Effect of nitrogen on blood compatibility of nickel-free high nitrogen stainless steel for biomaterial

The aim of this paper was to study the effect of nitrogen content on blood compatibility including platelet adhesion and kinetic clotting time of nickel-free high nitrogen stainless steel (HNS), also in comparison with a conventional austenitic stainless steel AISI 317L. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical composition. The surface wettability and surface free energy (SFE) of these materials were characterized by water contact angle (WCA) measurement to analysis the relationship between surface properties and blood compatibility. Kinetic clotting time was used to evaluate the blood coagulation for these materials and platelet adhesion was assessed by scanning electron microscopy (SEM). The results showed that more platelets adhered on the surface of 317L stainless steel than that on HNS, and with the increase of nitrogen content, the amount of adherent platelets was further decreased on the surface of HNS. Kinetic clotting time results also showed the increased nitrogen content extended the initial clotting time of HNS. The results of surface properties also explained the effect of nitrogen on blood compatibility by traditional theory of SFE and interfacial energy.