A step closer to safe nano-electrodes in the brain

02 October 2011

The biological safety of nanotechnology, i.e. how the body reacts to nanoparticles, is a hot topic. Researchers at Lund University have now, for the first time, conducted successful trials of injected ‘nanowires’.

In the future, it is expected that it will become possible to implant electrodes built on the nanoscale in order to study learning and memory and to treat patients who are suffering from chronic pain, depression and diseases such as Parkinson’s. However, no-one knows how the brain would react if the electrodes were to come loose from their supports.

For the first time, researchers at Lund University have investigated this ‘worst case scenario’ by injecting ‘nanowires’, or registration points, which have the same size and design as the future electrodes’ supports, into the brains of rats. The results show that the brain’s ‘cleaning cells’, microglia, deal with the wires. After twelve weeks, only minor differences could be observed between the brains of the test group and the control group. The results were published in the journal Nano Letters.

“The results indicate that this is a viable way to proceed. We now have a better basis on which to develop more advanced and more useful electrodes than those currently available”; explains Christelle Prinz, a researcher in Solid State Physics at the Faculty of Engineering at Lund University, who together with Cecilia Eriksson Linsmeier at the Faculty of Medicine is the principal author of the article ‘Nanowire Biocompatibility in the Brain – Looking for a Needle in a 3D Stack’.

Electrodes are already used to combat symptoms of Parkinson’s disease, for example. Future nanotechnology could make a refined and improved treatment possible and open the way for entirely new fields of application.

One advantage of nano-sized electrodes is that the smallest components of the brain can be monitored and stimulated. In order to study the biological safety of the technology (biocompatibility), the researchers first manufactured nanowires, which were then suspended in a liquid which was injected into the brains of the rats. The same number of rats received a solution without nanowires. After one, six and 12 weeks, the reaction of the rats’ brains to the nanowires was studied.

The research project is run by the University’s interdisciplinary Neuronano Research Centre (NRC), coordinated by Jens Schouenborg at the Faculty of Medicine with financing from Linnaeus grants and the Wallenberg Foundation. The project has involved researchers from both the Faculty of Medicine and the Nanometre Structure Consortium, which is headed by Lars Samuelson at the Faculty of Engineering.

“We studied two of the brain tissue’s support cells, microglia cells, which are responsible for ‘cleaning up’ waste and infectious substances in the brain, and astrocytes, which help in the brain’s healing processes. The microglia cells ‘ate’ most of the nanowires. In weeks 6 and 12 we could see remnants of them in the microglia cells”, says Nils Danielsen, a researcher at NRC.

The number of nerve cells remained constant all the time, which is a positive sign. The largest difference between the test and control groups was that the former had a more significant astrocyte reaction in the first week, but the level fell gradually. In weeks 6 and 12 the researchers could see no difference at all.

“Together with the other results and in the light of the fact that the number of microglia cells fell over time, the results suggest that the brain is not damaged and does not suffer any chronic effects of the nanowires”, concludes Christelle Prinz.

Authors of ‘Nanowire biocompatibility in the brain – looking for a needle in a three-dimensional stack’: Cecilia Linsmeier Eriksson, Christelle N. Prinz, Lina M. E. Pettersson, Philippe Caroff, Lars Samuelson, Jens Schouenborg, Lars Montelius, Nils Danielsen.

Link to abstract in Nano Letters journal