Shattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodes

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dc.contributor.authorEhlich, Jiřícs
dc.contributor.authorVašíček, Čeněkcs
dc.contributor.authorDobeš, Jancs
dc.contributor.authorRuggiero, Amedeocs
dc.contributor.authorVejvodová, Markétacs
dc.contributor.authorGlowacki, Eric Danielcs
dc.coverage.issue40cs
dc.coverage.volume16cs
dc.date.accessioned2025-04-04T11:56:48Z
dc.date.available2025-04-04T11:56:48Z
dc.date.issued2024-10-01cs
dc.description.abstractIt is generally accepted that for safe use of neural interface electrodes, irreversible faradaic reactions should be avoided in favor of capacitive charge injection. However, in some cases, faradaic reactions can be desirable for controlling specific (electro)physiological outcomes or for biosensing purposes. This study aims to systematically map the basic faradaic reactions occurring at bioelectronic electrode interfaces. We analyze archetypical platinum-iridium (PtIr), the most commonly used electrode material in biomedical implants. By providing a detailed guide to these reactions and the factors that influence them, we offer a valuable resource for researchers seeking to suppress or exploit faradaic reactions in various electrode materials. We employed a combination of electrochemical techniques and direct quantification methods, including amperometric, potentiometric, and spectrophotometric assays, to measure O-2, H-2, pH, H2O2, Cl-2/OCl-, and soluble platinum and iridium ions. We compared phosphate-buffered saline (PBS) with an unbuffered electrolyte and complex cell culture media containing proteins. Our results reveal that the "water window" the potential range without significant water electrolysis varies depending on the electrolyte used. In the culture medium that is rich with redox-active species, a window of potentials where no faradaic process occurs essentially does not exist. Under cathodic polarizations, significant pH increases (alkalization) were observed, while anodic water splitting competes with other processes in media, preventing prevalent acidification. We quantified the oxygen reduction reaction and accumulation of H2O2 as a byproduct. PtIr efficiently deoxygenates the electrolyte under low cathodic polarizations, generating local hypoxia. Under anodic polarizations, chloride oxidation competes with oxygen evolution, producing relatively high and cytotoxic concentrations of hypochlorite (OCl-) under certain conditions. These oxidative processes occur alongside PtIr dissolution through the formation of soluble salts. Our findings indicate that the conventional understanding of the water window is an oversimplification. Important faradaic reactions, such as oxygen reduction and chloride oxidation, occur within or near the edges of the water window. Furthermore, the definition of the water window significantly depends on the electrolyte composition, with PBS yielding different results compared with culture media.en
dc.formattextcs
dc.format.extent53567-53576cs
dc.format.mimetypeapplication/pdfcs
dc.identifier.citationACS applied materials & interfaces. 2024, vol. 16, issue 40, p. 53567-53576.en
dc.identifier.doi10.1021/acsami.4c12268cs
dc.identifier.issn1944-8252cs
dc.identifier.orcid0000-0003-0478-6875cs
dc.identifier.orcid0000-0002-0280-8017cs
dc.identifier.other191212cs
dc.identifier.urihttps://hdl.handle.net/11012/250787
dc.language.isoencs
dc.publisherAMER CHEMICAL SOCcs
dc.relation.ispartofACS applied materials & interfacescs
dc.relation.urihttps://pubs.acs.org/doi/10.1021/acsami.4c12268cs
dc.rightsCreative Commons Attribution 4.0 Internationalcs
dc.rights.accessopenAccesscs
dc.rights.sherpahttp://www.sherpa.ac.uk/romeo/issn/1944-8252/cs
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/cs
dc.subjectelectrochemistryen
dc.subjectneurostimulationen
dc.subjectplatinumelectrodesen
dc.subjectbioelectronicsen
dc.subjectreactive oxygen speciesen
dc.subjectreactive chlorine speciesen
dc.subjectwater windowen
dc.titleShattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodesen
dc.type.driverarticleen
dc.type.statusPeer-revieweden
dc.type.versionpublishedVersionen
sync.item.dbidVAV-191212en
sync.item.dbtypeVAVen
sync.item.insts2025.04.04 13:56:48en
sync.item.modts2025.04.02 14:32:11en
thesis.grantorVysoké učení technické v Brně. Středoevropský technologický institut VUT. Bioelektronické materiály a systémycs
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