UC researcher studies dissolving medical implants
Patients with broken bones sometimes need steel plates and screws to heal properly. But what happens to all that metal once the bone heals?
Walk through a metal detector, and they have their answer.
A researcher at the University of Cincinnati is studying a single-crystal magnesium implant that dissolves in the body. With these devices, people can avoid long-term complications and surgeries that arise from conventional metal implants.
“Single-crystal magnesium is a unique material that has a combination of excellent mechanical properties,” UC professor Vesselin Shanov said. “In the body, magnesium dissolves or biodegrades slowly without any side effects and is then excreted.”
UC Professor of Chemical Engineering Vesselin Shanov studies magnesium-based medical implants that dissolve in the body. He was inducted Monday into the American Institute for Medical and Biological Engineering's College of Fellows. Photo/Corrie Stookey/CEAS Marketing
The American Institute for Medical and Biological Engineering inducted Shanov to its College of Fellows this week. The College of Fellows comprises the top 2 percent of medical and biological engineers and distinguishes those who pioneer new and developing fields of technology.
The honor reflects the innovation agenda platform of UC’s strategic direction, Next Lives Here.
Shanov’s work in magnesium-based medical application, with collaboration from the University of Pittsburgh and University of North Carolina A&T, is part of a 10-year, $24 million National Science Foundation grant for the Engineering Research Center for Revolutionizing Metallic Biomaterials.
UC professor Vesselin Shanov has been fabricating magnesium-based medical implants as part of a grant funded by the National Science Foundation. He has increased the size of the implants and hopes to eventually apply them to humans. Photo/Corrie Stookey/CEAS Marketing
For adults, stainless steel plates and screws can stay in the body forever but, for children, secondary surgery is often needed. After a child’s bone heals, the bone continues to grow, but the implanted metal plates cannot bend or extend and must be removed.
“It’s a huge trauma to bring the kid back to the surgical room for secondary surgery just to unscrew and take [the plates],” said Shanov, a professor of chemical engineering in UC's College of Engineering and Applied Science.
Other researchers have used magnesium for biomedical implants, but Shanov and the team are the first to use single-crystal magnesium. Single-crystal structures are more flexible than polycrystalline ones, which is what some hospitals in Europe use for implants.
Shanov’s work with magnesium doesn’t end with plates and screws, though. He’s also applying the technology to one of the body’s most vital organs.
The stent and the heart
UC Vesselin Shanov inspects several magnesium-based stents. These stents can be implanted in arteries, provide a stable structure that opens up the arteries and then dissolve after several months. Photo/Corrie Stookey/CEAS Marketing
When people age, their arteries narrow because of the buildup of plaque on the artery’s walls. If enough plaque builds up, it can clog the artery and prevent enough blood from reaching the heart. To expand these passageways, a surgeon can place a stent, or a small, hollowed cylinder, in the artery.
The problem is that these stents are made of stainless steel or other alloys that are strong and permanent. Among other complications, the same plaque that built up on the initial artery wall can eventually build up on the wall of the stent.
But what if these stents were made of magnesium?
“Imagine that the stent does the job, recuperates the blood vessel, but then in a few months, it disappears,” said Shanov.
Shanov and two other researchers, UC professor of mechanical engineering Mark Schulz and University of Arizona professor of medicine Prabir Roy-Chaudhury, are now making stents out of magnesium. Their stents are the first magnesium stents in the world made with a process called photochemical etching.
Imagine that the stent does the job, recuperates the blood vessel, but then in a few months, it disappears.
Vesselin Shanov, UC professor
UC professor Vesselin Shanov instructs one of his students in the lab, materials science Ph.D. student Guangqi Zhang. The machine they are using can be used to design patterns for photochemical etching. Photo/Corrie Stookey/CEAS Marketing
In conventional technologies, manufacturers use lasers to create tiny structures out of magnesium-based cylinders. This process can be an expensive and slow process, whichcan reduce its commercial feasibility.
Instead, Shanov is using a faster, less expensive option that uses photolithography, a common process in the semiconductor industry that uses light and a photo-sensitive polymer to transfer a pattern onto a material. Rather than start the process with cylinders, Shanov starts with thin magnesium sheets.
Think of photolithography like playing with chemical shadow puppets.
First, you dip a magnesium sheet into a light-sensitive polymer. Then, you place a computer-generated photo-mask between the light and the magnesium sheet. The light that passes through the mask casts the pattern onto the polymer-coated sheet. Depending on the polymer, the light either makes the polymer soluble or insoluble. Finally, you use a solvent to remove the soluble part of the polymer and use an acid to etch out the magnesium sheet from the created pattern.
UC professor Vesselin Shanov and his students have created several designs for stents through a process called photochemical etching. The process, which uses light to etch designs into thin sheets of magnesium, is more commercially viable than conventional laser-cutting technologies. Photo/Corrie Stookey/CEAS Marketing.
UC professor Vesselin Shanov talks about some of the magnesium-based research that has been published at UC. Photo/Corrie Stookey./CEAS Marketing
The result is a patterned sheet of magnesium. All that’s left is to roll it up and weld it together with a laser, and you have a stent.
“This way we don’t need to use a laser to cut individually each feature of the stent pattern. We can do it in big sheets, thus creating multiple stent structures at once” said Shanov. “It’s probably 300 percent cheaper when comparing it to conventional laser cutting.”
This technology in producing stents is protected by a U.S. patent and has been tested successfully in animal models.
Shanov and his collaborators are now on the final year of the grant from the National Science Foundation. The two magnesium-based products are still in the academic setting, but Shanov hopes that the team can eventually bring them to market.
Wherever this research goes, Shanov and the team have shown the many exciting possibilities for magnesium-based applications. Long-term complications from broken bones or clogged arteries may, like magnesium implants, eventually dissolve.
Featured image at top: UC professor Vesselin Shanov discusses one of his magnesium-based medical products: a thin sheet of magnesium that can be rolled and welded into a stent. Shanov's research has been part of a 10-year $24 million grant by the National Science Foundation. Photo/Corrie Stookey/CEAS Marketing
UC professor Vesselin Shanov and graduate student Guangqi Zhang pose in the lab. Photo/Corrie Stookey/CEAS Marketing
Next Lives Here
Students and professors at the University of Cincinnati work in innovative and impactful ways. The innovation agenda is one of three platforms of UC's strategic direction, Next Lives Here.
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