Role Of H2O2 Research Articles

Direct Sonochemical Leaching of Li, Co, Ni, and Mn from Mixed Li-Ion Batteries with Organic Acids

Metals such as nickel, cobalt, lithium, and manganese are widely used in lithium-ion batteries (LIBs) in electronic devices and electric vehicles. It is forecast that there will be a strong increase in the number of electronic devices and electric vehicles in the coming years. (1) Background: In this paper, the application of ultrasound waves on improving Li, Co, Mn, and Ni leaching efficiency from mixed active cathode materials from different types of LIBs is presented. (2) Methods: Environmentally friendly, low-concentrated (0.75 M) organic acids (oxalic acid, citric acid) and, additionally, sulfuric acid, were used in sonochemical and chemical leaching (stirring process) at a temperature of 60 °C. (3) Results: The results showed significantly higher leaching efficiency of metals with ultrasound-assisted treatment, especially when using organic acids. An average of 50% better leaching results were obtained for Li in oxalic acid (99.6%) and for Co (93.1%) in citric acid during sonochemical leaching. (4) Conclusions: Based on the theory of hydrogen peroxide formation during ultrasound wave transition in solutions, the role of H2O2 as one of the most effective reductants used to enhance cobalt, manganese, and nickel leaching from LIBs is indicated.

Insights into the pH-dependent mechanism of peracetic acid activation by biochar-supported zero-valent iron/cobalt bimetallic nanoparticles: The shift of reactive sites and the dual role of hydrogen peroxide

The peracetic acid (PAA)-based water purification process is often controlled by the solution pH. Herein, we explored the usage of biochar (BC) supported zero-valent iron/cobalt nanoparticles (Fe/Co@BC) for triggering PAA oxidation of sulfamethazine (SMT), and discovered the PAA activation mechanisms at different pHs. Fe/Co@BC exhibited extraordinary PAA activation efficiency over the pH range of 3.0–8.2, effectively broadening the working pH of the zero-valent iron nanoparticles (NZVI)-PAA process. Specifically, the SMT removal efficiency increased by 8.3 times in Fe/Co@BC-PAA system compared to the NZVI-PAA system at pH 8.2. Besides, the leaching and recycling experiments indicated the improved stability and reusability of the materials. For the mechanism study, the main reactive species was •OH under acidic conditions and R-O•/Fe(IV) under neutral/alkaline conditions. More interestingly, the reactive sites on Fe/Co@BC shifted from Fe species to Co species as pH increased, and the role of H2O2 in this reaction system also shifted from a radical precursor to a radical scavenger with increasing pH. This study highlights the distinct mechanism of PAA activation by bimetallic composites under different pH conditions and provides a new efficient approach for PAA activation to degrade organic contaminants.

Insights into the role of H2O2 on corrosion behavior of NiCu low alloy steel in simulated Beishan groundwater

Steel containers used for geological disposal of high-level radioactive waste will be gradually thinned or even perforated due to corrosion, which will lead to radiolysis of nuclides when they contact with infiltrated groundwater and produce H2O2. This work focused on investigating the influence of H2O2 concentration (0%, 0.001%, 0.01%, 0.1% and 1% by volume) on the corrosion behavior of NiCu low alloy steel as the candidate material for containers was comparatively studied by combining corrosion weight loss test, corrosion product analysis, morphology characterization, thermodynamic analysis and electrochemical measurements. As [H2O2] = 0.001%, H2O2 inhibited the formation of γ-FeOOH and enhanced the compactness of rust layer, which effectively blocked the migration of aggressive ions and slowed down the cathodic reduction reaction of rust, thus improving the corrosion resistance of NiCu steel. With the increase of [H2O2] (0.01%→1%), the cathodic process of NiCu steel corrosion was promoted by the increase of dissolved oxygen involved in cathodic depolarization. Meanwhile, the relative content of Fe3O4 in the rust increased, while Fe6(OH)12SO4 and Fe6(OH)12CO3 decreased obviously, which led to the loose and porous rust layer, thus accelerating the corrosion of NiCu steel.

