H2O2 Formation Research Articles

Impact of heat-not-burn cigarette passive smoking on children's oxidative stress, endothelial and platelet function

Growing global use of heat-not-burn cigarettes (HNBC) prompts investigation. Prior studies assessed HNBC's effects on cardiovascular health, revealing heightened oxidative stress, platelet activation, and endothelial dysfunction. However, limited understanding exists regarding passive smoking's impact on children exposed to HNBC.This study aims to assess levels of oxidative stress, endothelial and platelet function among children exposed to passive smoke from HNBC, traditional tobacco (TT) cigarettes and unexposed subjects.Seventy-eight children (2–18 years) were divided into three groups: HNBC passive smokers (n = 26), TT cigarette exposed (n = 26), and control (CNT) group (n = 26, unexposed).Oxidative stress was evaluated by serum NADPH oxidase-2 (NOX2) activity, assessed by soluble Nox2-derived peptide (sNOX2-dp), isoprostanes, hydrogen peroxide (H2O2) production, hydrogen break-down activity (HBA) and NO bioavailability. Endothelial function was assessed by brachial flow-mediated dilation (FMD). Platelet function was evaluated by soluble CD40 ligand (sCD40L), soluble P-selectin (sP-selectin) and thrombus formation by T-TAS analysis.Passive smoking-exposed children (both HNBC and TT) exhibited significantly increased serum sNOX2-dp, isoprostanes, H2O2, sCD40L sP-selectin and thrombus formation versus controls. Conversely, exposed children displayed reduced brachial FMD and serum NO bioavailability. No significant differences were found between children exposed to passive smoking of HNBC vs TT.Multivariable regression linked sNOX2 (standardized coefficient β: 0.284; SE: 0.040; p = 0.01) and H2O2 (standardized coefficient β: 0.243; SE: 0.0; p = 0.02) as independent predictors of FMD, and isoprostanes (standardized coefficient β:0.388; SE: 0.022; p < 0.001) and serum cotinine (standardized coefficient β:0.270; SE: 0.048; p = 0.01) with sNOX2-dp levels.Exposure to HNBC smoke heightened oxidative stress, endothelial dysfunction, platelet activation, and thrombus formation in children. Findings suggest avenues for interventions to curb childhood passive smoking exposure.

Indirect H2O2 synthesis without H2

Industrial hydrogen peroxide (H2O2) is synthesized using carbon-intensive H2 gas production and purification, anthraquinone hydrogenation, and anthrahydroquinone oxidation. Electrochemical hydrogenation (ECH) of anthraquinones offers a carbon-neutral alternative for generating H2O2 using renewable electricity and water instead of H2 gas. However, the H2O2 formation rates associated with ECH are too low for commercialization. We report here that a membrane reactor enabled us to electrochemically hydrogenate anthraquinone (0.25 molar) with a current efficiency of 70% at current densities of 100 milliamperes per square centimeter. We also demonstrate continuous H2O2 synthesis from the hydrogenated anthraquinones over the course of 48 h. This study presents a fast rate of electrochemically-driven anthraquinone hydrogenation (1.32 ± 0.14 millimoles per hour normalized per centimeter squared of geometric surface of electrode), and provides a pathway toward carbon-neutral H2O2 synthesis.

Improving dispersion of indium polyphthalocyanine on carbon nanotube via molecular modification for efficient oxygen reduction to hydrogen peroxide

Molecular catalysts have emerged as the promising candidate for oxygen reduction to hydrogen peroxide (H2O2). Dispersing homogeneously molecular catalyst on carbon support is the prerequisite for actual electrocatalysis application. Herein, we proposed a novel strategy of modification with sodium dodecylbenzenesulfonate (SDBS) to improve dispersion of indium polyphthalocyanine (InPPc) on carbon nanotube (CNT). The SDBS modification induces the matched surface hydrophilicity of CNT with InPPc, preventing InPPc aggregation. As a result, the InPPc/SDBS@CNT exhibits a remarkable onset potential of 0.84 V vs. RHE and selectivity of > 95 %, superior to InPPc/CNT and most recently reported catalysts. In situ Raman spectrum identifies the critical *OOH intermediate during H2O2 formation on InPPc/SDBS@CNT. Importantly, the InPPc/SDBS@CNT presents a prominent H2O2 production rate of 24.88 mg/cm2/h over 12 h in flow cell. This work provides an effective strategy to promote practical application of molecular catalysts.

