Tag Archives: surgical implants

Killer graphene spikes to kill bacteria on medical implants

Implants of all kinds (hip replacements, knee replacements, etc.) seem to be on the rise and along with that an increasing number of infections. A Swedish research team announces a technology that could make implants safer in an April 16, 2018 news item on Nanowerk,

A tiny layer of graphene flakes becomes a deadly weapon and kills bacteria, stopping infections during procedures such as implant surgery. This is the findings of new research from Chalmers University of Technology, Sweden, recently published in the scientific journal Advanced Materials Interfaces (“Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms”).

An April 16, 2018 Chalmers University of Technology press release (also on EurekAlert), which originated the news item, provides more detail about the scope of the problem and the proposed solution (Note: A link has been removed),

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 cause the implant to not attach to the skeleton, meaning it must be removed.

Bacteria travel around in fluids, such as blood, looking for a surface to cling on to. 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 bacteria to attach. Instead, bacteria are sliced apart by the sharp graphene flakes and killed. 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 grow 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.

“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. The reason is simple: one bacterium is one micrometer – one thousandth of a millimeter – in diameter, while a human cell is 25 micrometers. So, 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.

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 graphene flakes further, by coating implant surfaces and studying the effect on animal cells.

Chalmers cooperated with Wellspect Healthcare, a company which makes catheters and other medical instruments, in this research. They will now continue with a second study.

Here’s a link to and a citation for the paper,

Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms by Santosh Pandit, Zhejian Cao, Venkata R. S. S. Mokkapati, Emanuele Celauro, Avgust Yurgens, Martin Lovmar, Fredrik Westerlund, Jie Sun, Ivan Mijakovic. Advanced Materials Interfaces Volume5, Issue7 April 9, 2018 Pages 1701331 [sic] https://doi.org/10.1002/admi.201701331 First published [online]: 2 February 2018

This paper is behind a paywall.

Finally, here’s a ‘killer spikes’ video made available by Chalmers University of Technology,

‘Superhemophobic’ medical implants

Counterintuitively, repelling blood is the concept behind a new type of medical implant according to a Jan. 18, 2017 news item on ScienceDaily,

Medical implants like stents, catheters and tubing introduce risk for blood clotting and infection — a perpetual problem for many patients.

Colorado State University engineers offer a potential solution: A specially grown, “superhemophobic” titanium surface that’s extremely repellent to blood. The material could form the basis for surgical implants with lower risk of rejection by the body.

Blood, plasma and water droplets beading on a superomniphobic surface. CSU researchers have created a superhemophobic titanium surface, repellent to blood, that has potential applications for biocompatible medical devices. Courtesy: Colorado State University

A Jan. 18, 2017 Colorado State University news release by Anne Ju Manning, which originated the news item, explains more,

t’s an outside-the-box innovation achieved at the intersection of two disciplines: biomedical engineering and materials science. The work, recently published in Advanced Healthcare Materials, is a collaboration between the labs of Arun Kota, assistant professor of mechanical engineering and biomedical engineering; and Ketul Popat, associate professor in the same departments.

Kota, an expert in novel, “superomniphobic” materials that repel virtually any liquid, joined forces with Popat, an innovator in tissue engineering and bio-compatible materials. Starting with sheets of titanium, commonly used for medical devices, their labs grew chemically altered surfaces that act as perfect barriers between the titanium and blood. Their teams conducted experiments showing very low levels of platelet adhesion, a biological process that leads to blood clotting and eventual rejection of a foreign material.

Chemical compatibility

A material “phobic” (repellent) to blood might seem counterintuitive, the researchers say, as often biomedical scientists use materials “philic” (with affinity) to blood to make them biologically compatible. “What we are doing is the exact opposite,” Kota said. “We are taking a material that blood hates to come in contact with, in order to make it compatible with blood.” The key innovation is that the surface is so repellent, that blood is tricked into believing there’s virtually no foreign material there at all.

The undesirable interaction of blood with foreign materials is an ongoing problem in medical research, Popat said. Over time, stents can form clots, obstructions, and lead to heart attacks or embolisms. Often patients need blood-thinning medications for the rest of their lives – and the drugs aren’t foolproof.

“The reason blood clots is because it finds cells in the blood to go to and attach,” Popat said. “Normally, blood flows in vessels. If we can design materials where blood barely contacts the surface, there is virtually no chance of clotting, which is a coordinated set of events. Here, we’re targeting the prevention of the first set of events.”

nanotubes

Fluorinated nanotubes provided the best superhemophobic surface in the researchers’ experiments.

The researchers analyzed variations of titanium surfaces, including different textures and chemistries, and they compared the extent of platelet adhesion and activation. Fluorinated nanotubes offered the best protection against clotting, and they plan to conduct follow-up experiments.

Growing a surface and testing it in the lab is only the beginning, the researchers say. They want to continue examining other clotting factors, and eventually, to test real medical devices.

Here’s a link to and a citation for the paper,

Hemocompatibility of Superhemophobic Titania Surfaces by Sanli Movafaghi, Victoria Leszczak, Wei Wang, Jonathan A. Sorkin, Lakshmi P. Dasi, Ketul C. Popat, and Arun K. Kota. Advanced Healthcare Materials DOI: 10.1002/adhm.201600717 Version of Record online: 21 DEC 2016

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