H2O2 promotes trimming-induced tillering by regulating energy supply and redox status in bermudagrass.

Tillering/branching pattern plays a significant role in determining the structure and diversity of grass, and trimming has been found to induce tillering in turfgrass. Recently, it has been reported that hydrogen peroxide (H2O2) regulates axillary bud development. However, the role of H2O2 in trimming-induced tillering in bermudagrass, a kind of turfgrass, remains unclear. Our study unveils the significant impact of trimming on promoting the sprouting and growth of tiller buds in stolon nodes, along with an increase in the number of tillers in the main stem. This effect is accompanied by spatial-temporal changes in cytokinin and sucrose content, as well as relevant gene expression in axillary buds. In addition, the partial trimming of new-born tillers results in an increase in sucrose and starch reserves in their leaves, which can be attributed to the enhanced photosynthesis capacity. Importantly, trimming promotes a rapid H2O2 burst in the leaves of new-born tillers and axillary stolon buds. Furthermore, exogenous application of H2O2 significantly increases the number of tillers after trimming by affecting the expression of cytokinin-related genes, bolstering photosynthesis potential, energy reserves and antioxidant enzyme activity. Taken together, these results indicate that both endogenous production and exogenous addition of H2O2 enhance the inductive effects of trimming on the tillering process in bermudagrass, thus helping boost energy supply and maintain the redox state in newly formed tillers.

Root endophyte-mediated alteration in plant H2O2 homeostasis regulates symbiosis outcome and reshapes the rhizosphere microbiota.

Endophytic symbioses between plants and fungi are a dominant feature of many terrestrial ecosystems, yet little is known about the signaling that defines these symbiotic associations. Hydrogen peroxide (H2O2) is recognized as a key signal mediating the plant adaptive response to both biotic and abiotic stresses. However, the role of H2O2 in plant-fungal symbiosis remains elusive. Using a combination of physiological analysis, plant and fungal deletion mutants, and comparative transcriptomics, we reported that various environmental conditions differentially affect the interaction between Arabidopsis and the root endophyte Phomopsis liquidambaris, and link this process to alterations in H2O2 levels and H2O2 fluxes across root tips. We found that enhanced H2O2 efflux leading to a moderate increase in H2O2 levels at the plant-fungal interface is required for maintaining plant-fungal symbiosis. Disturbance of plant H2O2 homeostasis compromises the symbiotic ability of plant roots. Moreover, the fungus-regulated H2O2 dynamics modulate the rhizosphere microbiome by selectively enriching for the phylum Cyanobacteria, with strong antioxidant defenses. Our results demonstrated that the regulation of H2O2 dynamics at the plant-fungal interface affects the symbiotic outcome in response to external conditions and highlight the importance of the root endophyte in reshaping the rhizosphere microbiota.

Metal-Plastic Hybrid Additive Manufacturing to Realize Small-Scale Self-Propelled Catalytic Engines.

Microengines driven by catalytic decomposition of a fuel have been an interesting research area recently due to their diverse applications, such as environmental monitoring and drug delivery. Literature reports a number of studies on this topic where researchers have made various attempts to manufacture such microengines. Some such methods are deposition of catalytic metal layers on sacrificial photoresists, electrochemical deposition of metal layers on polymeric structures, or 3D printing of structures followed by multi-step loading of structures with catalysts. These methods, even though proven to be effective, are tedious, time-consuming, and expensive. To address these issues, herein we report a 3D printing technique to realize microengines in a simple, rapid, and inexpensive single-step process. The printing of various shapes of microengines is achieved using digital light processing printing of a catalyst resin, where Pd(II) acts as a catalyst resin. The proposed integrated molding process can achieve cost-effective preparation of high-efficiency microengines. We demonstrate the locomotion of these microengines in 30% (w/w) H2O2 through the decomposition of H2O2 to generate oxygen to facilitate the self-propelled locomotion. The study characterizes the microengine based on several factors, such as the role of H2O2, Pd, shape, and design of the microengine, to get a full picture of the self-locomotion of microengines. The study shows that the developed method is feasible to manufacture microengines in a simple, rapid, and inexpensive manner to be suitable for numerous applications such as environmental monitoring, remediation, drug delivery, diagnosis, etc., through the modification of the catalyst resin and fuel, as desired.

