Reactive Radical Species Research Articles

Application of a Film Model to Mass Transfer and Chemical Reaction at a Plasma-Liquid Interface

Plasma electrodes provide novel ways of conducting electrochemical processes in liquids, in particular because of the ability to generate unique reactive radical species. However, the radicals injected into the liquid and their ensuing reactions are often confined to a narrow region near the interface of the plasma and the liquid. Thus, mass transfer has been found to play an important role in the observed kinetics and a modeling framework that includes both transport and kinetics is required to interpret experimental data. Here, we apply the idea of a film model for interphase mass transfer to plasma-liquid electrochemical processes, whereby transport is described by a stagnant film that is inherently linked to the concentration boundary layer and the mass transfer coefficient. Equations that govern the transport and reaction of radicals and substrates within the film are solved assuming a quasi-steady state approximation. The model is applied to specific case studies from the literature to estimate important parameters that are difficult to measure experimentally, such as the mass transfer coefficient. Our study shows that a film model can elucidate the effect of mass transfer on observed conversion rates and allow the intrinsic kinetics to be unraveled.

The role of BaTiO3 nanoparticles as photocatalysts in the synthesis and characterization of novel fruit dyes is investigated.

In the present work, the photocatalytic activity against the natural dye extracted from the novel fruits has been studied by the BaTiO3 nanoparticles (NPs) under a ultra-violet (UV) light source. The large concentrations of an essential phenolic agent present in this phytochemical extract superimposed with cloths fibers make strong stain and degrade into another form of toxic, which is excluded from the many textiles industries as the colorful waste waters without recycling and removal of that dye pigments have been investigated using both photodegradation and photoluminescence techniques. The entitled nanoparticles (NPs) were prepared using the soft chemical root-modified solvothermal synthesis combo method and exposure to heat treatment such that the annealing process has been done for different temperatures ranging from 100°C to 250°C. As for as concern the characterization, as a start, structural and morphology studies have been reported here that highly crystalline oriented peaks data using powder x-ray diffraction techniques (PXRD) as well as the surface morphology including the size, shape, and mass distribution using the field emission scanning electron microscopy (FESEM) techniques, which purely belong to rutile tetragonal structure of the crystal system and circular and noncircular flakes like rough surface morphology materials respectively. The lattice dissociation constant 'ε' value of the BaTiO3 NPs has determined to be ~2.71 × 10-3 using the Williamson-Hall (W-H plot) analysis of crystallographic data. In the UV visible spectroscopy findings, since the extreme quantum confinement of BaTiO3 nanoflakes/nanodisc, the optical energy bandgap has been estimated to be a range of 1.98 to 2.67 eV (~2.48 eV) found from the Tauc plot analysis, which contributes to the significantly owing to the enhanced photocatalytic efficiency with excellent performance along exciton formation, superoxide ions, and hydroxyl free radicals generations under UV-vis light irradiation resulting in efficient degradation of typical novel fruit organic dye. Photoluminescence spectra observed at room temperature and low temperature have been observed for the BaTiO3 nanoflakes, which exhibit the blue emission due to the crystalline defects such as the appearance of Ba vacancies leads to the conceivable beginning of p-type conductivity and the origination of free exciton emission reveals the direct bandgap transition nature of nanoflakes. RESEARCH HIGHLIGHTS: According to our findings, 89.71% of the natural syzygium cumin is degraded by photocatalysis reaction. As a plausible mechanism for the destruction of natural dyes under solar light, photocatalytic destruction has been proposed. The reaction between these reactive free radical species leads to high efficiency photodegradation with a short decay time. In addition to water treatment and environmental cleaning applications, the excellent performance of this photocatalyst makes it a promising candidate for other applications. Hence, the synthesized BaTiO3 nanoflakes showcase a highly significant advancement towards the development of a textiles dye recycling method.

