+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Comprehensive characterization and failure modes of tungsten microwire arrays in chronic neural implants



Comprehensive characterization and failure modes of tungsten microwire arrays in chronic neural implants



Journal of Neural Engineering 9(5): 056015



For nearly 55 years, tungsten microwires have been widely used in neurophysiological experiments in animal models to chronically record neuronal activity. While tungsten microwires initially provide stable recordings, their inability to reliably record high-quality neural signals for tens of years has limited their efficacy for neuroprosthetic applications in humans. Comprehensive understanding of the mechanisms of electrode performance and failure is necessary for developing next generation neural interfaces for humans. In this study, we evaluated the abiotic (electrophysiology, impedance, electrode morphology) and biotic (microglial reactivity, blood-brain barrier disruption, biochemical markers of axonal injury) effects of 16-channel, 50 µm diameter, polyimide insulated tungsten microwires array for implant durations that ranged from acute to up to 9 months in 25 rats. Daily electrode impedance spectroscopy, electrophysiological recordings, blood and cerebrospinal fluid (CSF) withdrawals, and histopathological analysis were performed to study the time-varying effects of chronic electrode implantation. Structural changes at the electrode recording site were observed as early as within 2-3 h of electrode insertion. Abiotic analysis indicated the first 2-3 weeks following surgery was the most dynamic period in the chronic electrode lifetime as there were greater variations in the electrode impedance, functional electrode performance, and the structural changes occurring at the electrode recording tips. Electrode recording site deterioration continued for the long-term chronic animals as insulation damage occurred and recording surface became more recessed over time. In general, electrode impedance and functional performance had smaller daily variations combined with reduced electrode recording site changes during the chronic phase. Histopathological studies were focused largely on characterizing microglial cell responses to electrode implantation. We found that activated microglia were present near the electrode tracks in all non-acute animals studied, thus indicating presence of a neuroinflammatory response regardless of post-implantation survival times and electrode performance. Conversely, dystrophic microglia detectable as fragmented cells were found almost exclusively in acute animals surviving only few hours after implantation. While there was no consistent relationship between microglial cell responses and electrode performance, we noticed co-occurrence of high ferritin expression, intraparenchymal bleeding, and microglial degeneration suggesting presence of excessive oxidative stress via Fenton chemistry. Biochemical analysis indicated that these electrodes always caused a persistent release of axonal injury biomarkers even several months after implantation suggesting persistent tissue damage. Our study suggests that mechanisms of electrode failure are multi-factorial involving both abiotic and biotic parameters. Since these failure modes occur concurrently and cannot be isolated from one another, the lack of consistent relationship between electrode performance and microglial responses in our results suggest that one or more of the abiotic factors were equally responsible for degradation in electrode performance over long periods of time.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 052270180

Download citation: RISBibTeXText

PMID: 23010756

DOI: 10.1088/1741-2560/9/5/056015


Related references

Electrode impedance analysis of chronic tungsten microwire neural implants: understanding abiotic vs. biotic contributions. Frontiers in Neuroengineering 7: 13, 2014

Comprehensive characterization of tungsten microwires in chronic neurocortical implants. Conference Proceedings 2012: 755-758, 2012

Long-term stability of neural signals from microwire arrays implanted in common marmoset motor cortex and striatum. Biomedical Physics and Engineering Express 4(5):, 2018

Abiotic-biotic characterization of Pt/Ir microelectrode arrays in chronic implants. Frontiers in Neuroengineering 7: 2, 2014

Modes of failure of Osteonics constrained tripolar implants: a retrospective analysis of forty-three failed implants. Journal of Bone and Joint Surgery. American Volume 90(7): 1553-1560, 2008

Ultrasoft microwire neural electrodes improve chronic tissue integration. Acta Biomaterialia 53: 46-58, 2017

A floating microwire technique for multichannel chronic neural recording and stimulation in the awake freely moving rat. Journal Of Neuroscience Methods. 76(2): 123-133, 1997

Quantitative characterization of polyethylene debris isolated from periprosthetic tissue in early failure knee implants and early and late failure Charnley hip implants. Journal of Biomedical Materials Research 58(4): 415-420, 2001

Fabrication of silicon microwire arrays for. Applied Physics A: Materials Science & Processing 102(1): 109-114, 2011

Photoelectrochemical hydrogen evolution using Si microwire arrays. Journal of the American Chemical Society 133(5): 1216-1219, 2011

Covalent Attachment of Ferrocene to Silicon Microwire Arrays. Acs Applied Materials and Interfaces 7(48): 26959-26967, 2015

A simple method for fabricating horizontal and vertical microwire arrays. Journal of Neuroscience Methods 131(1-2): 107-110, 2003

A scanning ESR microscope using microwire arrays on a quartz sample holder. Journal of Magnetic Resonance 88(1): 130-134, 1969

The failure rate of single tooth implants replacing failed implants may be greater than the failure rate of implants placed in sites previously not treated with implants. Journal of Evidence-Based Dental Practice 9(1): 32-33, 2009

Robust deep brain stimulation functional MRI procedures in rats and mice using an MR-compatible tungsten microwire electrode. Magnetic Resonance in Medicine 73(3): 1246-1251, 2015