Comparative Analysis of Degradation of Pristine Nafion and Catalyst Coated Membrane Subjected to Ex-Situ Fenton's Test Approach

Polyfluorinated sulfonic –acid ionomer membranes (e.g Nafion) are extensively used today as the benchmark materials for the electrolyte membrane in PEM water electrolysis. It is broadly accepted that the state of the health of PFSA membranes are adversely impacted by the chemical degradation occured during operation of PEMWE. The crossover gases on the catalytic surface generate Hydrogen Peroxide which is homolytically or in the presence of ferrous salts produce reactive oxygen species like hydroperoxyl (HO.) and hydroxyl (HO.) radicals. These radicals attack the ionomer subsequently leading to chain scission, unzipping and loss of functional groups and release of HF in the effluent water.Other than Fe3+, several transition metal ions Cu2+, Ni2+, Ti3+, Cu+, can poison the membrane significantly. The fact that membrane degradation is accelerated owing to introduction of ferrous ions is fervently implemented in ex-situ degradation tests (known as Fentons tests) to evaluate the durability of membrane materials.This work depicts a systematic investigation of degradation of pristine Nafion and catalyst coated Nafion membrane using a Fentons accelerated aging experiment. The durability of Nafion 117 and catalyst coated Nafion membrane with various counter ions against H2O2 was explored as a degradation factor of polymer electrolyte water electrolyser. Two distinct variations of the experiments were compared : (1) Nafion and CCM were dipped in only hydrogen peroxide solution, (2) Nafion and CCM were exposed to a solution containing ferrous ions and peroxide. Accelerated aging experiments were conducted over 3-7 days. The difference in degradation phenomena with and without Fe ions were evaluated in terms of the fluoride ion release. For both cases, to quantify the effect of water activity in Nafion and CCM chemical structure on both water diffusion and interfacial transport, pulse field gradient spin echo nuclear magnetic resonance (PFGSE-NMR) technique has been employed. Furthermore the equivalent weight of the Nafion and CCM can vary in presence of aforementioned chemical stressors which can be accurately quantitatively studied by confocal Raman spectroscopy. Morphological characteristic before and after aging test was also investigated. Role of H2O2 and ferous ion in mechanical behaviour of Nafion and CCM were also analyzed. The same experiment was repeated for different transition metal ions. This work sheds light on decomposition mechanism of Nafion and CCM in more detail.

Photodegradation of Methyl violet using Ag modified TiO2 nanotubes by UV and UV/ H2O2

Titanium dioxide (TiO2) is a semiconductor material that is frequently utilized in photodegradation applications. Its application in photodegradation is constrained by its broad band gap of 3.2 eV and increased rate of photoelectron recombination. However, by doping TiO2 with metallic nanoparticles, the band gap can be modified and photodegradation can be improved. The present study explores the fabrication of Ag-modified TiO2 nanotube photocatalysts by electrochemical anodization followed by hydrothermal method. The structural, morphological, compositional, optical, and thermal properties of prepared photocatalysts were characterized by X-ray analysis, Field emission scanning electron microscopy, N2 adsorption desorption analysis, X-ray photoelectron spectroscopy, Energy dispersive X-ray spectroscopy, UV–Vis diffuse reflectance analysis and Thermogravimetric-differential thermal analysis. The prepared photocatalyst was utilized to investigate the degradation of methyl violet in the presence of UVA and UVC radiation. The effects of UVA and UVC illumination on the degradation process, the effect of Ag loading in the TiO2 nanotube arrays and the role of H2O2 in the degradation of pollutant were studied. The degradation efficiency of methyl violet in the presence of UVC light was three times that of UVA light. For pristine TiO2 photocatalyst, the maximum degradation of 70% was obtained under UVC illumination in 8 h. When H2O2 was added, complete degradation was observed within 3 h. Reusability studies have shown that photocatalysts are stable and can be used for the degradation of methyl violet.

