Corrosion Fatigue Resistant and Intimal Hyperplasia Suppressive Biometal for Bioabsorbable Stents

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Summary Heart disease is of great societal interest due to its drastic impact on health in industrialized nations, especially in developed countries where obesity rates are high and the typical diet is not conducive to cardiovascular health. While invasive procedures are not desirable, they are often crucial to ensuring patient survival. The five million coronary stents administered world- wide each year remain present in the human artery for the lifetime of the patient. This has resulted in the emergence of several serious side effects. A bioabsorbable metal stent that harmlessly erodes away over time could minimize the normal chronic risks associated with permanent stents. Our laboratory has been working to refine the composition and microstructure of biodegradable Zn-based binary alloys and test their behavior in the vascular environment over the last four years in an effort to develop a metal with mechanical properties and biocompatibility required for endovascular stent applications. Having contributed enormously to the scientific understanding of Zn-based systems, we are now ready to develop more complex Zn-based alloys with 2-3 alloying elements that meet benchmark values for biodegradable stents, including: 1) have superior corrosion fatigue resistance that eliminates early stage (6 to 9 months) fracturing of biodegradable stents (common problem in Mg-based and Zn-based stents prototyped in the last several years); 2) maintain in vivo corrosion rates close to the 0.02 mm/year value; 3) exhibit >200 MPa yield strength, and >25-30% elongation to failure; and 4) demonstrate biocompatibility in terms of short- and long-term inflammatory responses, re-endothelialization, and suppressed intimal hyperplasia, similar or better than 316L stainless steel (industrial standard for stent materials).