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3D-printed metal implant kills bacteria to fight infection

Professional Engineering

The 3D-printed material's resistance to fatigue is tested (Credit: WSU Photo Services)
The 3D-printed material's resistance to fatigue is tested (Credit: WSU Photo Services)

A 3D-printed metal implant killed 87% of the bacteria that cause staph infections while remaining strong and compatible with surrounding tissue, according to its developers.

The novel surgical implant, developed by researchers at Washington State University (WSU), could one day lead to better infection control in common surgeries. Bacterial colonisation is a lead cause of failure for hip and knee replacements, and can lead to bad outcomes after surgery.

“Infection is a problem for which we do not have a solution,” said Amit Bandyopadhyay, corresponding author of a new paper on the work. “In most cases, the implant has no defensive power from the infection. We need to find something where the device material itself offers some inherent resistance – more than just providing drug-based infection control… why not change the material itself and have inherent antibacterial response from the material?”

Titanium materials used for hip and knee replacements and other surgical implants were developed more than 50 years ago and are not well suited to overcoming infections, the researchers said.

Although surgeons often treat pre-emptively with antibiotics, life-threatening infections can occur shortly after surgery or weeks or months later as a secondary infection. Once an infection sets in as a fuzzy, fine film on an implant, doctors try to treat it with systemic antibiotics. In about 7% of implant surgery cases, however, doctors have to perform a revision surgery – removing the implant, cleaning the area, adding antibiotics and putting in another implant.

The WSU researchers used laser powder bed fusion to add 10% tantalum, a corrosion-resistant metal, and 3% copper to the titanium alloy typically used in implants. When bacteria came into contact with the 3D-printed material’s copper surface, almost all of their cell walls ruptured.

The tantalum encouraged healthy cell growth of surrounding bone and tissue, speeding up the healing process, the researchers added.

The team spent three years on a comprehensive study of their implant, assessing its mechanical properties and biological and antibacterial response both in the lab and in animal models. They also studied its wear to make sure that metal ions from the implant will not wear off and move into nearby tissue, causing toxicity.

“The biggest advantage for this type of multifunctional device is that one can use it for infection control as well as for good bone tissue integration,” said co-author Susmita Bose. “Because infection is such a big issue in today’s surgical world, if any multifunctional device can do both things, there’s nothing like it.”

The researchers are continuing the work, hoping to improve the bacterial death rate to the standard of more than 99%, without compromising tissue integration. They also want to make sure that the materials offer good performance under real-world loading conditions that patients might use – such as hiking, in the case of a knee replacement.

The team aims to commercialise the work and has filed a provisional patent. The work was funded by the US National Institutes of Health and included collaboration with researchers from Stanford University and WSU’s College of Veterinary Medicine.

The work was reported in the International Journal of Extreme Manufacturing

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.


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