Efficient wastewater treatment through nano-catalyst: The role of H2O2 and application in wide pH window

Efficient wastewater treatment through nano-catalyst: The role of H2O2 and application in wide pH window

Formation, Reactivity, and Catalytic Behavior of a Keggin Polyoxometalate/Bipyridine Hybrid in the Epoxidation of Cyclooctene with H2O2.

The present study further explores the behavior of polyoxometalate-based hybrid compounds as catalysts for liquid-phase cyclooctene epoxidation with H2O2. Precisely, it unveils the nature of the relevant active species derived from the hybrid based on Keggin polyoxometalate (POM) and bipyridines (bpy) of formula (2,2'-Hbpy)3[PW12O40] (1). Whereas (i) it is generally accepted that the catalytic oxidation of organic substrates by H2O2 involving Keggin HPAs proceeds via an oxygen transfer route from a peroxo intermediate and (ii) the catalytically active peroxo species is commonly postulated to be the polyperoxotungstate {PO4[W(O)(O2)2]4}3- complex (PW4), we show that the studied epoxidation reaction seems to be more sophisticated than commonly reported. During the catalytic epoxidation, 1 underwent a partial transformation into two oxidized species, 2 and 3. Compound 3 corresponding to 2,2'-bipyridinium oxodiperoxotungstate of formula [WO(O2)2(2,2'-bpy)] was shown to be the main species responsible for the selective epoxidation of cyclooctene since 2 (in which the POM is associated with a protonated mono-N-oxide derivative of 2,2'-bpy of formula (2,2'-HbpyO)3[PW12O40]) exhibited no activity. The structures of 1, 2, and 3 were solved by single-crystal X-ray diffraction and were independently synthesized. The speciation of 1 was monitored under catalytic conditions by 1H and 1H DOSY NMR spectroscopies, where the formation in situ of 2 and 3 was revealed. A reaction mechanism is proposed that highlights the pivotal, yet often underestimated, role of H2O2 in the reached catalytic performances. The active species responsible for the oxygen transfer to cyclooctene is a hydroperoxide intermediate species that is formed by the interaction between the anionic structure of the catalyst and H2O2. The latter operates as a "conservative agent" whose presence in the catalytic system is required to prevent the catalysts from deactivating irreversibly.

From liver fibrosis to hepatocarcinogenesis: Role of excessive liver H2O2 and targeting nanotherapeutics.

Liver fibrosis and hepatocellular carcinoma (HCC) have been worldwide threats nowadays. Liver fibrosis is reversible in early stages but will develop precancerosis of HCC in cirrhotic stage. In pathological liver, excessive H2O2 is generated and accumulated, which impacts the functionality of hepatocytes, Kupffer cells (KCs) and hepatic stellate cells (HSCs), leading to genesis of fibrosis and HCC. H2O2 accumulation is associated with overproduction of superoxide anion (O2 •-) and abolished antioxidant enzyme systems. Plenty of therapeutics focused on H2O2 have shown satisfactory effects against liver fibrosis or HCC in different ways. This review summarized the reasons of liver H2O2 accumulation, and the role of H2O2 in genesis of liver fibrosis and HCC. Additionally, nanotherapeutics targeting H2O2 were summarized for further consideration of antifibrotic or antitumor therapy.

Electrochemical degradation of 10,11-dihydro-10-hydroxy carbamazepine as the main metabolite of carbamazepine.

10,11-Dihydro-10-hydroxy carbamazepine has been degraded in deionized water and wastewater samples using an electrochemical process. The anode used in the treatment process was graphite-PVC. Different factors such as initial concentration, NaCl amount, type of matrix, applied voltage, role of H2O2, and pH solution were investigated in the treatment of 10,11-dihydro-10-hydroxy carbamazepine. From the outcome of the results, it was noticed that the chemical oxidation of the compound followed a pseudo-first-order reaction. The rate constants were ranged between 22 × 10-4 and 483 × 10-4min-1. After electrochemical degradation of the compound, several by-products were raised, and they were analyzed using an accurate instrument, liquid chromatography-time of flight-mass spectrometry (LC-TOF/MS). In the present study, the treatment of the compound was followed by high energy consumption under 10V and 0.5g NaCl, reaching up to 0.65 Wh mg-1 after 50min. The inhibition of E. coli bacteria after incubation of the treated 10,11-dihydro-10-hydroxy carbamazepine sample was investigated in terms of toxicity.

