| 1. |
- Abdullaeva, Oliya, et al.
(author)
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Faradaic Pixels for Precise Hydrogen Peroxide Delivery to Control M-Type Voltage-Gated Potassium Channels
- 2022
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In: Advanced Science. - : Wiley. - 2198-3844. ; 9:3
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Journal article (peer-reviewed)abstract
- H2O2 plays a significant role in a range of physiological processes where it performs vital tasks in redox signaling. The sensitivity of many biological pathways to H2O2 opens up a unique direction in the development of bioelectronics devices to control levels of reactive-oxygen species (ROS). Here a microfabricated ROS modulation device that relies on controlled faradaic reactions is presented. A concentric pixel arrangement of a peroxide-evolving cathode surrounded by an anode ring which decomposes the peroxide, resulting in localized peroxide delivery is reported. The conducting polymer (poly(3,4-ethylenedioxythiophene) (PEDOT), is exploited as the cathode. PEDOT selectively catalyzes the oxygen reduction reaction resulting in the production of hydrogen peroxide (H2O2). Using electrochemical and optical assays, combined with modeling, the performance of the devices is benchmarked. The concentric pixels generate tunable gradients of peroxide and oxygen concentrations. The faradaic devices are prototyped by modulating human H2O2-sensitive Kv7.2/7.3 (M-type) channels expressed in a single-cell model (Xenopus laevis oocytes). The Kv7 ion channel family is responsible for regulating neuronal excitability in the heart, brain, and smooth muscles, making it an ideal platform for faradaic ROS stimulation. The results demonstrate the potential of PEDOT to act as an H2O2 delivery system, paving the way to ROS-based organic bioelectronics.
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| 2. |
- Matter, Lukas, 1995, et al.
(author)
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Bioelectronic Direct Current Stimulation at the Transition Between Reversible and Irreversible Charge Transfer
- 2024
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In: Advanced Science. - : John Wiley and Sons Inc. - 2198-3844.
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Journal article (peer-reviewed)abstract
- Many biological processes rely on endogenous electric fields (EFs), including tissue regeneration, cell development, wound healing, and cancer metastasis. Mimicking these biological EFs by applying external direct current stimulation (DCS) is therefore the key to many new therapeutic strategies. During DCS, the charge transfer from electrode to tissue relies on a combination of reversible and irreversible electrochemical processes, which may generate toxic or bio-altering substances, including metal ions and reactive oxygen species (ROS). Poly(3,4-ethylenedioxythiophene) (PEDOT) based electrodes are emerging as suitable candidates for DCS to improve biocompatibility compared to metals. This work addresses whether PEDOT electrodes can be tailored to favor reversible biocompatible charge transfer. To this end, different PEDOT formulations and their respective back electrodes are studied using cyclic voltammetry, chronopotentiometry, and direct measurements of H2O2 and O2. This combination of electrochemical methods sheds light on the time dynamics of reversible and irreversible charge transfer and the relationship between capacitance and ROS generation. The results presented here show that although all electrode materials investigated generate ROS, the onset of ROS can be delayed by increasing the electrode's capacitance via PEDOT coating, which has implications for future bioelectronic devices that allow longer reversibly driven pulse durations during DCS.
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| 3. |
- Miglbauer, Eva, 1992-
(author)
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Bioelectronic Approaches for On-Demand Generation of Reactive Oxygen Species
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Reactive oxygen species (ROS) are an integral part of our lives. They perform essential functions in our biology and are, due to their high oxidative power, key molecules in advanced oxidation processes in industrial applications such as treatment of wastewater. Likewise, they play a crucial role as active intermediates in chemodynamic or photodynamic therapy of cancer. ROS, such as hydrogen peroxide (H2O2) or hydroxyl radicals (OH·), are derived from molecular oxygen (O2), and represent relatively more reactive oxidants with respect to parent O2.At the cellular level, ROS are produced primarily in mitochondria and among others take part in cell signaling and maintaining redox homeostasis. However, when exceeding a certain threshold, ROS can lead to oxidative stress and consequently to cardiovascular and neurodegenerative diseases, as well as cell death. Yet, the ability of modulating the generation of ROS externally gives the possibility to treat certain diseases as well. Advanced oxidation processes such as photoinduced generation of ROS and Fenton-like processes consisting of reactions of H2O2 with transition metal ions are particularly potent and tunable approaches of ROS generation.The aim of this thesis is to expand the range of applications for advanced oxidation processes, and it includes device and electrode fabrication and characterization for local ROS generation and delivery.In paper 1, we exploited naturally-sourced lignins, which share critical structural features with known photocatalysts, to photochemically reduce O2 to H2O2 with simultaneous degradation of the biopolymer, when irradiated with UV light. By adding electron donors, the autoxidation of the lignins was reduced and H2O2 generation partially increased. By showing the possibility to destructively photooxidize lignins to produce H2O2 we contribute to new developments of valorization of lignins and engineering solutions.In paper 2, we created an electro-Fenton device which electrochemically generates H2O2 and simultaneously dissolves chromium. Chromium ions and H2O2 are cytotoxic in their own right, but also can react with each other to form highly oxidizing hydroxyl radicals. We demonstrated the ability of these electrochemically-generated species to induce cell death in a metastatic human skin cancer cell line. In paper 3 we spun the concept of paper 2 further and demonstrated biphasic electro-Fenton reaction on a single stainless steel electrode and showed the generation of hydroxyl radicals with autoluminescense measurements in situ. In paper 4, we investigated the anodic contributions of electrodes in physiological conditions in regards of ROS formation to shed light onto possible electrochemically induced processes contributing to the disintegration of cells by current treatment. Studying the application of oxygen reduction reaction, electro-fenton processes, and oxidation processes in physiological environment leads to a better understanding of electrochemical processes and could further simplified, cheap and locally applied direct current tissue ablation in anti-tumor treatment with decreased systemic side effects.In summary this thesis elaborates various novel methods of on-demand ROS generation. Paper 1 is a photoinduced process, while papers 2-4 introduce various methods of electrochemical ROS generation via combinations of cathodic (oxygen reduction reactions) and anodic (metal corrosion, direct water oxidation) processes.
