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Vertical graphene flakes form a protective surface that makes it impossible for bacteria to attach. Instead, bacteria are sliced apart by the sharp graphene flakes and killed. Human cells volume is typically 15,000 times larger. So, what constitutes a deadly knife attack for a bacterium, is therefore only a tiny scratch for a human cell. Coating implants with a layer of graphene flakes can therefore help protect the patient against infection, eliminate the need for antibiotic treatment, and reduce the risk of implant rejection. The osseointegration - the process by which the bone structure grows to attach the implant -- is not disturbed. In fact, the graphene has been shown to benefit the bone cells. Credit: Yen Strandqvist/Chalmers University of Technology

A small layer of graphene flakes or spike could help improve the overall safety and success of implant surgeries.

Researchers from Chalmers University of Technology have discovered that the small layer of vertical graphene flakes kills bacteria and stops infections during procedures like hip and knee replacements.

Implant surgeries come with a risk for bacterial infection, which can cause the implant to not attach to the skeleton and require removal. Bacteria can travel around in blood, looking to cling to surfaces and once they begin to grow and propagate, they form a protective layer called a biofilm.

The researchers discovered that a layer of vertical graphene flakes could form a protective surface that makes it impossible for the bacteria to attach. The bacteria is ultimately sliced apart by the sharp graphene flakes and killed.

By coating implants with the graphene, surgeons can protect the patient against infection, eliminate the need for antibiotic treatment and reduce the risk of implant rejection.

“We discovered that the key parameter is to orient the graphene vertically,” Ivan Mijakovic, a professor at the Department of Biology and Biological Engineering, said in a statement. “If it is horizontal, the bacteria are not harmed.”

While good bacteria is also killed by the graphene, the effect is localized and the balance of microflora in the body remains undisturbed.

“We want to prevent bacteria from creating an infection,” Santosh Pandit, a postdoc in the Department of Biology and Biological Engineering, said in a statement. “Otherwise, you may need antibiotics, which could disrupt the balance of normal bacteria and also enhance the risk of antimicrobial resistance by pathogens.”

The graphene do not harm human cells because one bacterium is just one micrometer in diameter while a human cell is 25 micrometers.

By keeping the height of the vertical graphene coating between 60 and 100 nanometers, the coating is able to effectively kill bacteria, while being completely harmless to mammalian cells.

“Graphene has high potential for health applications,” Jie Sun, an associate professor at the Department of Micro Technology and Nanoscience, said in a statement. “But more research is needed before we can claim it is entirely safe. Among other things, we know that graphene does not degrade easily.”

Vertical graphene is produced through a process called Plasma-Enhanced Chemical Vapor Deposition. An electric field or plasma is then applied over the sample to cause the gas to be ionized near the surface.

The researchers now plan to test the graphene flakes by coating implant surfaces and studying the effect on animal cells.

The study was published in Advanced Materials Interfaces.

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