Enhancing Cu-EDTA decomplexation in a discharge plasma system coupled with nanospace confined iron oxide: Insights into electron transfer and high-valent iron species

Decomplexation of heavy metal-organic complexes dominated by reactive oxygen species (ROS) oxidation had attracted extensive attention. Nanospace confinement is a novel strategy to enhance pollutant removal due to its regulation on ROS transformation and local accelerated dynamics. Herein, nano-confined Fe2O3 catalyst supported by carbon nanotubes (Fe2O3-in-CNTs) was synthesized, and it displayed obvious synergistic effects on decomplexation of Cu-EDTA complex in a non-thermal plasma (NTP) process. Cu-EDTA decomplexation efficiency reached 98.8% within 20 min in the NTP/Fe2O3-in-CNTs system, and the corresponding kinetic constant was 4.5 and 2.5 times as that in single NTP and unconfined systems, respectively. Based on experimental and theoretical results, nanospace confinement induced electron localization around Fe and C atoms and rearrangement of orbital electrons, favoring strongly oxidative FeⅣ formation and catalytic decomposition of H2O2 and O3. Nanospace confinement made Cu-EDTA decomplexation process transform from radical pathway to non-radical pathway. Cu-EDTA decomplexation pathways in the NTP/Fe2O3-in-CNTs were proposed.

Hf and Co Dual Single Atoms Co-Doped Carbon Catalyst Enhance the Oxygen Reduction Performance.

Single-atom metal-doped M-N-C (M═Fe, Co, Mn, or Ni) catalysts exhibit excellent catalytic activity toward oxygen reduction reactions (ORR). However, their performance still has a large gap considering the demand for their practical applications. This study reports a high-performance dual single-atom doped carbon catalyst (HfCo-N-C), which is prepared by pyrolyzing Co and Hf co-doped ZIF-8 . Co and Hf are atomically dispersed in the carbon framework and coordinated with N to form Co-N4 and Hf-N4 active moieties. The synergetic effect between Co-N4 and Hf-N4 significantly enhance the catalytic activity and durability of the catalyst. In an acidic medium, the ORRhalf-wave potential (E1/2) of the catalyst is up to 0.82V , which is much higher than that of the Co-N-C catalyst without Hf co-doping (0.80V). The kinetic current density of the catalyst is up to 2.49Acm-2 at 0.85V , which is 1.74 times that of the Co-N-C catalyst without Hf co-doping. Moreover, the catalyst exhibits excellent cathodic performance in single proton exchange membrane fuel cells and Zn-air batteries. Furthermore, Hf co-doping can effectively suppress the formation of H2O2, resulting in significantly improved stability and durability.

Leveraging phenazine and dihydrophenazine redox dynamics in conjugated microporous polymers for high-efficiency overall photosynthesis of hydrogen peroxide.

Harnessing solar energy for hydrogen peroxide (H2O2) production from water and oxygen is crucial for sustainable solar fuel generation. Conjugated microporous polymers (CMPs), with their vast structural versatility and extended π-conjugation, are promising photocatalysts for solar-driven H2O2 generation, though enhancing their efficiency is challenging. Inspired by the crucial role of phenazine derives in biological redox cycling and electron transfer processes, the redox-active phenazine moiety is rationally integrated into a CMP framework (TPE-PNZ). By leveraging the reversible redox dynamics between phenazine and dihydrophenazine, TPE-PNZ sets a new benchmark for H2O2 production among CMP-based photocatalysts, reaching a production rate of 5142 μmol g-1 h-1 and a solar-to-chemical conversion efficiency of 0.58% without requiring sacrificial agents. This interconversion allows for the storage of photogenerated electrons by phenazine and subsequent conversion into dihydrophenazine, which then reduces O2 to H2O2 while reverting to phenazine, markedly facilitating charge transfer and mitigating charge recombination. Experimental and computational investigations further reveal that this reversible process enhances O2 adsorption and reduction, significantly lowering the energy barrier towards H2O2 formation. This study offers critical insights into designing advanced materials for sustainable energy research.

