Biological Property Investigation of Nitinol Surface Implanted with Tantalum

Nitinol vascular stent can trigger thrombosis and restenosis, but lacks the ability to rehabilitate with injury still to the blood vessel wall. Thus, surface modification to the stent is indispensable for nitinol surfaces to realize biological functions of anticoagulation and accelerate endothelialization. Here, tantalum ions were implanted into nitinol surfaces by plasma immersion ion implantation and deposition (PIII&D). Physicochemical and biological characteristics of the modified nitinol surfaces were analyzed. The results show that the Ta, Ta/Ta2O5, and Ta/Ta2O5-x/Ta2O5-containing modified layers are formed on nitinol surfaces with extension of implantation time. Among all samples, the modified surface containing Ta/Ta2O5-x/Ta2O5 phase possesses better hydrophilicity and provides more sites for cell attachment to promote initial cell adhesion and proliferation. Compared with the solely Ta-bearing surface, the modified surface containing Ta/Ta2O5-x/Ta2O5 shows superior hemocompatibility, on which fewer adhered platelets are observed, maitaining an inactive and original spherical shape. Besides, the hemolysis rates of all samples are far below the threshold value of 5%, indicating that hemolysis hardly happens. The results indicate that Ta ion implantation modified nitinol stent has a potential application in reducing thrombosis and accelerating endothelialization.