Design of a label-free aptasensor for electrochemical determination of hemoglobin: investigation of the peroxidase-like activity of hemoglobin for the sensing of different substrates.

The unbalanced hemoglobin level in biological fluids can cause several diseases; hence it can be used as a biomarker for diagnosis. We aim, in the present study, to construct a label-free electrochemical aptasensor for the quantification of hemoglobin. For that, a conjugate of L-cysteine and gold nanoparticles was used for the aptamer immobilization on screen printed carbon electrodes. Using square wave voltammetry, the calibration plot was obtained and it was linear in the range of 50 ng ml-1 to 36 000 ng ml-1 while the detection limit was 1.2 ng ml-1. After the binding of Hb on the modified screen-printed carbon electrode surface, the peroxidase-like activity of the bound hemoglobin was explored in the quantification of different substrates. Hydrogen peroxide and nitrite were chosen as model analytes. Amperometric measurements showed wide linear ranges: 0.2 μM-7.7 mM and 3.6 nM-1.3 mM for H2O2 and nitrite, respectively, with detection limits of 0.044 μM and 0.55 nM. In the proposed strategy, the aptamer provides excellent orientation and a biocompatible environment for hemoglobin whose catalytic activity plays a key role in H2O2 and nitrite analysis.

The role of peroxiredoxins PrxA and PrxB in the antioxidant response, carbon utilization and development in Aspergillus nidulans

In addition to their role in the breakdown of H2O2, some peroxiredoxins (Prxs) have chaperone and H2O2 sensing functions. Acting as an H2O2 sensor, Prx Gpx3 transfers the oxidant signal to the transcription factor Yap1, involved in the antioxidant response in Saccharomyces cerevisiae. We have shown that Aspergillus nidulans Yap1 ortholog NapA is necessary for the antioxidant response, the utilization of arabinose, fructose and ethanol, and for proper development. To address the Prx roles in these processes, we generated and characterized mutants lacking peroxiredoxins PrxA, PrxB, PrxC, or TpxC. Our results show that the elimination of peroxiredoxins PrxC or TpxC does not produce any distinguishable phenotype. In contrast, the elimination of atypical 2-cysteine peroxiredoxins PrxA and PrxB produce different mutant phenotypes. ΔprxA, ΔnapA and ΔprxA ΔnapA mutants are equally sensitive to H2O2 and menadione, while PrxB is dispensable for this. However, the sensitivity of ΔprxA and ΔprxA ΔnapA mutants is increased by the lack of PrxB. Moreover, PrxB is required for arabinose and ethanol utilization and fruiting body cell wall pigmentation. PrxA expression is partially independent of NapA, and the replacement of peroxidatic cysteine 61 by serine (C61S) is enough to cause oxidative stress sensitivity and prevent NapA nuclear accumulation in response to H2O2, indicating its critical role in H2O2 sensing. Our results show that despite their high similarity, PrxA and PrxB play differential roles in Aspergillus nidulans antioxidant response, carbon utilization and development.

The sperm chromatin structure assay does not detect alterations in sperm chromatin structure induced by hydrogen peroxide