Boosting the charge for the selective photoelectrochemical oxidation of hydroquinone in hazardous environments using a fine-tuned heterojunction catalyst

A heterojunction semiconductor PEC is used to boost the charge for HQ oxidation and H2O2 formation under visible light. The composite is successfully employed for the sensitive and selective determination of HQ in different environments.

Solvent stabilization of alkene epoxidation transition states within Ti-MFI: Interactions near and far from active sites

Kinetics of alkene epoxidation in Ti incorporated MFI (Ti-MFI) zeolites that contact liquid methanol (CH3OH) depend strongly on the bulk concentration of water ([H2O]) and the density of silanol groups ((SiOH)x) within the framework, because these species influence excess free energy contributions (Gε) that stabilize transition states for epoxidation and hydrogen peroxide derived reactive intermediates. These effects rely on hydrogen bonds among intrapore molecules that couple catalytic events to the structure of the surrounding solvent molecules. Turnover rates for 1-hexene (C6H12) epoxidation with hydrogen peroxide over Ti-MFI zeolites increase by ten-fold both when either [H2O] or (SiOH)x densities increase. Activation enthalpies and entropies of hydrophilic and hydrophobic Ti-MFI materials are similar at the lowest [H2O] (0.005 M H2O), implying solvation environments near active sites do not depend on defect density in the near-absence of H2O. However, kinetic barriers for these same Ti-MFI materials increase and diverge from one another as non-monotonic functions of [H2O] (0.005–5 M H2O), and these differences reflect stabilizing contributions from discrete solvation shells both adjacent (near) and further (or far) from active sites. The structure of these solvation shells must reorganize to accommodate H2O2 activation and formation of epoxidation transition states. Adsorption enthalpies for the epoxide product become more exothermic with larger values of [H2O] over each Ti-MFI catalyst, and the apparent activation enthalpies generally increase as epoxide adsorption enthalpies become more exothermic. Comparisons to trends previously obtained for Ti-BEA catalysts suggest the negative correlation indicates that excess contributions (Hε, Gε) impact reactive species (Ti-OOH) within the 10-membered ring pores of MFI to a greater extent than 12-membered ring pores due to distinctions among hydrogen bonding interactions among bound reactive species, spectating solvent molecules, and extended surfaces of MFI pores.

Metallic Copper-Based Dual-Enzyme Biomimetic Nanoplatform for Mild Photothermal Enhancement of Anticancer Catalytic Activity.

Background: Chemodynamic therapy (CDT) is recognized as a promising cancer treatment. Recently, copper sulfide nanostructures have been extensively employed as Fenton-like reagents that catalyze the formation of acutely toxic hydroxyl radicals (·OH) from hydrogen peroxide (H2O2). However, CDT therapeutic potency is restricted by the tumor microenvironment (TME), such as insufficient amounts of hydrogen peroxide, excessive glutathione levels, etc. To address these disadvantages, glucose oxidase (GOx) or catalase (CAT) can be utilized to enhance CDT, while low therapeutic efficacy still inhibits their future applications. Our previous study revealed that mild photothermal effect could boost the CDT catalytic effectiveness as well as GOx enzyme activity over a range. Results: We engineered and constructed a hollow CuS nanoplatform loaded with GOx and CAT, coating with macrophage membranes (M@GOx-CAT@CuS NPs). The nanoplatforms allowed enhancement of the reactive oxygen species creation rate and GOx catalytic activeness of CDT through mild phototherapy directed by photoacoustic imaging. After actively targeting vascular cell adhesion molecule-1 (VCAM-1) in cancer cells mediated by macrophage membrane coating, M@GOx-CAT@CuS NPs released GOx and CAT under near-infrared irradiation. GOx catalyzed the formation of H2O2 and gluconic acid with glucose, creating a better catalytic environment for CDT. Meanwhile, CAT-catalyzed H2O2 decomposition to generate sufficient oxygen, appropriately alleviating the oxygen shortage in the TME. In addition, starvation effects decreased adenosine triphosphate levels and further underregulated heat shock protein expression to reduce the heat resistance of tumor cells, resulting in a better mild phototherapy outcome. Both invitro and invivo experiments demonstrated that the newly developed M@GOx-CAT@CuS nanoplatform has remarkable synergistic anticancer therapeutic effects. Conclusion: The cascade reaction-enhanced biomimetic nanoplatform opens up a new avenue for precision tumor diagnostic and therapeutic research.

