Improved Brain Implants Could Help Control Neuronal Networks

A new type of nanowire material might improve the longevity of neuroprosthetic brain implants used to treat Parkinson’s disease (PD) and other neurological diseases.

The new nanowires, developed by researchers at Lund University (Sweden), are made from gallium phosphide, where each outgrowing nanowire has a diameter of only 80 nanometers. The dense array of vertical nanowires is intercalated with flat surface regions to separate retinal neurons and glial cells into distinct, but neighboring, compartments. Thus, while neurons grow and extend processes on the nanowires, the glial cells primarily occupy the flat regions in between.

According to the researchers, the need for the new nanowires results from several severe drawbacks associated with current implants. One problem is that the body interprets the implants as foreign objects, resulting in an encapsulation of the electrode, which in turn leads to loss of signal. Another problem is that in neural cultures, glial cells tend to overgrow neurons, limiting access to neuronal interrogation. There is therefore a pressing need for improved systems that enable a good separation when co-culturing neurons and glial cells simultaneously.

Besides use as brain implants for PD and other neurological deficits, the researchers have also developed a nanowire patterning capable of guiding optic nerve axons, which could be used as retinal implants able to replace light-sensitive cells that die in cases of Retinitis Pigmentosa and other eye diseases. The neural implants can be used in many other areas as well, such as in treating depression, severe cases of autism, obsessive-compulsive disorders, and paralysis. The study describing the new nanowires was published on August 11, 2015, in ACS Applied Materials and Interfaces.

“I was very pleasantly surprised by these results; in previous in vitro experiments, the glial cells usually attach strongly to the electrodes”, said senior author Christelle Prinz, PhD, a researcher in Nanophysics at Lund University. “Our nanowire structure prevents the cells that usually encapsulate the electrodes from doing so. The different types of cells continue to interact; this is necessary for the neurons to survive because the glial cells provide them with important molecules.”

Neuronal survival and function are greatly dependent on glial cell support, and even in vitro glial cells control the number of synapses and increase the synaptic efficacy in neuronal cultures. Direct proximity of neurons to glial cells has also been shown to be necessary to support long-term potentiation, a mechanism that underlies learning and memory. Thus, to ensure that cultured neurons behave as closely as possible to neurons in the in vivo situation, it is important that they are cultured together with glial cells.

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