Publication detail

Direct measurement of oxygen reduction reactions at neurostimulation electrodes

EHLICH, J. MIGLIACCIO, L. SAHALIANOV, I. NIKIĆ, M. BRODSKÝ, J. GABLECH, I. VU, X. INGEBRANDT, S. GLOWACKI, E.

Original Title

Direct measurement of oxygen reduction reactions at neurostimulation electrodes

Type

journal article in Web of Science

Language

English

Original Abstract

Objective. Electric stimulation delivered by implantable electrodes is a key component of neural engineering. While factors affecting long-term stability, safety, and biocompatibility are a topic of continuous investigation, a widely-accepted principle is that charge injection should be reversible, with no net electrochemical products forming. We want to evaluate oxygen reduction reactions (ORR) occurring at different electrode materials when using established materials and stimulation protocols. Approach. As stimulation electrodes, we have tested platinum, gold, tungsten, nichrome, iridium oxide, titanium, titanium nitride, and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). We use cyclic voltammetry and voltage-step amperometry in oxygenated versus inert conditions to establish at which potentials ORR occurs, and the magnitudes of diffusion-limited ORR currents. We also benchmark the areal capacitance of each electrode material. We use amperometric probes (Clark-type electrodes) to quantify the O-2 and H2O2 concentrations in the vicinity of the electrode surface. O-2 and H2O2 concentrations are measured while applying DC current, or various biphasic charge-balanced pulses of amplitude in the range 10-30 mu C cm(-2)/phase. To corroborate experimental measurements, we employ finite element modelling to recreate 3D gradients of O-2 and H2O2. Main results. All electrode materials support ORR and can create hypoxic conditions near the electrode surface. We find that electrode materials differ significantly in their onset potentials for ORR, and in the extent to which they produce H2O2 as a by-product. A key result is that typical charge-balanced biphasic pulse protocols do lead to irreversible ORR. Some electrodes induce severely hypoxic conditions, others additionally produce an accumulation of hydrogen peroxide into the mM range. Significance. Our findings highlight faradaic ORR as a critical consideration for neural interface devices and show that the established biphasic/charge-balanced approach does not prevent irreversible changes in O-2 concentrations. Hypoxia and H2O2 can result in different (electro)physiological consequences.

Keywords

bioelectronics; neurostimulation; faradaic reactions; hypoxia; reactive oxygen species

Authors

EHLICH, J.; MIGLIACCIO, L.; SAHALIANOV, I.; NIKIĆ, M.; BRODSKÝ, J.; GABLECH, I.; VU, X.; INGEBRANDT, S.; GLOWACKI, E.

Released

1. 6. 2022

Publisher

IOP Publishing Ltd

Location

BRISTOL

ISBN

1741-2552

Periodical

Journal of Neural Engineering

Year of study

19

Number

3

State

United Kingdom of Great Britain and Northern Ireland

Pages from

036045

Pages to

36059

Pages count

15

URL

https://iopscience.iop.org/article/10.1088/1741-2552/ac77c0

Full text in the Digital Library

http://hdl.handle.net/11012/214125

BibTex

@article{BUT179261,
  author="Jiří {Ehlich} and Ludovico {Migliaccio} and Ihor {Sahalianov} and Marta {Nikić} and Jan {Brodský} and Imrich {Gablech} and Xuan Thang {Vu} and Sven {Ingebrandt} and Eric Daniel {Glowacki}",
  title="Direct measurement of oxygen reduction reactions at neurostimulation electrodes",
  journal="Journal of Neural Engineering",
  year="2022",
  volume="19",
  number="3",
  pages="15",
  doi="10.1088/1741-2552/ac77c0",
  issn="1741-2552",
  url="https://iopscience.iop.org/article/10.1088/1741-2552/ac77c0"
}