Increasing H2O2 Concentration Research Articles

The removal of NO from flue gas by NaOH-catalyzed H2O2 system: Mechanism exploration and primary experiment

Currently, most advanced oxidation denitrification technologies require long flue gas residence time to obtain ideal NO removal efficiency. The NaOH-catalyzed H2O2 system proposed in this paper can obtain 98% NO removal efficiency under the condition of flue gas residence time of 3 s. The mechanism of NO removal and H2O2 decomposition to O2 were proposed. It was confirmed with ESR (Electron-spin-resonance), inhibitor experiments and UV-Vis spectrophotometer that the main group in the reaction process was·O2- radicals, which reacted with NO to form ONOO-, and ONOO- would be gradually transformed into NO3- and NO2- in the air. The effect of some primary factors on the NO removal efficiency and the percentage of H2O2 decomposition to O2 were also investigated. The increase of initial pH has a positive effect on NO removal, while the promotion of NO removal by increasing H2O2 concentration and reaction temperature is limited and the increase of NO has a negative effect on NO removal. Initial pH has a dual impact on the percentage of H2O2 decomposition to O2, H2O2 concentration and reaction temperature promote the decomposition of H2O2 to O2, while NO concentration has an inhibiting effect on it.

Simulated microgravity contributed to modification of callogenesis performance and secondary metabolite production in CannabisIndica

In vitro plant culture paves the way for meeting the industrial demand of pharmaceutically valuable secondary metabolites. This study intends to monitor how callus cells of Cannabis indica respond to the simulated microgravity (clinorotation; a Man-made technology). Callus initiation resulted from the culture of the leaf explant in a medium supplemented with kinetin (0.5 mgL−1) and 2, 4-D (2 mgL−1). Calli were treated with microgravity at three exposure times (0, 3, and 5 days). The microgravity treatments increased callus biomass about 2.5-fold. The clinorotation treatments transcriptionally induced the olivetolic acid cyclase (OAC) and olivetol synthase (OLS) genes about 6.2-fold. The tetrahydrocannabinolic acid synthase (THCAS) and cannabidiolic acid synthase (CBDAS) genes displayed a similar upward trend in response to microgravity. The applied treatments also stimulated the expression of the ethylene-responsive element-binding proteins (ERF1B) and WRKY1 transcription factors by an average of 7.6-fold. Moreover, the simulated microgravity triggered epigenetic modification in the DNA methylation profile. The HPLC-based assessment validated the high efficacy of the clinorotation treatments to increase the concentration of cannabinoids, including Cannabigerol (CBG) and Cannabidiol (CBD). However, the clinorotated calli contained a lower concentration of Tetrahydrocannabinol (THC) than the control group. The microgravity treatments increased concentrations of proline (79%), soluble sugars (61.3%), and proteins (21.4%) in calli. The biochemical assessment revealed that the clinorotation treatments slightly increased H2O2 concentration. The upregulation in the activities of peroxidase, catalase, and phenylalanine ammonia-lyase enzymes resulted from the microgravity treatments. Both HPLC and molecular assessments validated the significant efficacy of microgravity to enhance the production of cannabinoids.

The role and mechanisms of the two-component system EnvZ/OmpR on the intracellular survival of Aeromonas hydrophila.

