A New Approach to Metal Implants

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Cardiac and orthopedic implants offer great hope to millions of patients with blocked arteries and deteriorating joints. Some 700,000 stents are surgically implanted in patients each year. A similar number of patients receive artificial joints. But in many cases, an implant is only required for long enough for damaged tissue to heal. A metal stent or metallic bone implant that dissolved harmlessly over time would make further stenting much easier or avoid unnecessary joint surgery.

Barbara Shaw and her research associate Elzbieta Sikora have developed a process using electron beam physical vapor deposition (PVD) to create a magnesium alloy material that can be controllably and safely dissolved in the body. Vapor deposition allows them to create chemistries in the alloy that wouldn’t be possible using the more conventional methods of making alloys. Vapor deposition also allows them to get around some of the solubility issues encountered when alloys are mixed.

Perhaps most importantly, PVD allows them to control surface effects on the magnesium alloy. By manipulating the surface, coatings with drugs can be introduced, either on the surface or at different layers of the alloy. Used for orthopedic implants or coronary artery stents, these drugeluting materials could reduce the inflammation over time as the magnesium dissolves. By manipulating its composition, the alloy can be made to corrode at a predetermined rate, from weeks to a year or more in the case of certain orthopedic implants.

Barbara Shaw, Ph.D., is professor of engineering science and mechanics. Her collaborators in biomedical research include Ian Gilchrist, Henry Donahue, and Wallace Greene at Penn State Milton S. Hershey Medical Center, and departmental colleagues Steven Schiff and Bruce Gluckman in the Center for Neural Engineering. A patent is pending for the medical applications of their process.

To learn more about Barbara Shaw's research, read the Focus on Materials article Barbara Shaw Tackles Corrosion.

This research brief was featured in the brochure Biomedical Materials.