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| 4. |
- Miglbauer, Eva, 1992-, et al.
(author)
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Faradaic Fenton Pixel – Reactive Oxygen Species Delivery using Au/Cr Electrochemistry
- 2023
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In: ChemBioChem. - : John Wiley & Sons. - 1439-4227 .- 1439-7633. ; 24:17
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Journal article (peer-reviewed)abstract
- Reactive oxygen species (ROS) are an integral part of many anticancer therapies. Fenton-like processes involving reactions of peroxides with transition metal ions are a particularly potent and tunable subset of ROS approaches. Precise on-demand dosing of the Fenton reaction is an area of great interest. Herein, we present a concept of an electrochemical faradaic pixel which produces controlled amounts of ROS via a Fenton-like process. The pixel comprises a cathode and anode, where the cathode reduces dissolved oxygen to hydrogen peroxide. The anode is made of chromium, which is electrochemically corroded to yield chromium ions. Peroxide and chromium interact to form a highly oxidizing mixture of hydroxyl radicals and hexavalent Cr-ions. After benchmarking the electrochemical properties of this type of device, we demonstrate how it can be used under in vitro conditions with a cancer cell line. The faradaic Fenton pixel is a general and scalable concept that can be used for on-demand delivery of redox-active products for controlling a physiological outcome.
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| 5. |
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| 6. |
- Sahalianov, Ihor, et al.
(author)
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Volumetric Double-Layer Charge Storage in Composites Based on Conducting Polymer PEDOT and Cellulose
- 2021
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In: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 4:8, s. 8629-8640
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Journal article (peer-reviewed)abstract
- Energy storage technology incorporating conducting polymers as the active component in electrode structures, in part based on natural materials, is a promising strategy toward a sustainable future. Electronic and ionic charge transport in poly(3,4-ethylenedioxythiophene) (PEDOT) provides fundamentals for energy storage, governed by volumetric PEDOT:counterion double layers. Despite extensive experimental investigations, a solid understanding of the capacitance in PEDOT-based nanocomposites remains unsatisfactory. Here, we report on the charge storage mechanism in PEDOT composited with cellulose nanofibrils (termed as "power paper") from three different perspectives: experimental measurements, density functional theory atomistic simulations, and device-scale simulations based on the NernstPlanck-Poisson equations. The capacitance of the power paper was investigated by varying the film thickness, charging currents, and electrolyte ion concentrations. We show that the volumetric capacitance of the power paper originates from electrostatic molecular double layers defined at atomistic scales, formed between holes, localized in the PEDOT backbone, and their counterions. Experimental galvanostatic cycling characteristics of the power paper is well reproduced within the electrostatic Nernst-PlanckPoisson model. The difference between the specific capacitance and the intrinsic volumetric capacitance is also outlined. Substantial oxygen reduction reactions were identified and recorded in situ in the vicinity of the power paper surface at negative potentials. Purging of dissolved oxygen from the electrolyte leads to the elimination of currents originating from the oxygen reduction reactions and allows us to obtain well-defined electrostatic-capacitive behavior (box-shaped cyclic voltammetry and triangular galvanostatic charge-discharge characteristics) at a large operational potential window from -0.6 V to +0.6 V. The obtained results reveal that the fundamental charge storage is a result of electrostatic Stern double layers in both oxidized and reduced electrodes, and the developed theoretical approaches provide a predictive tool to optimize performance and device design for energy storage devices based on highperformance conducting polymer electrodes.
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