[Image above] Credit: Niels Kliim; Flickr CC BY 2.0
When it comes to biomedical implants, choosing appropriate materials so that the body can interact with them—such as coatings composed of phosphate glass fibers—is just part of the equation for successful biointegration. Another critical consideration is how to prevent bacterial growth on said implant.
Infection, not mechanical failure, actually is a leading cause of overall failure of medical devices. And with rising resistance of bacteria to known antibacterial agents, the problem will only continue to get worse.
Researchers at Chalmers University of Technology (Göteborg, Sweden) may have a nanomaterials solution, however—they have devised a way to contract graphene to do the killing, using a thin layer of atomically thin graphene spikes to slice bacteria apart.
“We discovered that the key parameter is to orient the graphene vertically. If it is horizontal, the bacteria are not harmed” Ivan Mijakovic, professor at the Department of Biology and Biological Engineering, says in a Chalmers University news release.
Credit: Chalmers University of Technology; YouTube
To get the graphene to stand tall, the team used plasma-enhanced chemical vapor deposition to fabricate surfaces of vertically oriented graphene spikes. In the process, plasma causes gas to ionize near the surface, prompting the carbon layer to grow vertically in spikes that stretch 60–100 nm off the surface.
And while those spikes basically rip apart bacteria when they come in contact, the spikes are harmless to human cells thanks to the large cell size differential between the two—while bacterial cells are on the order of ~1 µm in diameter, human cells are more like ~25µm wide (of course, different types of cells differ in size). So what’s a huge machete to a bacterium is more like a harmless pinprick to a human cell.
The size differential allows graphene spikes to slice bacteria apart, while leaving far larger human cells undamaged. Credit: Yen Strandqvist; Chalmers University of Technology
Although the concept is promising so far, the team has several important questions to answer before graphene spikes are found on your next knee replacement hardware—including how the graphene spikes interact with the body and how they fare over longterm exposure within the body.
“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” Jie Sun, associate professor at the Department of Micro Technology and Nanoscience, says in the release.
The paper, published in Advanced Materials Interfaces, is “Vertically aligned graphene coating is bactericidal and prevents the formation of bacterial biofilms” (DOI: 10.1002/admi.201701331).
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