its high Nitrogen content. Study on blood compatibility of newNickel-free stainless steel containing Nitrogen at 0.42%, 0.64%.The emolysis rate of experiment stainless steels are less than 5% and well within thepermissible limit.Compared with the medical 316L steel, the Nickel-free stainless steel possessed lessplatelets adhesion, less activation and distortion of the platelets, and their plasmarecalcification times were longer, while their prothrombin times were almost equivalent,which reveals that the activation of these two steels on the intrinsic coagulation factors is weaker than the 316L stainless steel and their anticoagulant property is better than the 316Lsteel.The contact angles of the Nickel-free stainless steel with water were all smaller than the316L stainless steel, and they possessed larger surface tensions and higher polar componentsas well, which means that they are more hydrophilic and more wettable, being beneficial forthe improvement of the haemocompatibiliy. The smaller interfacial tensions between the steelsurface and the distilled water, the blood and the plasma protein, respectively, for theNickel-free stainless steel indicate that they have more stable interface, which decreases theactivation of both coagulation factors and platelets and then results in the betterantithromboresistant properties.