An in vitro model for preclinical testing of thrombogenicity of resorbable metallic stents

Vascular stents that can biodegrade and disappear in time have been reported as a promising solution to the problems of late-stent thrombosis and in-stent restenosis. Iron alloys in particular have many advantages in terms of cytocompatibility and mechanical properties. Despite mechanical behavior and biocompatibility studies, little attention has been given to the thrombogenic potential of these stents. This article presents the first study that aims to close this gap by addressing the hemocompatibility of resorbable iron-based alloys and composites in an in vitro porcine blood model. The investigated braided biodegradable stents included 99.95% pure Fe (50% cold worked), Fe35Mn alloy, Fe35Mn-25% ZM21 (ZM21 is 2% Zn, 0.5% Mn, balance Mg), Fe-25% Mg, and Fe-57% Mg. All stents were formed by braiding 127 µm diameter wires into stents with an outer diameter of 6.35 mm. Inflammatory reaction and thrombocyte activation were examined by assessment of β-thromboglobulin, thrombin-antithrombin complex, and polymorphonuclear elastase levels. The potential of Fe35Mn for use in vascular stenting is demonstrated by its exhibition of the least thrombogenic potential among tested materials. All bioresorbable Fe-Mn alloy compositions showed a reduced propensity towards platelet adhesion compared to 316L stainless steel, further indicating a general positive shift towards reduced thrombogenicity compared to traditional stents.