ORALS

SESSION: OxidativeMonPM2-R1	Yoshikawa International Symposium (2nd Intl. Symp. on Oxidative Stress for Sustainable Development of Human Beings)
Mon. 28 Nov. 2022 / Room: Ballroom B
Session Chairs: Alexander Oleinick; Christian Andre Amatore; Session Monitor: TBA

15:55: [OxidativeMonPM209] OS Plenary
Understanding Oxidative Stress in Brain with Ultramicroelectrodes: Implications for a Possible Mechanism of Alzheimer Disease
Christian Andre Amatore¹ ; ¹CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 444 [Abstract]

Oxidative stress is an essential metabolic outcome in aerobic organisms due to the activity of mitochondria in providing the basic energy of cells or during the operation of several enzymatic pools. It also serves to regulate the size and shape of organs or restructure them during foetal development by apoptosis. Oxidative stress is also indispensable to the immune system by allowing macrophages to eliminate virus, bacteria and impaired or dead cells through phagocytosis [1]. In fact, no aerobic organism could live without oxidative stress, a fact that explains why evolution maintained such unsafe mechanisms in aerobic organisms. Though, they are associated to highly negative issues. Indeed, oxidative stress mechanisms provide a variety of life-harmful radicals and species called generically Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) whose fluxes need to be finely controlled to avoid the destruction of most organic molecules (e.g., lipids in cell membranes, enzymes, etc.) and biological ones (DNA, proteins, etc.) in cells. Thus, under normal conditions, a panoply of antioxidants and enzymatic systems ensures a fine homeostatic balance. However, rupture of this delicate balance is frequent and may provoke severe damages leading to human pathologies (aging, cancers, AIDS, hearth and brain strokes, Parkinson and Alzheimer’ diseases, etc.). Using platinized carbon fiber ultramicroelectrodes we could establish that the composition of the primary oxidative stress in macrophages [1,2] and characterize the nature of functional hyperemia in the brain.3 This led us to formulate an alternative hypothesis about the onset of Alzheimer disease when Amyloid-β and ascorbate molecules are present [4,5].

References:
References
1. K. Hu, Y. Li, S.A. Rotenberg, C. Amatore, M.V. Mirkin. J. Am. Chem. Soc., 141, 2019, 4564-4568.
2. C Amatore, S. Arbault, M. Guille, F. Lemaître. Chem. Rev., 108, 2008, 2585–2621.
3. C. Amatore, S. Arbault, C. Bouton, K. Coffi, J.-C. Drapier, H. Ghandour, Y. Tong. ChemBioChem, 7, 2006, 653-661.
4. R. Giacovazzi, I. Ciofini, L. Rao, C. Adamo, C. Amatore, Phys. Chem. Phys. Chem. (PCCP), 16, 2014, 10169-10174.
5. L. Lai, C. Zhao, M. Su, X. Li, X. Liu, H. Jiang, C. Amatore, X.M. Wang. Biomater. Sc., 4, 2016, 1085-1091.

SESSION: OxidativeMonPM2-R1	Yoshikawa International Symposium (2nd Intl. Symp. on Oxidative Stress for Sustainable Development of Human Beings)
Mon. 28 Nov. 2022 / Room: Ballroom B
Session Chairs: Alexander Oleinick; Christian Andre Amatore; Session Monitor: TBA

16:20: [OxidativeMonPM210] OS
Nanometer-sized electrochemical probes for intracellular measuring ROS/RNS in single cells and cellular organelles
Christian Andre Amatore¹ ; Keke Hu² ; Alexander Oleinick³ ; Irina Svir⁴ ; Wei-hua Huang⁵ ; Yan-ling Liu⁵ ; ¹CNRS & PSL, French Academy of Sciences, Paris, France; ²Goteborg University, Gothenburg, Sweden; ³CNRS, Paris, France; ⁴Ecole Normale Superieure, Department Chemistry, PARIS, France; ⁵Wuhan University, Wuhan, China;
Paper Id: 445 [Abstract]

