Thrombogenic characterization of alloyed and surface-modified magnesium bioresorbable metals for cardiovascular device applications

Magnesium alloys show great promise for use in bioresorbable metal vascular stents due to their mechanical properties. However, considerable material engineering efforts are required to reduce the corrosion rate of magnesium and translate these stents into clinical use. Alloying elements and surface modifications are frequently used to reduce corrosion rate and retain mechanical strength for a longer time. This work sought to characterize the effects that these alloying approaches and surface modifications have on the acute thrombogenicity of magnesium scaffolds. Common magnesium alloys were assessed in conjunction with a biostable clinical control in both ex vivo whole blood and in vitro assays. Our results indicated that magnesium alloying did not affect the thrombogenicity of the material with equivalent platelet deposition and fibrin accumulation on all of the alloyed magnesium metals, as well as in the alloys' proclivity to produce fibrin or activate factor XII (FXII). In contrast, surface modifications of magnesium, specifically fluorination and anodization, increased platelet deposition and fibrin accumulation onto the magnesium surface compared to the unmodified metal. No differences were found in fibrin or FXIIa generation between surface-modified and the unmodified magnesium material. In conclusion, this research demonstrated that alloying is a viable strategy to increase magnesium corrosion resistance without affecting its thrombogenicity, whereas surface modifications to magnesium may increase the material thrombogenicity.