Developing Neural Prostheses for Spinal Injuries

Mesut Sahin, associate professor of biomedical engineering

Development of neural prostheses – devices and technologies for interfacing with the central nervous system – are the focus of research by Associate Professor Mesut Sahin.

His current project, funded by a  grant from the National Institute of Neurological Disorders and Stroke, is to develop and test a technology known as FLAMES -- floating light activated micro-electrical stimulators --for wireless activation of the central nervous system. Energized by an infrared light beam through an optical fiber located just outside the dura mater, the tough, fibrous membrane forming the outermost of the three coverings of the brain and spinal cord, these micro-stimulators allow victims of spinal cord injuries to regain self-mobility, environmental control and computer access. Sahin says this new wireless approach is an improvement over previous neural prostheses.

Electrical activation of central and peripheral nervous system has been investigated for treatment of neural disorders for many decades and a number of devices have already successfully moved into the clinical phase, such as cochlear implants and pain management via spinal cord stimulation, and others are on the  way such  as microstimulation of the spinal cord to restore locomotion; microstimulation of the cochlear nucleus, midbrain, or auditory cortex to better restore hearing; and stimulation of the visual cortex in the blind subject,” he said “But the current implantable microelectrode arrays use wired interconnects for applying the electric stimulations, and these fine wires are a major source of device failure since they are the first to break in chronic implants. The floating microstimulators will be free from any interconnects and tethering forces that would erode over time.”

FLAMES is a small device that is remotely controlled by an external unit via a near-infrared laser. The FLAMES device is implanted into the spinal cord, and is then allowed to float in the tissue with no wires attached. A patient would send the command to the external unit to activate the laser,the laser would excite the FLAMES device, which would in turn stimulate the neuron via an electrical current.

Sahin, associate professor of biomedical engineering,  in collaboration with Selim Unlu, professor of electrical and computer engineering at Boston University, are currently testing variables such as size of the device, material, voltage and placement of the device. Once FLAMES advances to the clinical stage, patients paralyzed by spinal injury will be able to regain vital functions.