Spontaneous formation of reactive redox radical species at the interface of gas diffusion electrode

The aqueous interface-rich system has been proposed to act as a trigger and a reservoir for reactive radicals, playing a crucial role in chemical reactions. Although much is known about the redox reactivity of water microdroplets at “droplets-in-gas” interfaces, it remains poorly understood for “bubbles-in-water” interfaces that are created by feeding gas through the porous membrane of the gas diffusion electrode. Here we reveal the spontaneous generation of highly reactive redox radical species detected by using electron paramagnetic resonance under such conditions without applying any bias and loading any catalysts. In combination with ultraviolet-visible spectroscopy, the redox feature has been further verified through several probe molecules. Unexpectedly, introducing crown ether allows to isolate and stabilize both water radical cations and hydrated electrons thus substantially increasing redox reactivity. Our finding suggests a reactive microenvironment at the interface of the gas diffusion electrode owing to the coexistence of oxidative and reductive species.

Role of CTAB, and reactive radical species (HO[rad] and O2−[rad]) on the permanganate redox reaction

Permanganate-H2SO4 redox system was used to establish the role of cetyltrimethylammonium bromide (CTAB), and reactive radical species on the oxidative degradation of Congo red. The absorbance at 496 nm increases for ca. 6.0 min, and then decreases. Permanganate-Congo red redox reaction was very slow (degradation efficiency = 46 % in 180 min with kobs = 0.004 min−1 at 496 nm). The degradation efficiency was found to be 85 % in 6.0 min of reaction time with H2SO4. Congo red and permanganate interact with CTAB aggregates due to the electrostatic interactions. The decay of absorbance at 467 nm became very slow with increasing CTAB concentrations. The oxidative treatment of Congo red/MnO4− system follows first-, and complex – order kinetics with permanganate, and Congo red concentrations, respectively. The Congo red degradation efficiency remains unaffected with sodium pyrophosphate and sodium fluoride, which ruled out the possibility of Mn(III) formation as an oxidation state of manganese. Humic acid (HA) enhanced the degradation efficiency of Congo red/MnO4− system, and facilitated the in-situ formation of water soluble colloidal MnO2. The scavenger’s studies revealed that hydroxyl (HO), and superoxide (O2−) radicals were not the reactive species in the Congo red/ MnO4− redox system under our experimental conditions.

Quantum-enhanced photoprotection in neuroprotein architectures emerges from collective light-matter interactions

BackgroundSuperradiance is the phenomenon of many identical quantum systems absorbing and/or emitting photons collectively at a higher rate than any one system can individually. This phenomenon has been studied analytically in idealized distributions of electronic two-level systems (TLSs), each with a ground and excited state, as well as numerically in realistic photosynthetic nanotubes and cytoskeletal architectures.MethodsSuperradiant effects are studied here in idealized toy model systems and realistic biological mega-networks of tryptophan (Trp) molecules, which are strongly fluorescent amino acids found in many proteins. Each Trp molecule acts as a chromophore absorbing in the ultraviolet spectrum and can be treated approximately as a TLS, with its 1La excited singlet state; thus, organized Trp networks can exhibit superradiance. Such networks are found, for example, in microtubules, actin filaments, and amyloid fibrils. Microtubules and actin filaments are spiral-cylindrical protein polymers that play significant biological roles as primary constituents of the eukaryotic cytoskeleton, while amyloid fibrils have been targeted in a variety of neurodegenerative diseases. We treat these proteinaceous Trp networks as open quantum systems, using a non-Hermitian Hamiltonian to describe interactions of the chromophore network with the electromagnetic field. We numerically diagonalize the Hamiltonian to obtain its complex eigenvalues, where the real part is the energy and the imaginary part is its associated enhancement rate. We also consider multiple realizations of increasing static disorder in either the site energies or the decay rates.ResultsWe obtained the energies and enhancement rates for realistic microtubules, actin filament bundles, and amyloid fibrils of differing lengths, and we use these values to calculate the quantum yield, which is the ratio of the number of photons emitted to the number of photons absorbed. We find that all three of these structures exhibit highly superradiant states near the low-energy portion of the spectrum, which enhances the magnitude and robustness of the quantum yield to static disorder and thermal noise.ConclusionThe high quantum yield and stable superradiant states in these biological architectures may play a photoprotective role in vivo, downconverting energetic ultraviolet photons—absorbed from those emitted by reactive free radical species—to longer, safer wavelengths and thereby mitigating biochemical stress and photophysical damage. Contrary to conventional assumptions that quantum effects cannot survive in large biosystems at high temperatures, our results suggest that macropolymeric collectives of TLSs in microtubules, actin filaments, and amyloid fibrils exhibit increasingly observable and robust effects with increasing length, up to the micron scale, due to quantum coherent interactions in the single-photon limit. Superradiant enhancement and high quantum yield exhibited in neuroprotein polymers could thus play a crucial role in information processing in the brain, the development of neurodegenerative diseases such as Alzheimer’s and related dementias, and a wide array of other pathologies characterized by anomalous protein aggregates.

