The ability to measure brain electrical activity has allowed us to gain a better understanding of brain functions and processes over the past decade. So far, much of this activity has been measured via electrodes placed on the scalp (through electroencephalography (EEG)); however, being able to acquire signals directly from inside the brain itself (through neural interfacing devices) during daily life activities could take neuroscience and neuromedicine to completely new levels. Unfortunately, the implementation of neural interfaces has proved to be extremely difficult.
Materials used in the tiny electrodes that contact the neurons and all connectors should be flexible but strong enough to withstand the harsh environment. It has been difficult to develop long-lasting brain interfaces in the past because of the biological reactions of the body such as inflammation. What if there was a way to administer anti-inflammatory drugs locally where electrodes touch the brain?
A team of Korean researchers has developed a multifunctional brain interface that simultaneously records neuronal activity and delivers liquid drugs to the implantation site. This was published in Microsystems & Nanoengineering. Their design is flexible and different from other rigid devices. A series of microneedles gathers multiple neural signals in a given area. Thin metallic conductive lines then carry them to an external circuit. The most striking aspect of this study was the incorporation of microfluidic channels in a plane parallel with the conductive lines. This was possible by strategically stacking and micromachining polymer layers. These channels can be connected to a small reservoir that contains the drug to be administered and can carry a steady stream of liquid towards the microneedles.
Their approach was validated by brain interface experiments with live rats. Then, the team performed an analysis of drug concentrations in tissue surrounding the needles. Overall, the results are promising as Prof. Sohee Kim, Daegu Gyeongbuk Institution of Science and Technology, Korea, who led this study, comments: "The flexibility of our device will help it make it more compatible and decrease adverse effects, all which will contribute to increasing lifespan of the neural interface."
Multifunctional, durable brain interfaces have implications for many disciplines. The first author of this study, Dr. Yoo Na Kang of Korea Institute of Machinery & Materials, says that the device could be used for brain-machine interfaces. This allows paralyzed individuals to control their robotic arms and legs with their thoughts. It can also be used for neurological diseases such as electrical or chemical stimulation over many years. We hope that many people will benefit from this direct and lasting connection to the brain.