Functionality and Performance of the Subretinal Implant Chip Alpha AMS

Daschner, Renate; Rothermel, Albrecht; Rudorf, Ralf; Rudorf, Sandra; Stett, Alfred

doi:10.18494/sam.2018.1726

Cited by 47 publications

(40 citation statements)

References 15 publications

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“…For in vitro electrophysiology, this material provides good results, and MEAs with TiN electrodes can be reused several times. In vivo TiN electrodes have been used as stimulation electrodes of the subretinal implant Alpha IMS with time to failure of 14.6 months (Daschner et al, 2018). We suggest that for in vivo application, for long-term cell cultures application or for combined optical stimulation and electrical recordings (Kozai and Vazquez, 2015), additional protective layers made of ALD oxides may be used.…”

Section: Discussionmentioning

confidence: 99%

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

et al. 2020

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The performance of electrode arrays insulated by low-temperature atomic layer deposited (ALD) titanium dioxide (TiO 2) or hafnium dioxide (HfO 2) for culture of electrogenic cells and for recording of extracellular action potentials is investigated. If successful, such insulation may be considered to increase the stability of future neural implants. Here, insulation of titanium nitride electrodes of microelectrode arrays (MEAs) was performed using ALD of nanometer-sized TiO 2 or hafnium oxide at low temperatures (100-200 • C). The electrode properties, impedance, and leakage current were measured and compared. Although electrode insulation using ALD oxides increased the electrode impedance, it did not prevent stable, physiological recordings of electrical activity from electrogenic cells (cardiomyocytes and neurons). The insulation quality, estimated from leakage current measurements, was less than 100 nA/cm 2 in a range of 3 V. Cardiomyocytes were successfully cultured and recorded after 5 days on the insulated MEAs with signal shapes similar to the recordings obtained using uncoated electrodes. Light-induced electrical activity of retinal ganglion cells was recorded using a complementary metal-oxide semiconductor-based MEA insulated with HfO 2 without driving the recording electrode into saturation. The presented results demonstrate that low-temperature ALD-deposited TiO 2 and hafnium oxide are biocompatible and biostable and enable physiological recordings. Our results indicate that nanometer-sized ALD insulation can be used to protect electrodes for long-term biological applications.

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Section: Discussionmentioning

confidence: 99%

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

et al. 2020

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“…horizontal, bipolar and amacrine cells) with potential to maximize natural retinal visual processing. In addition, the photodiodes allow for the detection of light as well as charge transfer to the retina, obviating the need for external devices for light detection (Daschner et al 2018). The epiretinal devices, Argus II and IRIS II, adjoin the retinal ganglion cell layer and deliver electrical impulses to the retina following external light detection through a video camera and a processing unit.…”

Section: Introductionmentioning

confidence: 99%

Highest reported visual acuity after electronic retinal implantation

Cehajic-Kapetanovic

Troelenberg²,

Edwards

et al. 2020

Acta Ophthalmologica

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To report the highest attained visual acuity with an electronic retinal implant for the treatment of advanced retinal degeneration following a novel intensive period of visual training. Methods: A case study as part of the prospective, international, multi-centre, interventional clinical trial (ClinicalTrials.gov NCT02720640 and NCT01024803) of patients with the Retina Implant Alpha AMS (Retina Implant AG, Reutlingen, Germany) for advanced retinal degeneration. A patient with subretinal device implanted into worse-seeing eye with no useful perception of light vision secondary to USH2A retinal degeneration underwent intensive period of visual training. Results: The device remains functional with no safety concerns at 3 years postsurgical implantation, and following visual training, the patient achieved the highest visual acuity so far with an electronic retinal device, with real, digitally unenhanced, reading vision of 0.04 decimal (equivalent to 1.39 LogMAR and 20/500 or 6/150 Snellen). In addition, perception as well as partial identification of obstacles and evaluation of distances was possible in both daylight and nighttime settings. Conclusions: Retinal implants are currently the only available therapy option for advanced retinal degeneration. Visual rehabilitation postimplantation has potential to maximize visual percepts. The novel concept of intensive visual training presented herein shows what is achievable with electronic retinal implants and has implications for other therapeutic options, such as optogenetics, that aim to stimulate remaining inner retinal cells in advanced retinal degeneration.

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“…The CIC is related to the material capacitance and is affected by the impedance spectrum over a frequency range corresponding to the applied stimulus waveform [11,19]. Very often, however, the impedance is reported only at one specific frequency, 1 kHz, for example [20], or even not reported at all [7,13,14,17,18]. Since highly capacitive materials are usually porous and often involve reversible electrochemical reactions, the electro-electrolyte interface is not ideally capacitive.…”

Section: Introductionmentioning

confidence: 99%

Harmonic-Balance Circuit Analysis for Electro-Neural Interfaces

Chen

Wang

Palanker

2020

Preprint

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AbstractObjectiveAvoidance of the adverse electrochemical reactions at the electrode-electrolyte interface defines the voltage safety window and limits the charge injection capacity (CIC) of an electrode material. For an electrode that is not ideally capacitive, the CIC depends on the waveform of the stimulus. We study the modeling of the charge injection dynamics to optimize the waveforms for efficient neural stimulation within the electrochemical safety limits.ApproachThe charge injection dynamics at the electrode-electrolyte interface is typically characterized by the electrochemical impedance spectrum, and is often approximated by discrete-element circuit models. We compare the modeling of the complete circuit, including a non-linear driver such as a photodiode, based on the harmonic-balance (HB) analysis with the analysis based on various discrete element approximations. To validate the modeling results, we performed experiments with iridium-oxide electrodes driven by a current source with diodes in parallel, which mimics a photovoltaic circuit.Main resultsApplication of HB analysis based on a full impedance spectrum in frequency domain eliminates the complication of finding the discrete-element circuit model in traditional approaches. HB-based results agree with the experimental data better than the discrete-element circuit analysis. HB technique can be applied not only to demonstrate the circuit response to periodic stimulation, but also to describe the initial transient behavior when a burst waveform is applied.SignificanceHB-based circuit analysis accurately describes the dynamics of electrode-electrolyte interfaces and driving circuits for all pulsing schemes. This allows optimizing the stimulus waveform to maximize the CIC, based on the impedance spectrum alone.

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Functionality and Performance of the Subretinal Implant Chip Alpha AMS

Cited by 47 publications

References 15 publications

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

Highest reported visual acuity after electronic retinal implantation

Harmonic-Balance Circuit Analysis for Electro-Neural Interfaces

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