Recent advances in the electrochemical production of hydrogen peroxide

Hydrogen peroxide (H2O2) is an innovative and environmentally friendly oxidant that finds wide-ranging applications across multiple industries. In the past, H2O2 production predominantly relied on the anthraquinone method, which had drawbacks such as the generation of organic waste and the requirement for energy-intensive reactions. A cheap, efficient, and sustainable way of producing H2O2 may be achieved through the redox reaction between oxygen and water. On both small and large scales, the electrosynthesis of H2O2 is practical and affordable. In recent years, it has been thought that the energy-intensive anthraquinone process may be replaced by the electrochemical synthesis of H2O2 via the two-electron oxygen reduction reaction (ORR) route. To eliminate the organic pollutants found in drinking water and industrial effluent, highly effective hydrogen peroxide (H2O2) must be produced electrochemically using gas diffusion electrodes (GDEs). Compared to other carbonaceous cathodes, the GDEs as cathodic electrocatalysts demonstrate greater cost-effectiveness, lower energy consumption, and higher oxygen utilization efficiency for the formation of H2O2. A promising alternative for enabling the growth of sustainable economics in the W&W sector is microbial electrochemical systems (MESs) that create H2O2. To enhance the efficiency and predictability of H2O2 production in MESs, a machine-learning approach was adopted, incorporating a meta-learning methodology to forecast the generation rate of H2O2 in MES based on the seven input variables, comprising several design and operational parameters.

Busting the myth of spontaneous formation of H2O2 at the air-water interface: contributions of the liquid-solid interface and dissolved oxygen exposed.

Recent reports on the spontaneous formation of hydrogen peroxide (H2O2) at the air-water and solid-water interfaces challenge our current understanding of aquatic chemistry and have ramifications on atmosphere chemistry models, surface science, and green chemistry. Suggested mechanisms underlying this chemical transformation include ultrahigh instantaneous electric fields at the air-water interface and the oxidation of water and reduction of the solid at the solid-water interface. Here, we revisit this curious problem with NMR spectroscopy (with an H2O2 detection limit ≥50 nM) and pay special attention to the effects of nebulizing gas, dissolved oxygen content, and the solid-water interface on this chemical transformation in condensed and sprayed water microdroplets. Experiments reveal that the reduction of dissolved oxygen at the solid-water interface predominantly contributes to the H2O2 formation (not the oxidation of hydroxyl ions at the air-water interface or the oxidation of water at the solid-water interface). We find that the H2O2 formation is accompanied by the consumption (i.e., reduction) of dissolved oxygen and the oxidation of the solid surface, i.e., in the absence of dissolved oxygen, the formation of H2O2(aq) is not observed within the detection limit of ≥50 nM. Remarkably, the tendency of the solids investigated in this work towards forming H2O2 in water followed the same order as their positions in the classic Galvanic series. These findings bust the prevailing myths surrounding H2O2 formation due to the air-water interface, the ultrahigh electric fields therein, or the micro-scale of droplets. The hitherto unrealized role of the oxidation of the solid surface due to dissolved oxygen in the formation of H2O2 is exposed. These findings are especially relevant to corrosion science, surface science, and electrochemistry, among others.

Redox reactions of a pyrazine-bridged RuIII(edta) binuclear complex: spectrochemical, spectroelectrochemical and theoretical studies.