The objective of this study was to investigate the effects of hydrogen peroxide (H2O2) on the chromatin structure of sperm. For this purpose, 44 cryopreserved bovine ejaculates were analyzed immediately post-thaw (control sperm, CON S), after 1 h of post-thaw incubation (non-oxidized sperm, NOX S), and after 1 h of post-thaw incubation in different concentrations of H2O2 (OX S; 50, 100 µM, 1000 µM H2O2). Sperm motility was determined using computer-assisted sperm analysis. Sperm plasma membrane and acrosome integrity were assessed by flow cytometry after staining with propidium iodide and fluorescein isothiocyanate-conjugated peanut agglutinin. Chromatin damage was assessed using the sperm chromatin structure assay (SCSA), and DNA damage was evaluated using the single cell gel electrophoresis (Comet) assay. Sperm motility and plasma membrane and acrosome integrity decreased while chromatin damage and DNA damage increased after 1 h of incubation (P < 0.05). The addition of H2O2 adversely affected all parameters (P < 0.05) except for chromatin structure. The role of H2O2 in sperm chromatin damage was investigated by supplementation of 10 IU catalase, which reversed the damage (P < 0.05). Interestingly, the chromatin decondensation induced by 10 mM dithioreitol, evidenced by an increase in chromatin damage in the SCSA (P < 0.05), was reversed by H2O2. In conclusion, H2O2 causes alterations in sperm functional status and DNA integrity. However, our results show that high concentrations of H2O2 can induce chromatin condensation, and thus the use of the SCSA for the assessment of H2O2-induced chromatin damage should be carefully considered.

Chemistry of Hydrogen Peroxide Formation and Elimination in Mammalian Cells, and Its Role in Various Pathologies

Hydrogen peroxide (H2O2) is a compound involved in some mammalian reactions and processes. It modulates and signals the redox metabolism of cells by acting as a messenger together with hydrogen sulfide (H2S) and the nitric oxide radical (•NO), activating specific oxidations that determine the metabolic response. The reaction triggered determines cell survival or apoptosis, depending on which downstream metabolic pathways are activated. There are several ways to produce H2O2 in cells, and cellular systems tightly control its concentration. At the cellular level, the accumulation of hydrogen peroxide can trigger inflammation and even apoptosis, and when its concentration in the blood reaches toxic levels, it can lead to bioenergetic failure. This review summarizes existing research from a chemical perspective on the role of H2O2 in various enzymatic pathways and how this biochemistry leads to physiological or pathological responses.

Kinetic isotope effects in H2O2 self-decomposition: Implications for triple oxygen isotope systematics of secondary minerals in the solar system

Hydrogen peroxide (H2O2) is a ubiquitous molecule in nature that shapes the redox state of planetary surfaces. Given that H2O2 is a major oxidant, isotope effects associated with H2O2 chemistry play a key role in determining triple oxygen isotopic compositions (δ17O and δ18O) of secondary aerosols and minerals, which are powerful proxies for understanding terrestrial/Martian atmospheric chemistry, and chemical evolution in the solar nebular. However, isotope effects in H2O2 self-decomposition processes, which actively occur in nature due to the thermal instability of H2O2, remains poorly understood. Here, we report a hitherto overlooked large and mass-dependent isotope fractionation in aqueous H2O2 self-decomposition processes quantified in a series of kinetic experiments. δ18O in remaining H2O2 is several tens of per mil (‰) with respective to initial H2O2. By synthesizing triple oxygen isotope measurements of natural H2O2, ozone, various oxyanions formed in the atmosphere (sulfate, nitrate, perchlorate, and carbonate), and oxygen-bearing secondary minerals in meteorites, we find that a decoupled Δ17O–δ18O pattern in natural H2O2 is attributed in part to the high degree of mass-dependent δ18O variation in H2O2 decomposition, and further argue that this unique signature may play a crucial role in triple oxygen isotope systematics in a board spectrum of secondary minerals in our solar system including aerosols, sediments, and meteorites. Our results shed fresh insights into recent debates on the role of H2O2 in the formation of these secondary minerals in the modern Earth, geological past, and other planets. The isotope effect experimentally quantified in this study are needed for future improvements of planetary atmosphere and solar nebular evolution models. We highlight the importance of further experimental and theoretical efforts to quantify isotope effects in H2O2 chemistry that are representative of natural systems.

ClNOX1/ClNOXR-mediated MAPK and cAMP-PKA signalling pathways and ROS metabolism are involved in Curvularia lunata sexual reproduction and host infection.

