A Subdural Bioelectronic Implant to Obtain Recordings of Spinal Cord Activity and to Deliver Electroceutical Therapy Following Spinal Cord Injury in Rats

Bioelectronic devices have found use at the interface with neural tissue to investigate and treat nervous system disorders. We have developed and characterized a very thin flexible polyimide-based bioelectronic implant that is inserted along the thoracic spinal cord in rats directly in contact with the dorsal surface of the spinal cord. This has no negative impact on hind-limb functionality nor any change in the volume or shape of the spinal cord. We routinely maintain the bioelectronic implant in rats for a period of 3 months.<br/>We have obtained the first subdural recordings of spinal cord activity in freely moving animals. Recordings contain action potentials from fibre tracks in the cord. Following spike extraction propagation velocities were analyzed. Propagation was predominately in the afferent direction, with a smaller proportion of spikes propagating in the efferent direction.<br/>A clinically relevant spinal contusion injury can be achieved with the implant in place. The bioelectronic implant contains stimulating electrodes with relatively larger areas than the recording electrodes that are capable of delivering precise, strong electric field therapies (electroceuticals) directly to the injured spinal cord tissue. The effects of these therapies are currently being investigated, early data is demonstrating a different recovery profile compared to control animals who do not receive the treatment. Over the course of the 12-week experiment, the animals receiving electroceutical therapy show improved hind limb function determined in open field assessment and an enhanced recovery of touch sensitivity as determined by the Von Frey test.<br/>This device has great potential to monitor electrical signaling in the spinal cord after an injury, and in the future, this implant will facilitate the identification of biomarkers in spinal cord injury and recovery. We are exploring further development of this implant to deliver localized treatments to the spinal cord towards regeneration of damaged tissues to recover lost function. Localized therapies are being developed not only in the form of electroceutical treatment through precise electrical field stimulation, but also through the local and sustained delivery of neurotrophic factors.