Chemical-Free Stable and Multifunctional Electro-Based System for Treatment of Pesticides from Aqueous Solution

The usage of pesticides has become a common practice in modern agricultural systems to meet the growing demand for food production. However, the uncontrolled use of such chemicals results in the deterioration of natural ecosystems and living beings. Thus, herein, a hybrid treatment system performing the combined functions of electro- and photo Fenton was designed to treat aqueous pesticide solution. The anode was comprised of metal oxide-based electrode (MOx), whereas the cathode was comprised of N-doped carbon electrode (N-C). Both the electrodes consist of light-responsive photocatalysts, which facilitates the removal of pollutants by generating reactive radical species such as OH• and O2 •-. The application of external anodic bias helps to improve the photocatalytic activity by preventing the recombination of electron-hole pairs. In addition, N-C on the cathode helps to catalyze the reduction of O2 to H2O2, which further reacts with Fe2+ in the system to initiate the Fenton reaction. The hybrid reactor was further optimized to study the underlying mechanisms by varying the experimental conditions such as pH, current density, electrolyte concentration, and external H2O2 concentration.Moreover, scavenging tests were performed using methanol and tertbutyl alcohol to identify the predominant radical species responsible for removing pollutants from the aqueous solution. Also, the reusability test showed that the prepared electrodes were stable for more than three successive cycles, thus offering sustainability. In general, the present study demonstrates the potential of hybrid treatment units for environmental applications and acts as a stepping stone for future endeavors in material synthesis and sustainable treatment solutions.

Enter MnIV-NHC: A Dark Photooxidant with a Long-Lived Charge-Transfer Excited State.

Detailed photophysical investigation of a Mn(IV)-carbene complex has revealed that excitation into its lowest-energy absorption band (∼500 nm) results in the formation of an energetic ligand-to-metal charge-transfer (LMCT) state with a lifetime of 15 ns. To the best of our knowledge, this is the longest lifetime reported for charge-transfer states of first-row-based transition metal complexes in solution, barring those based on Cu, with a d10 configuration. A so-called superoxidant, Mn(IV)-carbene exhibits an excited state potential typically only harnessed via excited states of reactive organic radical species. Furthermore, the long-lived excited state in this case is found to be a dark doublet, with its transition to the quartet ground state being spin-forbidden, a contrast to most first-row literature examples, and a possible cause of the long lifetime. Showcasing excited state properties which in some cases exceed those of complexes based on precious metals, these findings not only advance the library of earth-abundant photosensitizers but also shed general insight into the photophysics of d3 and related Mn complexes.

Water mediated redox-neutral cleavage of arylalkenes via photoredox catalysis

Cleavage of carbon-carbon bonds remains a challenging task in organic synthesis. Traditional methods for splitting Csp2=Csp2 bonds into two halves typically involve non-redox (metathesis) or oxidative (ozonolysis) mechanisms, limiting their synthetic potential. Disproportionative deconstruction of alkenes, which yields one reduced and one oxidized fragment, remains an unexplored area. In this study, we introduce a redox-neutral approach for deleting a Csp2 carbon unit from substituted arylalkenes, resulting in the formation of an arene (reduction) and a carbonyl product (oxidation). This transformation is believed to proceed through a mechanistic sequence involving visible-light-promoted anti-Markovnikov hydration, followed by photoredox cleavage of Csp3-Csp3 bond in the alcohol intermediate. A crucial consideration in this design is addressing the compatibility between the highly reactive oxy radical species in the latter step and the required hydrogen-atom-transfer (HAT) reagent for both steps. We found that ethyl thioglycolate serves as the optimal hydrogen-atom shuttle, offering remarkable chemoselectivity among multiple potential HAT events in this transformation. By using D2O, we successfully prepared dideuteromethylated (-CD2H) arenes with good heavy atom enrichment. This work presents a redox-neutral alternative for alkene deconstruction, with considerable potential in late-stage modification of complex molecules.

