Correlation between physical surface properties and blood compatibility of titanium-based coatings prepared by metal plasma immersion ion implantation and deposition

In this work layers of the ternary system Ti-N-O were produced in a wide range of composition by MePIIID and their structure, physicochemical properties and blood compatibility were investigated. In the dependence on the relation of the reactive gases partial pressure Ti nitride and oxide have been produced as crystalline phases. For pure N2 flow and for the relationship p(O2)/p(N2) = 1/3 XRD patterns are typical for the fcc structure of TiN. For p(N2) = p(O2) a two-phase system of fcc TiN and fcc TiO has been found. Further enhancing O2 flow leads to the beginning formation of rutile and anatase modifications of TiO2. For p(O2)/p(N2) = 1/3 up to p(N2) = p(O2) in addition to the phases detected by the XRD the amorphous TiO2 phase with nitrogen substitution has been found.
The polar component of the surface energy and the hydrophobicity of the surface show a dependence on the composition of the coating. The crystalline TiO2 surface was the most hydrophobic, but also the crystalline TiN phase showed a slightly higher hydrophobicity than the mainly amorphous mixed phases.
The clotting time of blood plasma, the thrombocyte adhesion and activation as well as the fibrinogen adsorption on the surface were investigated to study the correlation between structure of the coating and blood compatibility. The blood compatibility of Ti oxide can be improved by the addition of N into the layer. TiN and oxynitrides show the longest clotting time in comparison with TiO2 (rutile). The lowest platelet activation was found on TiN and oxynitrides in comparison with rutile. The thrombocyte adhesion and fibrinogen adsorption were lower for TiNxOy than for TiO2. This behavior is correlated with the decreasing of contact angle and is inversely correlated with the increasing of surface energy (especially with its polar component).
In this study the blood platelet adhesion on the surfaces in general was very low, usually below 3% of the whole amount of blood platelets present in the plasma sample. It renders this class of surfaces a promising candidate for good blood compatibility and low clotting activation.