Posts tagged neural implants
Articles and news from the latest research reports.
Silicon-based probe microstructure could underpin safer neural implants
Neural probe arrays are expected to significantly benefit the lives of amputees and people affected by spinal cord injuries or severe neuromotor diseases. By providing a direct route of communication between the brain and artificial limbs, these arrays record and stimulate neurons in the cerebral cortex.
(Image caption: The compact neural probe array consists of a three-dimensional probe array, a custom 100-channel neural recording chip and a flexible polyimide polymer cable. Credit: A*STAR Institute of Microelectronics)
The need for neural probe arrays that are compact, reliable and deliver high performance has prompted researchers to use microfabrication techniques to manufacture probe arrays. Now, a team led by Ming-Yuan Cheng from the A*STAR Institute of Microelectronics, Singapore, has developed a three-dimensional probe array for chronic and long-term implantation in the brain. This array is compact enough to freely float along with the brain when implanted on the cortex.
The neural probe array needs to be implanted in the subarachnoid space of the brain, a narrow region of 1–2.5 millimeters in depth that lies between the pia mater and dura mater brain meninges. “A high-profile array may touch the skull and damage the tissue when relative micromotions occur between the brain and the probes,” explains Cheng. To avoid this problem, the array should be as thin as possible.
(Image caption: This image shows a PC12 cell growing onto a randomly textures surface. Note how the cell is spreading out in all directions.)
Surface Characteristics Influence Cellular Growth on Semiconductor Material
Changing the texture and surface characteristics of a semiconductor material at the nanoscale can influence the way that neural cells grow on the material.
The finding stems from a study performed by researchers at North Carolina State University, the University of North Carolina at Chapel Hill and Purdue University, and may have utility for developing future neural implants.
“We wanted to know how a material’s texture and structure can influence cell adhesion and differentiation,” says Lauren Bain, lead author of a paper describing the work and a Ph.D. student in the joint biomedical engineering program at NC State and UNC-Chapel Hill. “Basically, we wanted to know if changing the physical characteristics on the surface of a semiconductor could make it easier for an implant to be integrated into neural tissue – or soft tissue generally.”
The researchers worked with gallium nitride (GaN), because it is one of the most promising semiconductor materials for use in biomedical applications. They also worked with PC12 cells, which are model cells used to mimic the behavior of neurons in lab experiments.
In the study, the researchers grew PC12 cells on GaN squares with four different surface characteristics: some squares were smooth; some had parallel grooves (resembling an irregular corduroy pattern); some were randomly textured (resembling a nanoscale mountain range); and some were covered with nanowires (resembling a nanoscale bed of nails).
Very few PC12 cells adhered to the smooth surface. And those that did adhere grew normally, forming long, narrow extensions. More PC12 cells adhered to the squares with parallel grooves, and these cells also grew normally.
About the same number of PC12 cells adhered to the randomly textured squares as adhered to the parallel grooves. However, these cells did not grow normally. Instead of forming narrow extensions, the cells flattened and spread across the GaN surface in all directions.
More PC12 cells adhered to the nanowire squares than to any of the other surfaces, but only 50 percent of the cells grew normally. The other 50 percent spread in all directions, like the cells on the randomly textured surfaces.
“This tells us that the actual shape of the surface characteristics influences the behavior of the cells,” Bain says. “It’s a non-chemical way of influencing the interaction between the material and the body. That’s something we can explore as we continue working to develop new biomedical technologies.”
![Building Better Brain Implants: The Challenge of Longevity
On August 20, JoVE, the Journal of Visualized Experiments will publish a technique from the Capadona Lab at Case Western Reserve University to accommodate two challenges inherent in brain-implantation technology, gauging the property changes that occur during implantation and measuring on a micro-scale. These new techniques open the doors for solving a great challenge for bioengineers — crafting a device that can withstand the physiological conditions in the brain for the long-term.
“We created an instrument to measure the mechanical properties of micro-scale biomedical implants, after being explanted from living animals,” explained the lab’s principal investigator, Dr. Jeffrey R. Capadona. By preserving the changing properties that occurred during implantation even after removal, the technique offers potential to create and test new materials for brain implant devices. It could result in producing longer lasting and better suited devices for the highly-tailored functions.
For implanted devices, withstanding the high-temperatures, moisture, and other in-vivo properties poses a challenge to longevity. Resulting changes in stiffness, etc, of an implanted material can trigger a greater inflammatory response. “Often, the body’s reaction to those implants causes the device to prematurely fail,” says Dr. Capadona, “In some cases, the patient requires regular brain surgery to replace or revise the implants.”
New implantation materials may help find solutions to restore motor function in individuals who have suffered from spinal cord injuries, stroke or multiple sclerosis. “Microelectrodes embedded chronically in the brain could hold promise for using neural activity to restore motor function in individuals who have, suffered from spinal cord injuries,” said Dr. Capadona.
Furthermore, Capadona and his colleagues’ method allows for measurement of mechanical properties using microsize scales. Previous methods typically require large or nano-sized samples of material, and data has to be scaled, which doesn’t always work.
When asked why Dr. Capadona and his colleagues published their methods with JoVE, he responded “We choose JoVE because of the novel format to show readers visually what we are doing. If a picture is worth [a] thousand words, a video is worth a million.”](http://41.media.tumblr.com/339c082c16372e9e4ff44d3f5528261e/tumblr_mrupbokuzM1rog5d1o1_500.png)
Building Better Brain Implants: The Challenge of Longevity
On August 20, JoVE, the Journal of Visualized Experiments will publish a technique from the Capadona Lab at Case Western Reserve University to accommodate two challenges inherent in brain-implantation technology, gauging the property changes that occur during implantation and measuring on a micro-scale. These new techniques open the doors for solving a great challenge for bioengineers — crafting a device that can withstand the physiological conditions in the brain for the long-term.
“We created an instrument to measure the mechanical properties of micro-scale biomedical implants, after being explanted from living animals,” explained the lab’s principal investigator, Dr. Jeffrey R. Capadona. By preserving the changing properties that occurred during implantation even after removal, the technique offers potential to create and test new materials for brain implant devices. It could result in producing longer lasting and better suited devices for the highly-tailored functions.
For implanted devices, withstanding the high-temperatures, moisture, and other in-vivo properties poses a challenge to longevity. Resulting changes in stiffness, etc, of an implanted material can trigger a greater inflammatory response. “Often, the body’s reaction to those implants causes the device to prematurely fail,” says Dr. Capadona, “In some cases, the patient requires regular brain surgery to replace or revise the implants.”
New implantation materials may help find solutions to restore motor function in individuals who have suffered from spinal cord injuries, stroke or multiple sclerosis. “Microelectrodes embedded chronically in the brain could hold promise for using neural activity to restore motor function in individuals who have, suffered from spinal cord injuries,” said Dr. Capadona.
Furthermore, Capadona and his colleagues’ method allows for measurement of mechanical properties using microsize scales. Previous methods typically require large or nano-sized samples of material, and data has to be scaled, which doesn’t always work.
When asked why Dr. Capadona and his colleagues published their methods with JoVE, he responded “We choose JoVE because of the novel format to show readers visually what we are doing. If a picture is worth [a] thousand words, a video is worth a million.”