The redox reactions of a pyrazine-bridged binuclear [(edta)RuIIIpzRuIII(edta)]2- (edta4- = ethylenediaminetetraacetate; pz = pyrazine) have been investigated spectrochemically and spectroelectrochemically for the first time. The kinetics of the reduction of [(edta)RuIIIpzRuIII(edta)]2- (RuIII-RuIII) with the ascorbic acid anion (HA-) was studied as a function of ascorbic concentration and temperature at a fixed pH 6.0. The overall reaction of RuIII-RuIII was found to consist of two-steps involving the initial formation of the mixed-valence [(edta)RuIIpzRuIII(edta)]3- (RuII-RuIII) intermediate complex (λmax = 462 nm, εmax = 10 000 M-1 cm-1), which undergoes further reduction by ascorbic acid to produce the [(edta)RuIIpzRuII(edta)]4-(RuII-RuII) ultimate product complex (λmax = 540 nm, εmax = 20 700 M-1 cm-1). Our studies further revealed that the RuII-RuIII and RuII-RuII species are formed in the electrochemical reduction of the RuIII-RuIII complex at 0.0 and -0.4 V (vs. SHE), respectively. Formation of RuII-RuIII and RuII-RuII was further corroborated by magnetic moment measurements and DFT calculations. Kinetic data and activation parameters are interpreted in terms of a mechanism involving rate-determining outer-sphere electron transfer between Ru(III) and the ascorbate monoanion (HA-) at pH 6.0. A detailed reaction mechanism in agreement with the spectral, spectro-electrochemical and kinetic data is presented. The results of the spectral and kinetic studies of the reaction of the RuII-RuII complex with molecular oxygen (O2) reveal the ability of the RuII-RuII species to effect the oxygen reduction reaction (ORR) leading to the formation of H2O2, a partial reduction product of dioxygen (O2).

Combination of High-Dose Parenteral Ascorbate (Vitamin C) and Alpha-Lipoic Acid Failed to Enhance Tumor-Inhibitory Effect But Increased Toxicity in Preclinical Cancer Models.

Intravenous vitamin C (IVC, ascorbate [Asc]) and alpha-lipoic acid (ALA) are frequently coadministered in integrative oncology clinics, with limited understanding of combination effects or drug-drug interactions. As high-dose IVC has anticancer activity through peroxide (H2O2), it is hypothesized that IV ALA, a thiol antioxidant, might have untoward effects when combined with IVC. In vitro combination index (CI) was investigated in 6 types of human cancer cells, using clinically relevant concentrations of Asc (0.625-20 mM) and ALA (0.25, 0.5, and 1 mM) evaluated by nonconstant ratio metrics. Cellular H2O2 was measured using HeLa cells expressing a fluorescent probe HyPer. Mouse xenografts of the metastatic breast cancer MDA-MB-231 were treated with intraperitoneal injections of ALA (10, 20, and 50 mg/kg) and Asc (0.2, 0.5, and 4 g/kg) at various dose levels. Cancer cell lines were sensitive to Asc treatment but not to ALA. There is no evidence ALA becomes a prooxidant at higher doses. The CIs showed a mixture of synergistic and antagonistic effects with different ALA and Asc combination ratios, with a "U" shape response to Asc concentrations. The ALA concentrations did not influence the CIs or cellular H2O2 formation. Adding ALA to Asc dampened the increase of H2O2. Toxicity was observed in mice receiving prolonged treatment of ALA at all doses. The Asc at all doses was nontoxic. The combination of ALA and Asc increased toxicity. The ALA at all doses did not inhibit tumor growth. The Asc at 4 g/kg inhibited tumor growth. Adding ALA 50 mg/kg to Asc 4 g/kg did not enhance the effect, but lower doses of ALA (10 or 20 mg/kg) dampened the inhibitory effect of Asc. These data do not support the concurrent or relative concurrent use of high-dose intravenous ALA with prooxidative high-dose IVC in clinical oncology care with potentially increased toxicity.

Examining the Antioxidant and Superoxide Radical Scavenging Activity of Anise, (Pimpinella anisum L. Seeds), Esculetin, and 4-Methyl-Esculetin Using X-ray Diffraction, Hydrodynamic Voltammetry and DFT Methods.