Ag0, Re0, and Ag@Re heterogeneous persulfate activators for reactive radical based oxidation of water contaminant

Silver-rhenium bi-metallic nanoparticles (Ag-Re) were prepared by the combination of colloidal sols of silver and rhenium at room temperature. The silver and rhenium sols were synthesized by using the chemical reduction of silver nitrate and ammonium perrhenate with sodium borohydride in presence of cetyltrimethylammonium bromide (CTAB). The morphology (shape, size, elemental composition, oxidation states, and crystalline nature) and textural properties (pore size, pore volume, and surface area) of Ag0-Re0 were determined with EDX, SEM, TEM, XPS, XRD, and nitrogen adsorption-desorption isotherm. The Ag0-Re0 was used as heterogeneous persulfate (S2O82−) activator to generate reactive radical species (SO4−• and HO•) for the degradation of xylenol orange (XO) at 434 nm. The Ag-Re exhibits higher XO degradation efficiency than that of mono-metallic Ag0 and Re0 nanoparticles, respectively. The degradation efficiency strongly depends on the concentrations of S2O82−, XO, pH, temperature, and amount of Ag0-Re0. The role of SO4−• and HO• were established by using ethanol, and tertiary butanol as radical scavengers. The activation energy was found to be 85.2, 63.5, and 32.6 kJ/mol, respectively, to the degradation of XO by activated S2O82− with Re0, Ag0, and Ag0-Re0.

Insight into the sulfite activation by Fe-rich sludge-derived biochar for efficient organic contaminant degradation: The role of iron species

Sulfate radical-based advanced oxidation processes driven by sulfite [S(IV)] activation offer a sustainable and cost-effective approach for environmental remediation. The utilization of abundant iron oxide species in Fe-rich sludge for S(IV) activation presents a cost-effective and eco-friendly solution, making it an attractive option for Fe-rich sludge disposal and water treatment. Herein, an efficient S(IV) activation system was developed by using Fe-rich sludge-derived biochar (FBC) for the first time. The performance of S(IV) activation by different pyrolyzed FBCs was evaluated in terms of tetracycline (TC) degradation. The highest degradation efficiency of TC was achieved 95.0 % in the S(IV)/FBC700 under the optimum conditions. The reactive radical species responsible for TC degradation in the system were confirmed to be SO4•−. The present work opens up new possibilities for the development of novel advanced oxidation processes utilizing the waste Fe-rich sludge.

Radical-mediated oxidative desulfurization of dibenzothiophene in a chromophore-enhanced photocatalytic system

This study presents a refined photocatalytic oxidative desulfurization (PODS) approach, leveraging a chromophore-enhanced system specifically designed for the selective degradation of dibenzothiophene (DBT). Employing a ruthenium-based complex (RuL) as a model sensitizer that can be activated by visible light, the system catalytically decomposes peroxydisulfate (S2O82−) into highly reactive radical species, key agents in facilitating efficient sulfur oxidation. In this system, the oxidative degradation of DBT proceeds through a well-defined pathway, sequentially transforming DBT into its sulfoxide (DBT-O) and subsequently into its sulfone (DBT-O2) derivatives, achieving nearly complete conversion to DBT-O2. The electron transfer dynamics within this photocatalytic system are examined through a concentration-dependent decrease in photoluminescence. Moreover, the effects of various electron donors and acceptors on the system’s catalytic activity, as well as the influence of structural modifications of the ruthenium sensitizer are investigated. Comparative evaluations with an alternative 9,10-dicyanoanthracene (DCA)-sensitized system underscore the superior efficiency and selectivity of the sulfate and/or hydroxyl radicals generated in the RuL/S2O82− system. Unlike the superoxide radicals produced in the DCA-sensitized system, the radicals generated in the RuL/S2O82− system exhibit significantly enhanced kinetics for DBT oxidation. The RuL/S2O82− photocatalytic system operates effectively under milder conditions without requiring hydrogen, positioning it as a promising alternative for sulfur removal and potentially contributing to more environmentally sustainable and economically viable fuel processing technologies.