Oxidative stress conditions are encountered by all aerobic organisms during their whole life. Indeed, aerobic cells mostly derive their energy from the intracellular enzyme-catalyzed oxidation of fat and sugars to CO2. Also, metalloenzymes which are central actors of the respiratory chain in mitochondria are generally good reducing agents, prone to open side routes leading to O2 reduction to superoxide ion (O2•-) that is the precursor of a series of hazardous species collectively named as “reactive oxygen species (ROS)” and “reactive nitrogen species (RNS)” [1,2]. ROS and RNS may induce molecular damages to almost all organic compounds performing biological functions (nucleic acids, proteins, cells carbohydrates and lipids, etc.) – a situation termed “oxidative stress” when it runs out of control. Even without exposure to radiation or other photo-biological effects, oxidative stress can bring about such pathological conditions as inflammation, carcinogenesis, Parkinson and Alzheimer diseases, and various autoimmune illnesses, as well as accelerated ageing. The primary ROS/RNS, viz., hydrogen peroxide, peroxynitrite ion, nitric oxide, and nitrite ion, can be oxidized at different electrode potentials and therefore detected and quantified by electroanalytical techniques [3]. Nanometer-sized electrochemical probes with cylindrical shapes do not experience this problem since they can penetrate across the cell membranes that reseal around their shaft (7). They are then especially suitable for measuring ROS/RNS in single cells and cellular organelles. In this paper, we will survey recent advances in localized measurements of ROS/RNS inside single cells. Application of this method will be presented for detection of ROS/RNS in phagolysosomes during phagocytosis by macrophages (4,5). We will also evidence using these methods that remediation of Oxidative Stress in neurons artificially placed under Parkinson Disease conditions avoids the impeachment of synaptic communication when the neurons are pre-treated with Harpagide, a natural sugar derivative which alleviate the oxide stress borne by mitochondria (9).

References:
References:
(1) B. Halliwell, J.M.C. Gutteridge, Free Radicals in Biology and Medicine, 3rd ed., Oxford University Press, Oxford, 1999.
(2) F. Murad: Discovery of Some of the Biological Effects of Nitric Oxide and its Role in Cell Signaling. Nobel Lecture for Medicine, 1998, https://www.nobelprize.org/uploads/2018/06/murad-lecture.pdf
(3) C Amatore, S. Arbault, M. Guille, F. Lemaître: Electrochemical monitoring of single cell secretion: vesicular exocytosis and oxidative stress. Chem. Rev. 108 (2008) 2585–2621.
(4) K. Hu, Y.L. Liu, A. Oleinick, M.V. Mirkin, W.H. Huang, C. Amatore: Nanoelectrodes for Intracellular Measurements of Reactive Oxygen and Nitrogen Species in Single Living Cells. Curr. Opin. Electrochem., 22, 2020, 44-50, and refs therein.
(5) Y.T. Qi, H. Jiang, W.T. Wu, F.L. Zhang, S.Y. Tian, W.T. Fan, Y.L. Liu, C. Amatore, W.H. Huang: Homeostasis Inside Single Activated Phagolysosomes: Quantitative and Selective Measurements of sub-Millisecond Dynamics of ROS/RNS Production with a Nanoelectrochemical Sensor. J. Am. Chem. Soc., 144, 2022, 9723-9733.

SESSION: OxidativeMonPM2-R1	Yoshikawa International Symposium (2nd Intl. Symp. on Oxidative Stress for Sustainable Development of Human Beings)
Mon. 28 Nov. 2022 / Room: Ballroom B
Session Chairs: Alexander Oleinick; Christian Andre Amatore; Session Monitor: TBA

16:45: [OxidativeMonPM211] OS
Modelling detection of key biomolecules with enzymatic electrodes: Diffusion towards randomly distributed active sites
Giovanni Pireddu¹ ; Irina Svir² ; Alexander Oleinick³ ; Christian Andre Amatore⁴ ; ¹CNRS, Ecole Normale Superieure, Sorbonne University, Paris, France; ²Ecole Normale Superieure, Department Chemistry, PARIS, France; ³CNRS, Paris, France; ⁴CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 446 [Abstract]