Pimpinella anisum L., or anise, is a plant that, besides its nutritional value, has been used in traditional medical practices and described in many cultures in the Mediterranean region. A possible reason for anise's therapeutic value is that it contains coumarins, which are known to have many biomedical and antioxidant properties. HPLC analysis in our laboratory of the anise extract shows the presence of the coumarin esculetin. We used a hydrodynamic voltammetry rotating ring-disk electrode (RRDE) method to measure the superoxide scavenging abilities of anise seeds and esculetin, which has marked scavenging activity. A related coumarin, 4-methyl-esculetin, also showed strong antioxidant activity as measured by RRDE. Moreover, this study includes the X-ray crystal structure of esculetin and 4-methyl-esculetin, which reveal the H-bond and the stacking intermolecular interactions of the two coumarins. Coordinates of esculetin crystal structure were used to perform a DFT study to arrive at the mechanism of superoxide scavenging. Besides performing a H(hydroxyl) abstraction in esculetin position 6 by superoxide, the scavenging also includes the presence of a second superoxide radical in a π-π approach. Both rings of esculetin were explored for this attack, but only the pyrone ring was effective. As a result, one product of esculetin scavenging is H2O2 formation, while the second superoxide remains π-π trapped within the pyrone ring to form an esculetin-η-O2 complex. Comparison with other coumarins shows that subtle structural differences in the coumarin framework can imply marked differences in scavenging. For instance, when the catechol moiety of esculetin (position 6,7) is shifted to position 7,8 in 4-methyl-7,8-dihydroxy coumarin, that coumarin shows a superoxide dismutase action, which, beside H2O2 formation, includes the formation and elimination of a molecule of O2. This is in contrast with the products formed through esculetin superoxide scavenging, where a second added superoxide remains trapped, and forms an esculetin-η-O2 complex.

Nanostructured Fe-N-C Electrocatalysts with CeO2 Additives for PEM Fuel Cells

The development of cost-effective electrocatalysts for polymer electrolyte membrane fuel cells (PEM fuel cells) is essential for the widespread use of this technology. The high cost and limited availability of Pt-group metals (PGMs) used as catalyst materials are the main barriers to the widespread commercialization and development of PEM fuel cells. [1] Therefore, the use of high surface area and effective catalysts without Pt have gained great importance in PEM fuel cells. This study introduces high surface area electrocatalysts that are free of platinum group metals (non-PGM) consisting of iron-nitrogen-carbon (Fe-N-C). Here, the uniform distribution of Fe was achieved using graphene oxide (GO) nanoparticles to enhance the catalyst's performance for oxygen reduction reaction (ORR). [2] Furthermore, the addition of a small amount of cerium oxide (CeO2) nanoparticles to the catalyst layer helps to prevent the degradation of the catalyst and ionomer by preventing H2O2 formation as well as increasing the ORR activity due to high oxygen storage capacity. [3] Initially, GO is synthesized by improved Hummer’s method. The GO nanoparticles are obtained through a process involving ball-milling and acid treatment. These nanoparticles are then thermally reduced and nitrogen-doped to form nitrogen-doped reduced graphene oxide nanoparticles. Fe-N-C complexes are synthesized by reacting these nanoparticles with FeCl2 precursor, which are then hydrothermally treated to introduce CeO2 additives. The resulting catalysts are analyzed using various techniques (FT-IR, XPS, SEM, TEM, EDX) and display excellent electrochemical performance. The ORR activity of the Fe-N-C catalysts was investigated and compared with the electrocatalysts prepared with larger graphene oxide particles. A similar comparison is also made with and without CeO2 additives. The authors gratefully acknowledge the financial support of The Scientific and Technological Research Council of Turkey (TÜBİTAK) (Grant Number: 122M429) References [1] He, C., Desai, S., Brown, G., & Bolleplli, S. (2005). PEM fuel cell catalysts: Cost, performance, and durability. The electrochemical society Interface, 14(3), 41.[2] Weiss, J., Zhang, H., & Zelenay, P. (2020). Recent progress in the durability of Fe-NC oxygen reduction electrocatalysts for polymer electrolyte fuel cells. Journal of Electroanalytical Chemistry, 875, 114696.[3] Taşdemir, A., Iskandarani, B., Yürüm, A., Gürsel, S. A., & Kaplan, B. Y. (2021). CeO2 nanorod decorated NrGO additives for boosting PEMFC performance. International Journal of Hydrogen Energy, 46(63), 32250-32260.