The Bacillus subtilis yqgC-sodA operon protects magnesium-dependent enzymes by supporting manganese efflux.

Microbes encounter a myriad of stresses during their life cycle. Dysregulation of metal ion homeostasis is increasingly recognized as a key factor in host-microbe interactions. Bacterial metal ion homeostasis is tightly regulated by dedicated metalloregulators that control uptake, sequestration, trafficking, and efflux. Here, we demonstrate that deletion of the Bacillus subtilis yqgC-sodA (YS) complex operon, but not deletion of the individual genes, causes hypersensitivity to manganese (Mn). YqgC is an integral membrane protein of unknown function, and SodA is a Mn-dependent superoxide dismutase (MnSOD). The YS strain has reduced expression of two Mn efflux proteins, MneP and MneS, consistent with the observed Mn sensitivity. The YS strain accumulated high levels of Mn, had increased reactive radical species (RRS), and had broad metabolic alterations that can be partially explained by the inhibition of Mg-dependent enzymes. Although the YS operon deletion strain and an efflux-deficient mneP mneS double mutant both accumulate Mn and have similar metabolic perturbations, they also display phenotypic differences. Several mutations that suppressed Mn intoxication of the mneP mneS efflux mutant did not benefit the YS mutant. Further, Mn intoxication in the YS mutant, but not the mneP mneS strain, was alleviated by expression of Mg-dependent, chorismate-utilizing enzymes of the menaquinone, siderophore, and tryptophan (MST) family. Therefore, despite their phenotypic similarities, the Mn sensitivity in the mneP mneS and the YS deletion mutants results from distinct enzymatic vulnerabilities.IMPORTANCEBacteria require multiple trace metal ions for survival. Metal homeostasis relies on the tightly regulated expression of metal uptake, storage, and efflux proteins. Metal intoxication occurs when metal homeostasis is perturbed and often results from enzyme mis-metalation. In Bacillus subtilis, Mn-dependent superoxide dismutase (MnSOD) is the most abundant Mn-containing protein and is important for oxidative stress resistance. Here, we report novel roles for MnSOD and a co-regulated membrane protein, YqgC, in Mn homeostasis. Loss of both MnSOD and YqgC (but not the individual proteins) prevents the efficient expression of Mn efflux proteins and leads to a large-scale perturbation of the metabolome due to inhibition of Mg-dependent enzymes, including key chorismate-utilizing MST (menaquinone, siderophore, and tryptophan) family enzymes.

Peroxymonosulfate-activated photocatalytic degradation of norfloxacin via a dual Z-scheme g-C3N5/BiVO4/CoFe − LDH heterojunction: Operation and mechanistic insights

The design of novel dual Z-scheme heterojunction plays a significant path in eradicating organic contaminants via enriched charge carrier separation. Herein, a wet chemical method was used to synthesize ternary g-C3N5/BiVO4/CoFe–LDH (CBCF) nanocomposites, and their corresponding abilities were characterized as follows: crystal phases, optical properties, surface morphologies, and compositions. The g-C3N5/BiVO4/CoFe–LDH-30% (CBCF-3) sample optimized the removal efficiency of norfloxacin (NOR) by up to 95.3% through peroxymonosulfate (PMS) activation in a visible light medium. The combined effects from the Vis/PMS/CBCF-3 catalytic system led to 7-times higher degradation efficiency than visible light only system. This improved performance was attributed to the generation of reactive radical species because of higher PMS utilization and an effective Z-charge transfer process from well-oriented band structures. Moreover, scavenging tests and electron spin resonance analysis revealed the production of active radical and non-radical species, namely •OH, SO4•−, •O2−, and 1O2. Based on the appropriate experimental analysis, the expected NOR degradation mechanism and possible pathways were proposed. Then, the toxicity evaluation results revealed that the intermediate products may not have an adverse effect on the aquatic ecosystems. This research study provides a positive outcome for wastewater remediation using enriched dual Z-scheme mechanism.

