Spikes of graphene can kill bacteria on implants

April 16, 2018, Chalmers University of Technology
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 tiny layer of graphene flakes on a surface kills bacteria, stopping infections during procedures such as implant surgery. This is the finding of new research from Chalmers University of Technology, Sweden, recently published in Advanced Materials Interfaces.

Operations for surgical implants, such as hip and knee replacements or dental implants, have increased in recent years. However, in such procedures, there is always a risk of bacterial infection. In the worst-case scenario, this can prevent the implant from attaching to the skeleton, meaning it must be removed.

Bacteria travel in fluids such as blood, seeking to attach to a suitable surface. Once in place, they start to grow and propagate, forming a protective layer known as a biofilm. A research team at Chalmers has now shown that a layer of vertical graphene flakes forms a protective surface that makes it impossible for to attach. Instead, bacteria are sliced apart by the sharp graphene flakes and killed. Coating implants with a layer of graphene flakes can therefore 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.

Chalmers University is a leader in the area of graphene research, but the biological applications did not begin to materialise until a few years ago. The researchers saw conflicting results in earlier studies. Some showed that graphene damaged the bacteria, others that they were not affected.

The vertical flakes of graphene are not a new invention. But the Chalmers research teams are the first to use vertical graphene to kill bacteria. The next step will be to test the graphene flakes further, by coating implant surfaces and studying the effect on animal cells. Credit: Johan Bodell/Chalmers University of Technology

"We discovered that the key parameter is to orient the graphene vertically. If it is horizontal, the bacteria are not harmed," says Ivan Mijakovic, Professor at the Department of Biology and Biological Engineering.

The sharp flakes do not damage human cells because a bacterium is one micrometer in diameter, while a human cell is 25 micrometers. What constitutes a deadly knife attack for a bacterium is therefore only a tiny scratch for a human cell.

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

Chalmers University is a leader in the area of graphene research, but did not start to study the biological applications until a couple of years ago. Now the researchers believe that graphene shows great potential for different healthcare applications. "Something else that's becoming big, and I think is going to be very important in the future, is so-called 'biosensing'. Graphene conducts electricity, which means it can be used to detect problems in the body, such as bacterial problems, cancer, or elevated glucose levels. It gives us a whole new way of preventing health problems," says Chalmers Professor Ivan Mijakovic. Credit: Johan Bodell/Chalmers University of Technology

Good bacteria are also killed by the graphene. But that's not a problem, as the effect is localised and the balance of microflora in the body remains undisturbed. "We want to prevent bacteria from creating an infection. Otherwise, you may need antibiotics, which could disrupt the balance of normal bacteria and also enhance the risk of antimicrobial resistance by pathogens," says Santosh Pandit, postdoc at Biology and Biological Engineering.

Vertical flakes of graphene are not a new invention, having existed for a few years. But the Chalmers research teams are the first to use the vertical graphene in this way. The next step for the research team will be to test the further by coating surfaces and studying the effect on animal cells.

The making of vertical graphene

Graphene is made of carbon atoms. It is only a single atomic layer thick, and therefore the world's thinnest material. Graphene is made in flakes or films. It is 200 times stronger than steel, and has very good conductivity thanks to its rapid electron mobility. Graphene is also extremely sensitive to molecules, which allows it to be used in sensors.

Graphene can be made by chemical vapor deposition (CVD). The method is used to create a thin surface coating on a sample. The sample is placed in a vacuum chamber and heated to a high temperature. Simultaneously, three gases, usually hydrogen, methane and argon,are released into the chamber. The high heat causes gas molecules to react with each other, and a thin layer of is created.

To produce vertical forms, researchers use a process known as plasma-enhanced (PECVD). Then, an a plasma is applied over the sample, which causes the gas to be ionized near the surface. With the plasma, the layer of carbon grows vertically from the surface, instead of horizontally as with CVD.

Explore further: New insights on graphene

More information: Santosh Pandit et al, Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms, Advanced Materials Interfaces (2018). DOI: 10.1002/admi.201701331

Related Stories

New insights on graphene

December 21, 2017

Graphene floating on water does not repel water, as many researchers believe, but rather attracts it. This has been demonstrated by chemists Liubov Belyaeva and Pauline van Deursen and their supervisor Grégory F. Schneider. ...

Scientists produce graphene using microorganisms

March 22, 2012

The Graphene Research Group at Toyohashi University of Technology (Japan) reports on the synthesis of graphene by reducing graphene oxide using microorganisms extracted from a local river.

Flaky graphene makes reliable chemical sensors

January 17, 2012

Scientists from the University of Illinois at Urbana-Champaign and the company Dioxide Materials have demonstrated that randomly stacked graphene flakes can make an effective chemical sensor.

Graphene on silicon carbide can store energy

May 23, 2017

By introducing defects into the perfect surface of graphene on silicon carbide, researchers at Linköping University in Sweden have increased the capacity of the material to store electrical charge. This result, which has ...

Travelling through the body with graphene

September 28, 2016

For the first time researchers succeeded to place a layer of graphene on top of a stable fatty lipid monolayer. Surrounded by a protective shell of lipids graphene could enter the body and function as a versatile sensor. ...

Recommended for you

Study sheds light on—and through—2-D materials

September 24, 2018

The ability of metallic or semiconducting materials to absorb, reflect and act upon light is of primary importance to scientists developing optoelectronics—electronic devices that interact with light to perform tasks. Rice ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.