NADPH oxidases (NOXs) and hydrogen peroxide (H2 O2 ) are involved in physiological and pathological processes, and cell fate decisions in organisms. However, regulatory mechanism of NOXs and the role of H2 O2 on fungal sexual reproduction and host infection remain largely unexplored. Here, we identified ROS metabolic genes and key signalling genes of MAPK and cAMP-PKA pathways in Curvularia lunata, which were NOX ClNOX1 and ClNOXR, superoxide dismutase ClSOD1 and catalase ClCAT4, redox-regulated transcription factor ClAP1, Ras small GTPases Clg2P, pheromone-response MAPK ClK1 and cAMP-PKA ClSCHA, and characterized the functions of these genes. The results showed that ClNOX1 localized to the plasma membrane. ClNOX1 and ClNOXR were involved in sexual reproduction and host infection via ClNOX1/ClNOXR-derived H2 O2 as well as MAPK and cAMP-PKA signalling pathways. H2 O2 acted as a signalling molecule to regulate sexual reproduction and host infection in C. lunata.

GR24-mediated enhancement of salt tolerance and roles of H2O2 and Ca2+ in regulating this enhancement in cucumber

This study investigated the regulation of the exogenous strigolactone (SL) analog GR24 in enhancing the salt tolerance and the effects of calcium ion (Ca2+) and hydrogen peroxide (H2O2) on GR24's regulation effects in cucumber. The seedlings were sprayed with (1) distilled water (CK), (2) NaCl, (3) GR24, then NaCl, (4) GR24, then H2O2 scavenger, then NaCl, and (5) GR24, then Ca2+ blocker, then NaCl. The second true leaf was selected for biochemical assays. Under the salt stress, the exogenous GR24 maintained the ion balance, increased the activity of antioxidant enzymes, reduced the membrane lipid peroxidation, and increased the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), accompanied by a decrease in relative conductivity, an increase in the proline content, and elevated gene expression levels of antioxidant enzymes, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, calcium-dependent protein kinases (CDPKs), salt overly sensitive SOS1, CBL-interacting protein kinase 2 (CIPK2), and calcineurin B-like protein 3 (CBL3). Such protective effects triggered by GR24 were attenuated or almost abolished by ethylene glycol tetraacetic acid (EGTA), lanthanum chloride (LaCl3, Ca2+ channel blocker), diphenyleneiodonium (DPI, NADPH oxidase inhibitor), and dimethylthiourea (DMTU, hydroxyl radical scavenger). Our data suggest that exogenous GR24 is highly effective in alleviating salt-induced damages via modulating antioxidant capabilities and improving ionic homeostasis and osmotic balance and that H2O2 and Ca2+ are required for GR24-mediated enhancement of salt tolerance.

ROS‐responsive thioether‐containing hyperbranched polymer micelles for light‐triggered drug release

AbstractAs a kind of promising drug carriers, smart polymers have attracted much attention due to the effective and controlled drug release in target cells. Herein, a reactive oxygen species (ROS)‐responsive thioether‐containing amphiphilic hyperbranched polymer prepared from MTPA and TMPTGE (HBPMT) is synthesized from 3‐(methylthio)propylamine (MTPA) and trimethylolpropane triglycidyl ether (TMPTGE) by the amine‐epoxy click reaction via A2 + B3 one‐pot approach. Benefiting from its inherent amphiphilic nature, HBPMT can self‐assemble into stable micelles in water. Triggered by H2O2, these micelles can be dissociated rapidly because hydrophobic thioether segments in their cores are oxidized into hydrophilic sulfoxide or sulfone groups. Additionally, the ROS produced by photosensitizer under light irradiation can also play the same role of H2O2. Such HBPMT micelles can be utilized to encapsulate anticancer drug paclitaxel (PTX) and photosensitizer chlorin e6 (Ce6) simultaneously for drug delivery and control release. The methyl thiazolyl tetrazolium assay toward MCF‐7 tumor cells (a human breast adenocarcinoma cell line) indicates that these micelles encapsulated with PTX and Ce6 exhibit a significant combinational efficacy of cell proliferation inhibition, which means the promising potential for synergistic chemo‐photodynamic cancer therapy. Such a novel nanocarrier based on amphiphilic to hydrophilic transition would provide a candidate for controlled drug release and cancer combination therapy.