Comprehensive kinetic investigation of antiradical activity of urolithins and their potential inhibitory effect on Xanthine Dehydrogenase

This work aimed to explore the antiradical activity of various ellagitannin metabolites, including Urolithin A (UroA), Urolithin B (UroB), Urolithin C (UroC), and Urolithin D (UroD), in a non-polar (benzene) and polar (water) medium. The antiradical effect of the investigated compounds against reactive oxygen species HO• was evaluated in water (physiological conditions) and benzene, while against CH3OO• and CCl3OO• it was assessed solely in benzene, using the Quantum Mechanics-based Test for Overall Free-radical Scavenging Activity (QM-ORSA) methodology. In non-polar media, compounds UroA, UroC, and UroD exhibit antiradical capabilities against the HO• through Proton-coupled electron transfer (PCET) and Radical Adduct Formation (RAF) processes. Conversely, UroB predominantly exhibits inhibitory activity on HO• through the RAF pathway. On the other hand, the reaction with CH3OO• and CCl3OO• only occurs through the Hydrogen Atom Transfer (HAT). Under physiological conditions, all investigated compounds show antiradical capacity against the HO•, primarily via the SPLET and RCF mechanisms. The reactivity of radical species in both solvents decreases in the following order: HO• > CCl3OO• > CH3OO•. The thermodynamic and kinetic parameters in both solvents indicate that the investigated compounds’ reactivity follows a decreasing order of UroD > UroA > UroC > UroB. Furthermore, newly formed radical species of urolithin exhibit lower reactivity towards the fatty acid model in comparison to investigated reactive radical species, potentially preventing lipid peroxidation initiation. The investigated compounds can regenerate glutathione (GSH) by providing a hydrogen atom to the glutathione radical (GS•), which forms during interaction with highly reactive radical species. In water, tested compounds also regenerate GSH by donating H atoms to GS•, as well as by transferring electrons from dominant acid-base species to GS•, followed by protonation of the resulting GS¯. Urolithins showed similar inhibitory effects as the conventional inhibitors Y-700, FYX-051, and Febuxostat on Xanthine Dehydrogenase (XDH). Reactivity towards XDH enzyme decreases in the following order UroC > UroB > UroD > UroA.

Identifying Radical Pathways for Cu(I)/Cu(II) Relay Catalyzed Oxygenation via Online Coupled EPR/UV-Vis/Near-IR Monitoring.

Copper-catalyzed C─H oxygenation has drawn considerable attention in mechanistic studies. However, a comprehensive investigation combining radical pathways with a metal-catalytic cycle is challenged by the intricate organic radicals and metallic intermediates. Herein, an online coupled EPR/UV-vis/near-IR detecting method is developed to simultaneously monitor both reactive radical species and copper complex intermediates during the reaction. Focusing on copper-catalyzed phenol oxygenation with cumene hydroperoxide, the short-lived alkylperoxyl radical (EPR signal at g=2.0143) as well as the unexpected square planar Cu(II)-alkoxyl radical complex (near-IR signal at 833nm) are unveiled during the reaction, in addition to the observable phenoxyl radical in EPR, quinone product in UV-vis, and Cu(II) center in EPR. With a comprehensive picture of diverse intermediates evolving over the same timeline, a novel Cu(I)/Cu(II) proposed relay-catalyzed sequential radical pathway. In this sequence, Cu(II) activates hydroperoxide through Cu(II)-OOR into the alkylperoxide radical, while the reaction between Cu(I) and hydroperoxide leads to Cu(II)(•OR)OH with high H-atom abstracting activity. These results provide a thorough understanding of the Cu(I)/Cu(II) relay catalysis for phenol oxygenation, setting the stage for mechanistic investigations into intricate radical reactions promoted by metallic complexes.