Monitoring of key biomolecules and/or oxidative stress at cellular or sub-cellular levels by means of electrochemistry requires electrodes with good selectivity and sensitivity. These both characteristics often achieved by employing enzymatic electrodes. At these electrodes the enzymes are generally dispersed within a polymer layer covering electrode surface, where product(s) of the enzymatic conversion are detected. Rationalization of the experimental data imply understanding mass transport towards an enzymatic electrode which is a complicated process due to random distribution of the enzymes along the electrode surface. This process can be considered through the framework of random arrays, that is a set of active sites distributed randomly, which is also useful for description of many practical micro- and nanoscale systems [1]. As shown previously these systems can be efficiently addressed theoretically by using Voronoi diagrams [1, 2] which allows facile tessellation of the system into the unit cells around each active sites. The overall current flowing in the system can then be evaluated by modelling diffusion-reaction processes inside every unit cell and summing the contributions from individual active sites. Although this approach is tempting by its simplicity and efficiency [1] one should bear in mind that Voronoi diagram representing the unit cells by polygonal prisms remains approximation and as each approximation remains valid only under certain conditions. We have shown [3] that even for the case of diffusion limited electron transfer (ET) the actual shapes of the unit cells are more complicated and depend on the local configuration of the neighbouring active sites. This was exemplified on the small patches of the random arrays with band-like and disk-like active sites via simulations and analytical derivations. Importantly, by comparing the total and individual electrode currents obtained by employing Voronoi tessellation and simulation of the system without any approximations we found that the former are reproduced with a good accuracy while the latter are evaluated with a much larger relative error [3], thus demonstrating the limits of Voronoi tessellation for representation of such systems. Moreover, diffusion interaction between the neighbouring sites compensate the differences in unit cell sizes leading to a more uniform unit cell sizes then predicted by Voronoi tessellation [4]. This, in particular explains why the early theory of random arrays using uniform representation of the system were quantitatively successful [5].

References:
[1] O. Sliusarenko, A. Oleinick, I. Svir, C. Amatore. J. Electrochem. Soc. 167, 2020, 013530.
[2] T. J. Davies and R. G. Compton. J. Electroanal. Chem. 585, 2005, 63.
[3] G. Pireddu, I. Svir, C. Amatore, A. Oleinick, ChemElectroChem 8, 2021, 2413.
[4] G. Pireddu, I. Svir, C. Amatore, A. Oleinick, Electrochim. Acta 365, 2021, 137338.
[5] C. Amatore, J.-M. Savéant, D. Tessier, J. Electroanal. Chem. 147, 1983, 39.

SESSION: OxidativeMonPM2-R1	Yoshikawa International Symposium (2nd Intl. Symp. on Oxidative Stress for Sustainable Development of Human Beings)
Mon. 28 Nov. 2022 / Room: Ballroom B
Session Chairs: Alexander Oleinick; Christian Andre Amatore; Session Monitor: TBA

17:10: [OxidativeMonPM212] OS
Modeling of quantitative nano-amperometric measurement of sub-quantal glutamate release by living neurons
Giovanni Pireddu¹ ;⁰ ; Xiaoke Yang² ; Fu-li Zhang² ; Yan-ling Liu² ; Irina Svir³ ; Alexander Oleinick⁴ ; Wei-hua Huang² ; Christian Andre Amatore⁵ ; ¹CNRS, Ecole Normale Superieure, Sorbonne University, Paris, France; ²Wuhan University, Wuhan, China; ³Ecole Normale Superieure, Department Chemistry, PARIS, France; ⁴CNRS, Paris, France; ⁵CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 447 [Abstract]