Using Plasma-Activated Water Generated by an Air Gliding Arc as a Nitrogen Source for Rice Seed Germination

This research aimed to understand the use of air gliding arc (GA) plasma to generate plasma-activated water (PAW) for fixing nitrogen in water and the chemical properties of PAW on the germination of rice seeds. The N2, NO, and OH molecules in GA plasma led to NO3−, NO2−, and H2O2 formation in the PAW. The NO3−, NO2−, and H2O2 contents in PAW rapidly decreased after 5 days of storage. The experiment was arranged in a completely randomised design using GA plasma discharged above the surface of deionised (DI) water with different airflow rates (2, 3, 4, 5, and 6 L/min) compared to the control (DI water). The NO3− and NO2− contents increased, resulting in an increase in total nitrogen (N) and gibberellic acid (GA3) accumulation in rice seeds. The PAW at an airflow rate of 5 L/min was optimal for enhancing radicle emergence at 48 and 72 h, germination, germination index, shoot length, fresh weight, and dry weight of seedlings. Therefore, air GA plasma to generate PAW is an efficient method for producing nitrogen in a soluble form, which can support the germination processes and early growth of rice seedlings.

How a natural antibiotic uses oxidative stress to kill oxidant-resistant bacteria.

Natural products that possess antibiotic and antitumor qualities are often suspected of working through oxidative mechanisms. In this study, two quinone-based small molecules were compared. Menadione, a classic redox-cycling compound, was confirmed to generate high levels of reactive oxygen species inside Escherichia coli. It inactivated iron-cofactored enzymes and blocked growth. However, despite the substantial levels of oxidants that it produced, it was unable to generate significant DNA damage and was not lethal. Streptonigrin, in contrast, was poorer at redox cycling and did not inactivate enzymes or block growth; however, even in low doses, it damaged DNA and killed cells. Its activity required iron and oxygen, and in vitro experiments indicated that its quinone moiety transferred electrons through the adjacent iron atom to oxygen. Additionally, in vitro experiments revealed that streptonigrin was able to damage DNA without inhibition by catalase, indicating that hydrogen peroxide was not involved. We infer that streptonigrin can reduce bound oxygen directly to a ferryl species, which then oxidizes the adjacent DNA, without release of superoxide or hydrogen peroxide intermediates. This scheme allows streptonigrin to kill a bacterial cell without interference by scavenging enzymes. Moreover, its minimal redox-cycling behavior avoids alerting either the OxyR or the SoxRS systems, which otherwise would block killing. This example highlights qualities that may be important in the design of oxidative drugs. These results also cast doubt on proposals that bacteria can be killed by stressors that merely stimulate intracellular O2- and H2O2 formation.

Catalyst-Free Carbon Dioxide Conversion in Water Facilitated by Pulse Discharges.

By inducing CO2-pulsed discharges within microchannel bubbles and regulating thus-forming plasma microbubbles, we observe high-performance, catalyst-free coformation of hydrogen peroxide (H2O2) and oxalate directly from CO2 and water. With isotope-labeled C18O2 as the feedstock, peaks of H218O16O and H216O2 observed by ex situ surface-enhanced Raman spectra indicate that single-atom oxygen (O) from CO2 dissociations and H2O-derived OH radicals both contribute to H2O2 formation. The global plasma chemistry modeling suggests that high-density, energy-intense electron supply enables high-density CO2- (aq) and HCO2- (aq) formation and their subsequent coupling to produce oxalate. The enhanced solvation of CO2, facilitated by the efficient transport of CxOy ionic species and CO, is demonstrated as a crucial benefit of spark discharges interacting with water at the bubble interface. We expect this plasma microbubble approach to provide a novel power-to-chemical avenue to convert CO2 into valuable H2O2 and oxalic acid platform chemicals, thus leveraging renewable energy resources.

Recording changes in biochemical parameters &lt;i&gt;in vivo&lt;/i&gt; in the ischemic stroke model

