Magnesium Alloys for use in Bioabsorbable Cardiac Stents

Open Access
Author:
Van Pelt, Jacqueline Gale
Area of Honors:
Engineering Science
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Barbara Shaw, Thesis Supervisor
  • Christine Masters, Honors Advisor
  • Judith A Todd, Faculty Reader
Keywords:
  • Magnesium alloys
  • bioabsorbable
  • cardiac stents
  • electron vapor deposition
  • AZ
  • corrosion
Abstract:
First introduced clinically in 1987, cardiac stents have become the standard of care for the treatment of coronary artery disease. Current materials used in cardiac stents were designed for their biocompatibility, mechanical properties, and corrosion resistance. The benefits of stenting are realized within the first few months after deployment and after that time, the stent presents an inflammation and vessel obstruction hazard. For these reasons, a stent made from a biocompatible alloy that will corrode and bioabsorb into the body at a controlled and uniform rate would maximize the benefits of cardiac stenting while minimizing complication risks. Magnesium alloys seem the most promising material prospect due to the biocompatibility and high reactivity of magnesium (although this may be too high). Polarization resistance and electrochemical impedance spectroscopy experiments in a simulated body solution (Hank’s Balanced Salt Solution) were performed on existing magnesium alloys AZ31, AZ61, and AZ91 as well as innovative non equilibrium electron beam vapor deposit magnesium alloyed with titanium and yttrium. From these tests, the corrosion properties of the alloys could be evaluated. The AZ series of alloys have already been used with success as biomedical implants in clinical trials, but the presence of aluminum in the alloys remains a significant concern. The electron beam vapor deposited magnesium alloys allow higher concentrations of alloying elements in the material (which will lower the corrosion rate of magnesium) and may be the best candidate to perfect for use in bioabsorbable cardiac stents.