Exploring enzyme inhibition and comprehensive mechanisms of antioxidant/prooxidative activity of natural furanocoumarin derivatives: A comparative kinetic DFT study

This study aimed to explore the antioxidant and prooxidative activity of two natural furanocoumarin derivatives, Bergaptol (4-Hydroxy-7H-furo [3,2-g] [1]benzopyran-7-one, BER) and Xanthotoxol (9-Hydroxy-7H-furo [3,2-g] [1]benzopyran-7-one, XAN). The collected thermodynamic and kinetic data demonstrate that both compounds possess substantial antiradical activity against HO• and CCl3OO• radicals in physiological conditions. BER exhibited better antiradical activity in comparison to XAN, which can be attributed to the enhanced deprotonation caused by the positioning of the –OH group on the psoralen ring. In contrast to highly reactive radical species, newly formed radical species BER• and XAN• exhibited negligible reactivity towards the chosen constitutive elements of macromolecules (fatty acids, amino acids, nucleobases). Furthermore, in the presence of O2•─, the ability to regenerate newly formed radicals BER• and XAN• was observed. Conversely, in physiological conditions in the presence of Cu(II) ions, both compounds exhibit prooxidative activity. Nevertheless, the prooxidative activity of both compounds is less prominent than their antioxidant activity. Furthermore, it has been demonstrated that anionic species can engage in the creation of a chelate complex, which restricts the reduction of metal ions when reducing agents are present (O2•─ and Asc─). Moreover, studies have demonstrated that these chelating complexes can be coupled with other radical species, hence enhancing their ability to inactivate radicals. Both compounds exhibited substantial inhibitory effects against enzymes involved in the direct or indirect generation of ROS: Xanthine Oxidase (XOD), Lipoxygenase (LOX), Myeloperoxidase (MPO), NADPH oxidase (NOX).

Diethyldithiocarbamate-ferrous oxide nanoparticles inhibit human and mouse glioblastoma stemness: aldehyde dehydrogenase 1A1 suppression and ferroptosis induction.

The development of effective therapy for eradicating glioblastoma stem cells remains a major challenge due to their aggressive growth, chemoresistance and radioresistance which are mainly conferred by aldehyde dehydrogenase (ALDH)1A1. The latter is the main stemness mediator via enhancing signaling pathways of Wnt/β-catenin, phosphatidylinositol 3-kinase/AKT, and hypoxia. Furthermore, ALDH1A1 mediates therapeutic resistance by inactivating drugs, stimulating the expression of drug efflux transporters, and detoxifying reactive radical species, thereby apoptosis arresting. Recent reports disclosed the potent and broad-spectrum anticancer activities of the unique nanocomplexes of diethyldithiocarbamate (DE, ALDH1A1 inhibitor) with ferrous oxide nanoparticles (FeO NPs) mainly conferred by inducing lipid peroxidation-dependent non-apoptotic pathways (iron accumulation-triggered ferroptosis), was reported. Accordingly, the anti-stemness activity of nanocomplexes (DE-FeO NPs) was investigated against human and mouse glioma stem cells (GSCs) and radioresistant GSCs (GSCs-RR). DE-FeO NPs exhibited the strongest growth inhibition effect on the treated human GSCs (MGG18 and JX39P), mouse GSCs (GS and PDGF-GSC) and their radioresistant cells (IC50 ≤ 70 and 161μg/mL, respectively). DE-FeO NPs also revealed a higher inhibitory impact than standard chemotherapy (temozolomide, TMZ) on self-renewal, cancer repopulation, chemoresistance, and radioresistance potentials. Besides, DE-FeO NPs surpassed TMZ regarding the effect on relative expression of all studied stemness genes, as well as relative p-AKT/AKT ratio in the treated MGG18, GS and their radioresistant (MGG18-RR and GS-RR). This potent anti-stemness influence is primarily attributed to ALDH1A1 inhibition and ferroptosis induction, as confirmed by significant elevation of cellular reactive oxygen species and lipid peroxidation with significant depletion of glutathione and glutathione peroxidase 4. DE-FeO NPs recorded the optimal LogP value for crossing the blood brain barrier. This in vitro novel study declared the potency of DE-FeO NPs for collapsing GSCs and GSCs-RR with improving their sensitivity to chemotherapy and radiotherapy, indicating that DE-FeO NPs may be a promising remedy for GBM. Glioma animal models will be needed for in-depth studies on its safe effectiveness.

