Performance of soft, brain-like neural implants in rodents in chronic experiments
Year: 2016
Type: article
Abstract: Event Abstract Back to Event Performance of soft, brain-like neural implants in rodents in chronic experiments Arati Sridharan1 and Jit Muthuswamy1 1 Arizona State University, School of Biological & Health Systems Engineering, United States Introduction: Soft interfaces are expected to improve the functionality and reliability of neural implants by mitigating the immune reactions that develop at the interface due the mechanical mismatch between the implant material and brain tissue. However, current soft materials are still several orders of magnitude stiffer than the brain tissue. In this study, we report a novel brain-like, soft material developed in our lab whose elastic modulus is comparable to brain tissue. We evaluate the chronic functionality of implants coated with the above soft, brain-like material in rodent brains. Materials and Methods: A proprietary blend of conductive silicone with carbon nanotubes was fabricated with specifications to match the elastic modulus (~5-8 kPa) and viscoelastic properties of cortical brain tissue. FTIR-ATR spectrum was acquired for the soft material using a Bruker IFS 66V/S IR spectrometer with a wide-band MCT detector cooled by liquid nitrogen under vacuum. In this study, platinum-iridium based electrode arrays (4x4 format) with 500 micron inter-electrode spacing (Microprobes, Gaithersburg, Md) were purchased and dip-coated with the soft, brain-like material. The arrays had an approximate footprint of 3 mm by 3 mm. The arrays were coated using a proprietary blend of conductive silicone and implanted in n=3 animals (CD rats) in the somatosensory cortex. Single and multi-unit neural activity was captured using TDT electrophysiological equipment (Alachua, Fl) at 24 kHz sampling frequency on a weekly basis. Collected data was analyzed using a custom program in MATLAB. Electrochemical impedance spectroscopy (10 Hz -100 kHz) was used to characterize the changes at the neural interface under chronic conditions. Results and Discussion: FTIR spectra of each fabrication step in the development of the conductive composite material showed unique features of the proprietary carbon nanotube-silicone composite blend such (a) low crosslinking leading to low elastic modulus (b) decrease in exposure of hydrophobic groups (-CH3) and (c) increased exposure of silanol groups (Si-OH) due to nanotube incorporation and additional post-treatments. The above unique features resulted in a novel material with significantly improved functionality for neural implants. Spontaneous single and multi-unit activity was observed in at least 40%-60% of the soft-coated electrodes in 2 of 3 arrays for at least 1 week with signal-to-noise ratios (SNR) greater than 15 for most of the active electrodes in 2 of 3 arrays. In one array, only one electrode showed >15 SNR post one week implantation. At least 5 electrodes (from 2 different arrays) were implanted in the barrel cortex region where mechanical stimulation of the rat whiskers resulted in increased firing rates for at least 1 week post implantation. Nyquist plots of the complex impedance spectrum showed no major changes for over one year, suggesting an electrically stable interface. Using soft-coated neural implants resulted in consistent neural activity for at least a week. Long-term recordings (>28 days) are currently been assessed for reliability in signal activity. Keywords: in vivo, biomaterial, mechanical property, bioactive interface Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: New Frontier Oral Topic: Biomaterials in microdevices and microarrays Citation: Sridharan A and Muthuswamy J (2016). Performance of soft, brain-like neural implants in rodents in chronic experiments. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.00550 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. 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Authors: Sridharan Arati, Muthuswamy Jit
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $3,801
OpenAlex ID: W2316386671