Modeling the Recording of Intraneural Action Potentials with Microelectrodes Using FEM and Point-Source Methods

et al. 2021

Preprint

ObjectiveBioelectric medicine offers therapeutic diagnoses and treatments for disorders of the nervous system unresponsive to pharmacological treatments. While current neural interfaces effectively treat many disorders with stimulation, recording specificity is often limited to gross averages across many neurons or axons. Here, we develop and describe a novel, robust carbon fiber electrode array adaptable to many neural structures for precise neural recording.ApproachCarbon fibers were sharpened using a blowtorch method made reproducible by using the reflection of fibers against the surface of a water bath. Arrays of carbon fibers were developed by partially embedding carbon fibers in medical-grade silicone to improve robustness to fracture. Acute spontaneous electrophysiology was recorded from the rat cervical vagus nerve, feline dorsal root ganglia, and rat brain. Acute brushing and bladder pressure electrophysiology was recorded from feline dorsal root ganglia as well.Main resultsBlowtorching resulted in fibers of 72.3 ± 33.5 degree tip angle with 146.8 ± 17.7 μm exposed carbon. Silicone-embedded carbon fiber arrays were robust to bending (87.5% of fibers remained unbroken, 50,000 passes). Observable neural clusters were recorded using sharpened carbon fiber electrodes from rat cervical vagus nerve (41.8 μVpp, N=3 electrodes), feline dorsal root ganglia (101.1 μVpp, N=32 electrodes), and rat brain (80.7 μVpp, N=7 electrodes). Recordings from the feline dorsal root ganglia included physiologically-relevant signals from increased bladder pressure and cutaneous brushing.SignificanceThese results suggest that this carbon fiber array is a uniquely robust and adaptable neural recording device, useful for specific electrophysiology measurements. In the future, this device may be useful as a bioelectric medicine tool for diagnosis and closed-loop neural control of therapeutic treatments and monitoring systems.

Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Sharpened and mechanically durable carbon fiber electrode arrays for neural interfacing

Welle

Woods

et al. 2021

Preprint

“…Due to their small diameter, carbon electrodes are more likely to land closer to regions of high electric field potential. This may lower stimulation thresholds below those used by other larger intraneural interfaces [49]. Promising preliminary stimulation results in other studies [36] enhance the prospect for this array in clinical peripheral nerve applications.…”

Section: Discussionmentioning

confidence: 96%

Sharpened and Mechanically Durable Carbon Fiber Electrode Arrays for Neural Recording

Welle

Woods

IEEE Trans. Neural Syst. Rehabil. Eng.

et al. 2021

Bioelectric medicine treatments target disorders of the nervous system unresponsive to pharmacological methods. While current stimulation paradigms effectively treat many disorders, the underlying mechanisms are relatively unknown, and current neuroscience recording electrodes are often limited in their specificity to gross averages across many neurons or axons. Here, we develop a novel, durable carbon fiber electrode array adaptable to many neural structures for precise neural recording. Carbon fibers (6.8 µm diameter) were sharpened using a reproducible blowtorch method that uses the reflection of fibers against the surface of a water bath. The arrays were developed by partially embedding carbon fibers in medical-grade silicone to improve durability. We recorded acute spontaneous electrophysiology from the rat cervical vagus nerve (CVN), feline dorsal root ganglia (DRG), and rat brain. Blowtorching resulted in fibers of 72.3 ± 33.5-degree tip angle with 146.8 ± 17.7 µm exposed carbon. Observable neural clusters were recorded using sharpened carbon fiber electrodes from rat CVN (41.8 µVpp), feline DRG (101.1 µVpp), and rat brain (80.7 µVpp). Recordings from the feline DRG included physiologically relevant signals from increased bladder pressure and cutaneous brushing. These results suggest that this carbon fiber array is a uniquely durable and adaptable neural recording device. In the future, this device may be useful as a bioelectric medicine tool for diagnosis and closedloop neural control of therapeutic treatments and monitoring systems.

“…As a summary, reducing the electrode-to-axon distance in both acute and chronic implantation increases the intrafascicular recording/stimulation quality [58] . Our approach succeeded in achieving thinner tissue encapsulation compared with previous research.…”

Section: Micro-ct Characterization Of Nerves With Untethered Minamentioning

confidence: 97%

“…During all the trials, microneedle electrodes fracture was observed caused by pressing them onto the rigid nerve holder instead of the nerve tissue, which was an alignment error. For single and multi-unit recording in peripheral nerves, microelectrode sites need to be in close proximity of an axon node due to the small extracellular fields [40] . Electrodes not penetrating the perineurium layer could be another cause of failing to record the small amplitude spike signals.…”

Section: Acute Neural Recordings Responding To Cutaneous Brushing Stimulationmentioning

confidence: 99%

Ultra-flexible and Stretchable Intrafascicular Peripheral Nerve Recording Device with Axon-dimension, Cuff-less Microneedle Electrode Array

Yan

Bottorff

et al. 2022

Preprint

Peripheral nerve mapping tools with higher spatial resolution are needed to advance systems neuroscience, and potentially provide a closed-loop biomarker in neuromodulation applications. Two critical challenges of microscale neural interfaces are (i) how to apply them to small peripheral nerves, and (ii) how to minimize chronic reactivity. We developed a flexible microneedle nerve array (MINA), which is the first high-density penetrating electrode array made with axon-sized silicon microneedles embedded in low-modulus thin silicone. We present the design, fabrication, acute recording, and chronic reactivity to an implanted MINA. Distinctive units were identified in the rat peroneal nerve. We also demonstrate a long-term, cuff-free, and suture-free fixation manner using rose bengal as a light-activated adhesive for two timepoints. The tissue response at 1-week included a sham (N=5) and MINA-implanted (N=5) group, and the response at 6-week also included a sham (N=3) and MINA-implanted (N=4) group. These conditions were quantified in the left vagus nerve of rats using histomorphometry. Micro-CT was added to visualize and quantify tissue encapsulation around the implant. MINA demonstrated a reduction in encapsulation thickness over previously quantified interfascicular methods. Future challenges include techniques for precise insertion of the microneedle electrodes and demonstrating long-term recording.