Abstract
Reliably interfacing a nerve with an electrode array is one of the approaches to restore motor and sensory functions after an injury to the peripheral nerve. Accomplishing this with current technologies is challenging as the electrode-neuron interface often degrades over time, and surrounding myoelectric signals contaminate the neuro-signals in awake, moving animals. The purpose of this study was to evaluate the potential of microchannel electrode implants to monitor over time and in freely moving animals, neural activity from regenerating nerves. We designed and fabricated implants with silicone rubber and elastic thin-film metallization. Each implant carries an eight-by-twelve matrix of parallel microchannels (of 120 × 110 μm2 cross-section and 4 mm length) and gold thin-film electrodes embedded in the floor of ten of the microchannels. After sterilization, the soft, multi-lumen electrode implant is sutured between the stumps of the sciatic nerve. Over a period of three months and in four rats, the microchannel electrodes recorded spike activity from the regenerating sciatic nerve. Histology indicates mini-nerves formed of axons and supporting cells regenerate robustly in the implants. Analysis of the recorded spikes and gait kinematics over the ten-week period suggests firing patterns collected with the microchannel electrode implant can be associated with different phases of gait.
Highlights
Fibers and in the access and surgical placement of the electrode next to the nerve, especially small visceral nerves[8]
Microchannel electrode implants were prepared with soft MEMS microfabrication techniques
The implant fabrication process includes three main steps (Fig. 1B): (1) molding of 8 PDMS microchannel layers against PDMS negative molds, (2) patterning of two thin-metal film microelectrode arrays embedded in PDMS membrane (Fig. 1C), and (3) alignment and plasma-bonding of the 12 elastomeric layers
Summary
Fibers and in the access and surgical placement of the electrode next to the nerve, especially small visceral nerves[8]. The quality of the recordings often degrades over time as foreign body reaction may trigger electrode encapsulation, and the nerve moves with respect to the electrode sites in chronic settings With these observations in mind, we have designed and manufactured a nerve implant, which exploits the natural properties of the peripheral nerve to regenerate and offers spatially distributed electrodes for efficient axon-electrode coupling. Regenerative microchannel electrodes are essentially “long” sieve implants that host millimeter length of the nerve[19,20,21] In this design, the nerve regenerates in parallel “mini-nerves” - bundles of axons accompanied with blood vessels in each microchannel. This results in a significant rise of the recordable extracellular amplitude (Vout) of the action potential as
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