Stroke is a significant and socially insidious disease that ranks second among fatal diseases according to the World Health Organization [1]. Understanding the molecular mechanisms behind the pathogenesis of this ailment will enable the development of more effective preventative measures and treatment strategies to minimize the negative consequences of stroke. Despite the abundance of experimental data, most of which were acquired indirectly, the study of the dynamics of biochemical parameters in brain tissue in real time during the acute phase of ischemic stroke is difficult. The use of genetically-encoded sensors creates novel possibilities for monitoring alterations in different biochemical and metabolic parameters in vivo tissues. In this study, we evaluated pH changes, hydrogen peroxide production (an important type of biologically active ROS), and polysulfide synthesis in various types of brain tissue cells of SHR rats during the development of ischemic stroke in real time using sensors such as SypHer3s (for pH detection), HyPer7 (for H2O2 detection), and PersIc (for polysulfide detection). Middle cerebral artery occlusion was used to simulate an ischemic stroke. The in vivo sensor signals were registered with a fiber optic setup that was created in the laboratory of spectroscopy and nonlinear optics at Moscow State University. The studies revealed that in the acute phase of stroke, acidosis occurred in the cytoplasm of neurons in the caudate nucleus, the epicenter of ischemia. The pH mutated from 7.25±0.08 to 6.7±0.15 within the first few seconds after arterial occlusion initiation. A gradual increase in pH was observed after the initial drop, which persisted throughout reperfusion but did not return to the original value in all animals. In the penumbra zone, a wave-like shift in sensor signal was detected, whereas no change in sensor signal was noted in the healthy hemisphere. Investigation of the dynamics of H2O2 formation in the mitochondrial matrix of caudate neurons revealed minimal sensor oxidation during ischemia/reperfusion in the acute phase of stroke, indicating low ROS production. Nevertheless, a substantial increase in the sensor signal was detected after 24 hours following the surgery. Thus, the confirmation of oxidative stress development in the affected hemisphere differed from the commonly accepted view in terms of its dynamics. Previously, it was believed that excessive production of H2O2 leading to oxidative stress and related brain cell death occurred primarily in the acute phase. However, a comparison of hydrogen peroxide production dynamics in neurons and astrocytes revealed differences between these cell populations. It was discovered that as early as 12 hours after middle cerebral artery occlusion, the sensor signal in astrocytes increased more intensely than in neurons. This trend persisted until the end of the measurements, 40 hours after surgery. The observed distinctions may stem from glial cells’ protective function in counteracting the harmful consequences of hydrogen peroxide on neurons, along with their contribution to maintaining the myelin structure in the brain. Additionally, the role of astrocytes in neuroinflammation development is noteworthy. Reactive sulfur species, in addition to reactive oxygen species, appear to be significant contributors to the development of pathological processes. The PersIc sensor signal measurement did not show any disparities between the caudate nucleus of the healthy hemisphere and the hemisphere affected by stroke development in terms of polysulfide and persulfide appearance detection. However, the area surrounding the core infarction is noteworthy due to the observed bouts of acidosis using the SypHer3s sensor. Our findings suggest a potential association between these bouts, spreading depolarization, changes in calcium concentration, and the development of neuroinflammation. These reactions may ultimately lead to the synthesis of polysulfides, known modulators of inflammatory reactions. Thus, our data provides valuable additions to the existing knowledge on metabolic changes that take place during the progression of ischemic brain injury.

Photocatalytic H2 O2 Generation Reaction with a Benchmark Rate at Air-Liquid-Solid Joint Interfaces.

The rapid charge recombination, low selectivity for two-electron oxygen reduction reaction (ORR), and limited O2 diffusion rate hinder the practical applications of photocatalytic H2 O2 generation. Herein, a triphase photocatalytic system in which the H2 O2 generation occurs at the air-liquid-solid joint interfaces is developed, using polymeric carbon nitride (PCN). The introduction of pyrrole units and cyano group into PCN can promote the activation of oxygen molecules and facilitate the spatial separation of HOMO and LUMO orbits, hence improving the charge carrier separation efficiency and enhancing the formation of H2 O2 . Importantly, the gas-liquid-solid triphase interface system allows for the rapid transport of oxygen from the air to the reaction interface, overcoming the low solubility and slow diffusion of oxygen in the water in conventional liquid reaction systems. The triphase system shows a benchmark H2 O2 generation rate over PCN-based materials in pure water (2063.21µmol g-1 h-1 ), which is an approximate tenfold enhancement as compared to powder photocatalyst (215.44µmol g-1 h-1 ). Simulation and electrochemical tests reveal that the rapid oxygen diffusion rate of triphase interface can promote charge separation and provide more O2 to generate H2 O2 . This work provides a promising strategy for constructing an efficient and sustainable H2 O2 production system.