Glutamate (Glu) is a crucial fundamental excitatory neurotransmitter released through vesicular exocytosis in the central nervous system. Dysregulation of the glutamate uptake by neurons and glial cells result in increase of the glutamate extracellular concentration leading eventually to excitotoxicity associated with increased oxidative stress and neurodegeneration [1]. Hence, quantitative measurements and interpretation of intravesicular Glu and of transient exocytotic release contents directly from individual living neurons are highly desired for understanding the mechanisms (full or sub-quantal release?) of synaptic transmission and plasticity. However, this could not be achieved so far due to the lack of adequate experimental strategies relying on selective and sensitive Glu nanosensors. We will show that a novel electrochemical Glu nanobiosensor based on a single SiC nanowire [2] is prone to selectively measure in real-time Glu fluxes released via exocytosis by large Glu vesicles (ca. 125 nm diameter) present in single hippocampal axonal varicosities as well as their intravesicular content before exocytosis by IVIEC. Combination of these two series of measurements revealed a sub-quantal release mode in living hippocampal neurons, viz., only ca. one third to one half of intravesicular Glu molecules are released by individual vesicles during exocytotic events. Importantly, this fraction remained practically the same when hippocampal neurons were pretreated with L-Glu-precursor L-glutamine, while it significantly increased after zinc treatment, although in both cases the intravesicular contents before release were drastically affected. Finally, the simulations of the electrochemical monitoring of the glutamate release events will be presented. The obtained theoretical results support the quantitative measurements with the enzymatic electrode. In addition, simulation results will also serve to discuss the meaning and adequacy of pre-calibrations performed in bulk solutions [3] to assess the analytical properties of enzyme-based electrochemical nanosensors aimed to detect fast transient release events.

References:
[1] A.A. Kritis et al. Front. Cell. Neurosci. 9 (2015) 91.
[2] X. Yang, et al. Angew. Chem. Int. Ed. 60 (2021) 15803–15808.
[3] C.P. McMahon, et al. Analyst 131 (2006) 68–72.

SESSION: BatteryTueAM-R9	Yazami International Symposium (7th Intl. Symp. on Sustainable Secondary Battery Manufacturing & Recycling)
Tue. 29 Nov. 2022 / Room: Similan 2
Session Chairs: Serge Cosnier; Katerina Aifantis; Session Monitor: TBA

11:55: [BatteryTueAM02] OS
Diffusion at arrays of randomly distributed active sites
Giovanni Pireddu¹ ; Irina Svir² ; Alexander Oleinick³ ; Christian Andre Amatore⁴ ; ¹CNRS, Ecole Normale Superieure, Sorbonne University, Paris, France; ²Ecole Normale Superieure, Department Chemistry, PARIS, France; ³CNRS, Paris, France; ⁴CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 113 [Abstract]

Many practical systems at micro- and nanoscale can be represented as arrays of active sites distributed randomly [1]. As shown previously these systems can be efficiently addressed theoretically by using Voronoi diagrams [2, 3] which allows facile tessellation of the system into the unit cells around each active sites. The overall current flowing in the system can then be evaluated by modelling diffusion-reaction processes inside every unit cell and summing the contributions from individual active sites. Although this approach is tempting by its simplicity and efficiency [3] one should bear in mind that Voronoi diagram representing the unit cells by polygonal prisms remains approximation and as each approximation remains valid only under certain conditions. In this work [4] we show that even for the case of diffusion limited electron transfer (ET) the actual shapes of the unit cells are more complicated and depend on the local configuration of the neighbouring active sites. This was exemplified on the small patches of the random arrays with band-like and disk-like active sites via simulations and in the case of band-like active sites confirmed by analytical derivations. Importantly, by comparing the total array current obtained by employing Voronoi tessellation and simulation of the system without any approximations we found that they agree well (relative error ca. 5% or less). At the same time, the individual contributions from the active sites are reproduced with a much larger relative error [4]. The latter suggests that in the case of kinetic control or reaction mechanisms that are more complicated than simple ET the diffusion-reaction competition between the active sites may become even stronger eventually leading to significant deviations from the total current predicted on the basis of the Voronoi approximation. This is currently investigated in our team.

References:
[1] O. Sliusarenko, A. Oleinick, I. Svir, C. Amatore. J. Electrochem. Soc. 167, 2020, 013530.
[2] T. J. Davies and R. G. Compton. J. Electroanal. Chem. 585, 2005, 63.
[3] O. Sliusarenko, A. Oleinick, I. Svir, C. Amatore. ChemElectroChem 2, 2015, 1279.
[4] G. Pireddu, I. Svir, A. Oleinick, C. Amatore, in preparation.