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Argonne’s nuclear research leads to biomedical breakthrough

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Posted June 6, 2019

Pivotal discovery explains why medical implants fail.

At first glance, nuclear waste and metal hip implants seem completely unrelated. But the answers to why medical implants fail and what we can do about it may come from an unlikely source — the nuclear fuel cycle. Researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory have discovered that the same factors link the corrosion of nuclear waste forms — the packages scientists build to secure waste for millions of years — to corrosive conditions within the body that may cause implant failure.

Graduate student Eric Lee, left, and Argonne materials scientist Vineeth Kumar Gattu, right, discuss the molecular structures of metals used in medical device implants. (Image by Argonne National Laboratory.)

Graduate student Eric Lee, left, and Argonne materials scientist Vineeth Kumar Gattu, right, discuss the molecular structures of metals used in medical device implants. (Image by Argonne National Laboratory.)

Medical implants are a blessing, with artificial hips, knees, spinal discs — even teeth — allowing us to remain active and relatively pain free. Yet medical implants tend to fail more often than orthopedic surgeons expect. About 1 in 20 metal hip implants fails prematurely, according to the British medical journal The Lancet. When an implanted alloy, or combination of metals, corrodes, the aluminum, cobalt and chromium can end up in tissues and organs. They can even leach into the bloodstream, which has been linked to dementia, depression and vision loss.

Researchers at Argonne are focused on accelerating the discoveries which might lead to better outcomes.

Making the connection

In 2017, Vineeth Kumar Gattu, an Argonne materials scientist, flew to New Orleans to attend a conference devoted to corrosion research, a topic that Gattu and fellow scientist William Ebert use to establish whether nuclear waste forms they develop can withstand one million years of environmental exposure.

At the conference, Gattu learned about problems with corroding metal hip implants, finding that the materials can fail as early as seven months after surgery.

Gattu and Ebert realized that their methods for measuring how fast nuclear waste forms corrode can also be used to explain what happens to hip implants — indeed, all medical implants — after surgery.

The body electric

After surgery, metal hip implants must withstand various strains. Twisting, rubbing between pieces and upholding weight can all help corrode aluminum, cobalt and chromium. Conventional tests, Gattu found, are too short and lack the rigor needed to gauge how materials truly perform in the body.

Ideally, the hip implant material will form a barrier on its surface, which stops – or dramatically slows –corrosion. Changes in the conditions can affect the formation and stability of the barrier and the corrosion rate.

Argonne scientist Vineeth Kumar Gattu prepares a medical implant sample for corrosion testing. (Image by Argonne National Laboratory.)

“Standard methods do not predict how implants perform well enough, partly because they don’t represent the environmental conditions within the body,” said Gattu.

Scientists test for corrosion by measuring the material’s electrochemical responses to their environment. In the tests, scientists apply voltage to the material and measure the resulting electrical current. The current shows how fast the material is oxidizing, or corroding.

The problem with such tests, said Gattu, is they tend to focus on the short-term response at one voltage level, representing just one electrochemical scenario. They ignore the range of conditions that can occur within the body and corresponding changes in the material surface.

“Every biological environment has an oxidizing strength that changes with activity,” Gattu said. “You have more oxygen in the blood when you are running or walking than when you are resting. And more oxygen could drive the corrosion rate higher.”

Argonne’s William Ebert agrees. “Short-term tests may miss processes that stabilize the material’s surface, or they may miss leaching that could destabilize its surface,” said Ebert, who manages the Pyroprocess & Waste Form Development group within the laboratory’s Chemical and Fuel Cycle Technologies division. “These changes to the surface usually control the long-term corrosion behavior. We can control the conditions and directly measure the corrosion rate as the surface evolves.”

To investigate further, the Argonne team applied many voltage levels to hip implant material, sometimes for several days, much longer than standard methods require.

Indeed, the Argonne team discovered that one of the hip implant materials corroded rapidly at high voltages. “This early failure would have been predicted if researchers had conducted tests that represent the full range of possible in vivo, or in-the-body, conditions,” said Gattu.

“Standard methods do not predict how implants perform well enough, partly because they don’t represent the environmental conditions within the body.” — Vineeth Kumar Gattu, Argonne materials scientist

The road to healthier outcomesThe Argonne team continues to study hip implant material and test ideas for measuring and improving performance. The next step, said Gattu and Ebert, is to measure the effects of the strain and friction endured at the implant’s joint, known as the femoral head, which is often the first component to corrode and fail. The team is studying the benefits of metallic and ceramic coating materials to protect against both wear and corrosion to extend joint durability.

So, from the unlikely connection of studying how nuclear waste forms withstand the elements over the millennia to new pioneering discoveries of why medical devices fail may be in the offing. And these discoveries may lead to longer lasting more stable medical implants that enrich the lives of millions of people

Argonne’s new method of corrosion testing could also address gaps in other areas — wherever actual conditions affect how materials corrode. The research could have applications in measuring corrosion in water systems like those in Flint, Michigan. Other promising research areas include corrosion of auto exhaust systems, 3-D printed materials, as well as underground gas and oil pipelines.

Source: ANL

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