In recent years, the number of patients receiving surgical implants – including hip and knee replacements or dental implants – has been on the rise. While these procedures are well established and usually successful, surgeons can run into problems relating to bacterial infection.
Bacteria can be transported within bodily fluids and grow and multiply on a surface. This mass of microorganisms, stuck to each other and to the surface, forms a layer known as a biofilm.
The growth of a biofilm on a surgical implant can prevent the implant from adhering to the bone through osseointegration: the process in which bone cells grow into the implant, fusing them together. This results in the implant having to be removed with further invasive surgery.
Now, a team of biological engineers based at Chalmers University has demonstrated that a layer of graphene flakes can be used as a protective surface for implants. As bacteria approach the surface, they are sliced apart by the sharp, vertical flakes and are killed. Graphene – an atom thick layer of carbon atoms – is known for its extraordinary properties, such as its strength and excellent electrical and thermal conductivity.
These graphene flakes do not damage human cells, due to human cells tending to be far larger than bacteria, although they do kill good bacteria in the region surrounding the implant.
"We discovered that the key parameter is to orient the graphene vertically,” said Professor Ivan Mijakovic, who leads a laboratory at Chalmers’ department of biology and biological engineering. “If it is horizontal, the bacteria are not harmed.”
The researchers hope that this coating could help protect patients against bacterial infection following surgery, lowering the possibility that their implants will be rejected and preventing the need to take antibiotics (which contribute to the looming risk of antibiotic resistance).
The graphene surface has even been demonstrated to encourage the process of osseointegration.
This is the first such use of vertical graphene flakes, and according to the researchers, more research is necessary before this graphene surface could be used for regular hip replacements and other operations. Next, the researchers will be coating implants with these graphene spikes and studying their effect in animal models.