Aeromonas hydrophila infections are common in aquaculture. Our previous studies found that the A.hydrophila B11 strain can survive in fish macrophages for at least 24 h and the two-component system EnvZ/OmpR may be involved in intracellular survival. To reveal the role and mechanism of the two-component system EnvZ/OmpR in intracellular survival of A.hydrophila, the genes of envZ/ompR were silenced by shRNAi. The results showed that the survival rates of the envZ-RNAi and ompR-RNAi strains were only 2.05% and 3.75%, respectively, which were decreased by 91% and 83.6% compared with that of the wild-type strain. The escape ability of envZ-RNAi and ompR-RNAi was also decreased by 51.4% and 19.7%, respectively. The comparative transcriptome analysis revealed that the functional genes directly related to bacterial intracellular survival mainly included the genes related to anti-stress capacity, and the genes related to Zn2+ and Mg2+ transport. Further research confirmed that two-component system EnvZ/OmpR can regulate the expression of the important molecular chaperones, such as groEL, htpG, dnaK, clpB and grpE. The expression of these molecular chaperones in wild-type strain was up-regulated with the increase in H2 O2 concentrations, while the expression of these molecular chaperones in silent strains did not change significantly. Cells that phagocytosed wild-type strain had higher ROS content than cells that phagocytosed silent strains. Two-component system EnvZ/OmpR could also regulate zinc transporter (znuA, znuB, znuC) and zinc efflux protein (zntA) to maintain zinc homeostasis in cells, thus affecting the ability of bacteria to survive in phagocytes. Moreover, two-component system EnvZ/OmpR could affect the growth and intracellular survival of A.hydrophila by regulating the expression of MgtA, MgtC and MgtE and participating in bacterial Mg2+ homeostasis in fish macrophages.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

Performance and degradation pathways of bromuconazole by gamma radiation in aqueous solutions

Gamma irradiation has received increasing attention due to its high potential in the degradation of recalcitrant pollutants. Thus, in the present study, gamma irradiation was used for the degradation of bromuconazole with the presence of hydrogen peroxide (H2O2) as a source of •OH and humic acid as natural organic matter. The effects of initial concentration, irradiation doses and pH were examined. A kinetic study was performed, and the by-products were identified by HPLC-QTOF-MS/MS. Results showed that the degradation process of bromuconazole was pseudo-first-order and 99.9% of bromuconazole was decomposed under an absorbed dose of 1 kGy. The percentage of removal increased with doses and the degradation process was accelerated under neutral conditions. The addition of H2O2 showed a synergistic effect on the decomposition of bromuconazole and the degradation efficiency increased with the increase of H2O2 concentration. Humic acid indicated a negative influence on the degradation efficiency, which decreased from 99.6% to 70.365% at a dose of 0.8 kGy when the humic acid concentration was 20 mg/L. Six degradation products were identified and the kinetic rates of three intermediate compounds were calculated using a Himmelblau-Jones-Bischoff numerical analysis technique. A study conducted by 1H NMR indicated a complete mineralization at 1.2 kGy.

Ready-to-use optical H2O2 sensor based on stimuli-responsive polyacrylic film and nanofibers containing spiropyran

Nowadays, design of conventional and efficient optical H2O2 sensors would be of great importance due to their lower cost and ease of follow-up, compared to the other widely used techniques such as electrochemical or chromatographic methods. Here, stimuli-responsive sensors containing photochromic (R/S)-2-(3′,3′-dimethyl-6-nitro-3′H-spiro[chromene-2,2′-indole]-1′-yl) ethanol (SPOH) and acrylic terpolymer film or nanofibers were prepared for H2O2 detection through a reaction-induced and concentration-dependent process. The polymer phase acts as an efficient substrate for exploitation of such sensors in aqueous media. Poly(methyl methacrylate-butyl acrylate-hydroxyethyl methacrylate) (MBH) was prepared via miniemulsion polymerization and its chemical structure was characterized by FTIR and 1H NMR spectroscopies. Then, it was doped with SPOH and the corresponding film (MBH/SPOH@F) and nanofibers (MBH/SPOH@NF) were fabricated via spin-coating and electrospinning techniques, respectively, and their morphologies were investigated by SEM. Colorimetric analyses were employed to evaluate performance of the obtained samples toward H2O2 after sensitization by UV irradiation. Both samples demonstrated visual color changes together with decrement in maximum absorption wavelengths with the increase in H2O2 concentration. Limit of detection (LOD) for MBH/SPOH@F and MBH/SPOH@NF were calculated to be 11 and 2.3 mg/dL, respectively. Moreover, MBH/SPOH@NF showed faster response (50 min) with respect to MBH/SPOH@F (60 min). Enhanced sensitivity of MBH/SPOH@NF comes from higher specific surface area and porosity of the nanofibers compared to the corresponding film. This led to more accessibility of H2O2 to SPOH molecules in the detection process. Finally, practical application of the ready-to-used and solid sensor was validated with the recovery of 94–97% in water resources.

