In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces

Knaack, Gretchen L.; McHail, Daniel G.; Borda, German; Koo, Beomseo; Peixoto, Nathalia; Cogan, Stuart F.; Dumas, Theodore C.; Pancrazio, Joseph J.

doi:10.3389/fnins.2016.00301

Cited by 36 publications

(23 citation statements)

References 42 publications

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“… Early micro-fabricated test electrode arrays by the Boston Retinal Implant team. ( a ) The conducting traces interconnecting the contact pads on the left with the 400 μm diameter Iridium Oxide electrodes on the right were encapsulated in HD Microsystems PI-2611 polyimide only, and quickly de-laminated under accelerated soaking conditions in saline solution at 87 °C; ( b ) multi-electrode arrays which were “wrapped” or encapsulated in 0.5 μm thick PECVD a-SiC above and below the conductors (in addition to a polyimide outer coating for scratch protection) survived for over 5 months under the same conditions, which we project to be equivalent to over 10 years at 37 °C; similar bio-stability of SiC has been demonstrated elsewhere [ 28 , 29 ]. ( c ) Cyclic voltammetry curves measured from the multi-electrode array of Figure 2 b after 20 weeks of saline soaking at 87 °C demonstrated good, consistent charge storage capacity on all 15 sites.…”

Section: Figuresupporting

confidence: 66%

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

Shire¹,

Gingerich²,

Wong³

et al. 2020

Micromachines

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We present a retrospective of unique micro-fabrication problems and solutions that were encountered through over 10 years of retinal prosthesis product development, first for the Boston Retinal Implant Project initiated at the Massachusetts Institute of Technology and at Harvard Medical School’s teaching hospital, the Massachusetts Eye and Ear—and later at the startup company Bionic Eye Technologies, by some of the same personnel. These efforts culminated in the fabrication and assembly of 256+ channel visual prosthesis devices having flexible multi-electrode arrays that were successfully implanted sub-retinally in mini-pig animal models as part of our pre-clinical testing program. We report on the processing of the flexible multi-layered, planar and penetrating high-density electrode arrays, surgical tools for sub-retinal implantation, and other parts such as coil supports that facilitated the implantation of the peri-ocular device components. We begin with an overview of the implantable portion of our visual prosthesis system design, and describe in detail the micro-fabrication methods for creating the parts of our system that were assembled outside of our hermetically-sealed electronics package. We also note the unique surgical challenges that sub-retinal implantation of our micro-fabricated components presented, and how some of those issues were addressed through design, materials selection, and fabrication approaches.

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Section: Figuresupporting

confidence: 66%

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

Shire¹,

Gingerich²,

Wong³

et al. 2020

Micromachines

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“…At postnatal day (P) 14, six male and female rats were implanted under aseptic conditions following previously described methods (Knaack et al, ; Simon et al, ). Briefly, anesthesia was induced with 5% isoflurane/oxygen mixture prior to placement in a stereotaxic frame (Kopf Instruments, Tujunga, CA).…”

Section: Methodsmentioning

confidence: 99%

Hippocampal gamma rhythms during Y‐maze navigation in the juvenile rat

McHail

Dumas

2019

Hippocampus

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The neurobiology of postnatal hippocampal development in rodents is receiving increased attention as a means to address neurodevelopmental questions and to better understand the neural code(s) for spatial navigation in adulthood. We previously showed that spontaneous alternation (SA) in a Y-maze, which emerges at the end of the third postnatal week, was related to changes in fast glutamatergic synaptic transmission. In adults, oscillations in the hippocampal local field potential (LFP) (i.e., theta, 4-12 Hz; slow gamma, 25-55 Hz; and fast gamma, 65-100 Hz) have been shown to coordinate the activity of spatially tuned cell types in the hippocampus during route planning and execution. Other investigators have shown that theta activity matures during the first month of life. However, relationships between developmental alterations in gamma oscillations and cognitive function have not been investigated in juveniles, and the impact of developmental changes in excitatory synaptic transmission on network activity remains unclear. We implanted rats at postnatal day 14 to record LFPs from the synaptic layer of area CA1 during Y-maze exploration at postnatal Days 18, 19, 23, and 24. The positive allosteric modulator of AMPA receptors, CX614, or vehicle was administered prior to each test. We found that slow gamma peak frequency, but not peak power, remained constant across this age range. Fast gamma event rate increased with increasing age, while peak frequency decreased.AMPA receptor modulation impacted slow and fast gamma differently at different ages. Furthermore, gamma events showed relationships with novelty and movement speed that differed based on gamma sub-band (slow vs. fast). These results support the presence of environmentally-driven gamma oscillations in hippocampal network activity prior to the end of the third postnatal week of development. Differential refinement of slow and fast gamma occurring across the subsequent week supports involvement in the emergence of spatial navigation ability.

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“…Alternatively, amorphous silicon carbide (a-SiC) has emerged as a candidate encapsulation material for next generation brain implants (68)(69)(70)(71). Created through plasma enhanced chemical vapor deposition, a-SiC films exhibit robust long-term stability, high electronic resistivity, and resistance to corrosion (68,72,73).…”

Section: Future Opportunities For Reproducible and Scalable Fabricatimentioning

confidence: 99%

Thinking Small: Progress on Microscale Neurostimulation Technology

Pancrazio

Deku

Ghazavi

et al. 2017

Neuromodulation: Technology at the Neural Interface

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Objectives Neural stimulation is well-accepted as an effective therapy for a wide range of neurological disorders. While the scale of clinical devices is relatively large, translational and pilot clinical applications are underway for microelectrode-based systems. Microelectrodes have the advantage of stimulating a relatively small tissue volume which may improve selectivity of therapeutic stimuli. Current microelectrode technology is associated with chronic tissue response which limits utility of these devices for neural recording and stimulation. One approach for addressing the tissue response problem may be to reduce physical dimensions of the device. “Thinking small” is a trend for the electronics industry, and for implantable neural interfaces, the result may be a device that can evade the foreign body response. Materials and Methods This review paper surveys our current understanding pertaining to the relationship between implant size and tissue response and the state-of-the-art in ultra-small microelectrodes. A comprehensive literature search was performed using PubMed, Web of Science (Clarivate Analytics), and Google Scholar. Results The literature review shows recent efforts to create microelectrodes that are extremely thin appear to reduce or even eliminate the chronic tissue response. With high charge capacity coatings, ultra-microelectrodes fabricated from emerging polymers and amorphous silicon carbide appear promising for neurostimulation applications. Conclusion We envision the emergence of robust and manufacturable ultra-microelectrodes that leverage advanced materials where the small cross-sectional geometry enables compliance within tissue. Nevertheless, future testing under in vivo conditions is particularly important for assessing the stability of thin film devices under chronic stimulation.

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In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces

Cited by 36 publications

References 42 publications

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

Micro-Fabrication of Components for a High-Density Sub-Retinal Visual Prosthesis

Hippocampal gamma rhythms during Y‐maze navigation in the juvenile rat

Thinking Small: Progress on Microscale Neurostimulation Technology

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