A Truly Injectable Neural Stimulation Electrode Made From an In-Body Curing Polymer/Metal Composite [article]

James K. Trevathan, Ian Baumgart, Evan N. Nicolai, Brian A. Gosink, Anders J. Asp, Megan L. Settell, Shyam R. Polaconda, Kevin Malerick, Sarah K. Brodnick, Weifeng Zeng, Bruce E. Knudsen, Andrea L. McConico (+11 others)
2019 bioRxiv   pre-print
AbstractImplanted neural stimulation and recording devices hold vast potential to treat a variety of neurological conditions, but the invasiveness, complexity, and cost of the implantation procedure greatly reduce access to an otherwise promising therapeutic approach. To address this need, we have developed a novel electrode that begins as an uncured pre-polymer that is liquid and can be injected around a neuroanatomical target to minimize surgical manipulation. Referred to as the Injectrode,
more » ... e electrode conforms to complex target structures such as a foramen or plexus, and within minutes cures in vivo forming an electrically conductive interface. The resulting interface has a Young's Modulus of under 100 kPa, which is orders of magnitude less stiff than conventional electrodes. To validate the Injectrode, we performed detailed electrochemical and microscopy characterization of material properties and validated the feasibility of using it to electrically stimulate the nervous system in pre-clinical animal models. Electrochemical testing was performed based off of common FDA preclinical benchtop tests including scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient analysis. The metal particle based Injectrode within the cured silicone elastomer performed very similarly to pure wire of the same metal in all measures. Comparisons of charge storage capacity and charge injection limits of the Injectrode to mimics of the clinical LivaNova vagus nerve stimulation electrodes with the same geometric area demonstrated increased charge injection capacity, putatively resulting from the increase in fractal dimension/accessible surface area within the silicone matrix for electrochemical reaction. Acute in vivo testing of an Injectrode injected around the complex compound motor nerve branches of the brachial plexus proved low current stimulation induced tetanic activation of the terminal muscles was feasible. Finally, to establish proof of concept in an animal model better matching the scale of human anatomy, direct comparisons of the Injectrode performance to the clinical LivaNova lead were made in evoking heart rate changes via vagus nerve stimulation in swine. By virtue of being simpler than traditional electrode designs, less invasive, and more cost-effective, the Injectrode has the potential to increase the adoption of neuromodulation therapies for existing and new indications.
doi:10.1101/584995 fatcat:zujhytioznbzhacqstygyo4cti