PFAS degradation by anodic electrooxidation: Influence of BDD electrode configuration and presence of dissolved organic matter

Per- and poly-fluoroalkyl substances (PFAS) pose substantial environmental and human health risks. Electrochemical oxidation technology is a promising large-scale solution for PFAS degradation due to its simplicity and minimal waste generation. This study investigated the electrochemical performance of boron-doped diamond (BDD) electrodes in degrading PFAS using a recirculation cell with plate and mesh electrodes. The study found that increasing the current density from 6.4 mA/cm2 to 40 mA/cm2 resulted in a transition of the reaction rate from pseudo-first-order toward zero-order kinetics. The stepwise degradation mechanism and the formation of intermediate products were also explored. Carbon and fluorine molar balance analysis revealed that the missing intermediates do not contain fluoride atoms in their molecular formula. The shape and surface of the electrodes had a significant impact on their performance, in particular, improving the degradation of the most recalcitrant perfluorobutanoic acid. The influence of different fractions of dissolved organic matter (DOM) on perfluorohexanoic acid degradation shows that overall, DOM does not significantly inhibit its degradation. Some inhibition was observed in the presence of DOM enriched in carbohydrates, organics that are known to exert strong interaction properties with organic and inorganic surfaces. The synergistic effect of direct anodic oxidation and indirect degradation by reactive radical species enables the decomposition of both DOM and PFAS. Finally, high removal percentages of short (up to 96 %) and long-chain PFAS (up to 99 %) were obtained using BDD electrooxidation cells combining plate and mesh electrodes when treating reverse osmosis concentrate containing PFAS.

Numerical investigation of premixed combustion of producer gas with hydrogen injection in a cyclonical chamber

ABSTRACT This paper employs computational fluid dynamics (CFD) simulations with an eddy dissipation concept model (EDC) and a skeletal reaction mechanism (SK17) to analyze the impact of hydrogen addition on the premixed combustion mode of producer gas (PG) fuel in a cyclonic flow combustion chamber. The results, validated against measured wall temperature data, demonstrate a minor discrepancy between simulation and experiment. The studied result showed that injection of hydrogen into PG fuel combustion elevates the temperature of the combustion process, which can be indicated by the average temperature across the combustion chamber, outlet temperature of exhaust gas, and reactive radical species. However, increasing H2 injection over 20% results in strongly increasing CO formations. Compared to a fixed thermal input case, hydrogen injection with a variable input power resulted in a higher combustion temperature and increased emissions of both CO and NO. The maximum CO emission reached approximately 1246 ppm, while NO peaked at around 75 ppm, both observed at a 30% hydrogen injection rate. The key finding of this study revealed that direct injection of hydrogen to the combustion under the condition of a given equivalence ratio is unfavorable due to insufficient oxygen for the reaction, leading to an increase in CO emissions. The optimal condition would be a hydrogen injection below 20%, which produces low CO and NO emissions.

Harnessing Protein Waste into Reduced Graphitic Carbon Oxide‐Copper‐Collagen Nanocomposite for Visible Light Photocatalytic Degradation of Nano Plastics

AbstractNano and micro plastics are harmful to the aqueous environment and the current treatment systems are either ineffective or expensive, which restricts their widespread use. In this research, reduced graphitic carbon oxide (rGO)‐Cu nanoparticles crosslinked with collagen support (rGO‐Cu/Coll) are employed as an efficient photocatalyst for the degradation of polystyrene (PS) nano plastics in water. It is shown that rGO‐Cu/Coll nanocomposite can degrade PS nano plastics when subjected to simulated visible light and direct sunlight. In the photocatalytic degradation of PS nano plastics, the reactive radical species (•OH and O2•−) produced on the surfaces of rGO‐Cu/Coll nanocomposite materials play major roles in de‐polymerization. The investigation of the FESEM, Raman, and UV–vis spectra of the irradiated and non‐irradiated samples reveal observable changes, including the distorted morphology and formation of a new band, with longer exposure times and greater degradation. Additionally, evidence for the photodegradation of PS chains is demonstrated by the observed increase in the intensities of the carboxylate, carbonyl, and hydroxyl absorption regions of the ATR‐FTIR spectra. The study provides a simple approach to the battle against plastic pollution in aquatic ecosystems using green photocatalysts under visible light including direct sunlight without consuming additional energy.