Overexpression of OHPs in Neopyropia yezoensis (Rhodophyta) reveals their possible physiological roles

The red macroalga Neopyropia yezoensis is a model organism, and an economically important seaweed widely cultured in eastern Asian countries. Transgenic research on N. yezoensis is difficult and limited to reporter genes and selection markers due to the specificities of this species. In this study, plasmids were constructed to overexpress six one helix protein (OHP) coding genes in N. yezoensis, and four transgenic lines with high expression levels of the target genes were obtained. The photosynthetic parameters were determined and it was found that the overexpression of OHPs altered electron transport in photosystem I and photosystem II, which was indicated by the increased 1-qL values and decreased P700+ reduction rates. The results also showed that the non-photochemical quenching (NPQ) kinetics in N. yezoensis could not be stimulated by high light (HL) treatment. Two of the four transgenic lines showed stimulated NPQ, and they did not exhibit an obvious increased ability to resist to HL, which was shown by the decreased Fv/Fm values. The increased H2O2 content and decreased peroxidase (POD) activity were considered the possible results of the overexpressed OHPs, and they were responsible for the enhanced NPQ and HL sensitivity in those two transgenic lines.

Cloning and expressions of chop in loach (Misgurnus anguillicaudatus) and its response to hydrogen peroxide (H2O2) stress.

C/EBP [CCAAT/enhancer-binding protein]-homologous protein gene (chop) which plays an important role in endoplasmic reticulum stress-induced apoptosis was investigated here by RACE and qPCR in an aquaculture animal for the first time. The full-length cDNA sequence of loach (Misgurnus anguillicaudatus) chop was 2533 bp, encoding 266 amino acids. The expression level of loach chop changed during different early life stages, with the highest expression at the 8-cell stage. Among different tissues, loach chop predominantly was expressed in gill, spleen, and gonad. We performed a hydrogen peroxide (H2O2, a common-used disinfectant) stress trial to explore the role of loach chop, with three different concentrations (0 μM, 50 μM, and 100 μM) of H2O2. The 100-μM dose was lethal for half the population but the other concentrations did not result in mortality. The activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX) in loach gill, liver, and spleen decreased with extended stress time and increased H2O2 concentration. The expression levels of gill chop in loaches from the 100-μM group were significantly higher than those from the other two treatment groups at 12 and 24 h of exposure. atf4 and bax, two proapoptotic genes, were significantly upregulated in gills of loaches from the 100-μM group compared to the other two groups 18 h and 24 h after treatment. bcl2, an antiapoptotic gene, presented an opposite trend. These results indicated a close relationship between H2O2 stress and fish apoptosis with loach chop playing an important role in H2O2 stress response.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10695-022-01067-3.

Emulsification of waste cooking oil biodiesel blend with hydrogen peroxide to assess tailpipe emissions and performance of a compression ignition engine

AbstractHydrogen peroxide (H2O2) is an excellent oxidant carrier that finds its use in combustion and fuel applications. In the present study, H2O2 (30% assay) is used as an emulsifier in waste cooking oil biodiesel blend (B20) and the emissions and performance in a compression ignition engine are assessed. Along with the neat B20, three blends of B20 with 0.5%, 1%, and 1.5% H2O2 concentrations are used. Increasing the concentration of H2O2 beyond 1.5% resulted in vapor lock in the fuel pump leading to a loss in injection pressure. An increase in the exhaust gas temperature was recorded with the increase in H2O2 concentration due to improved fuel properties, like, cetane number, thermal conductivity, and microexplosions of fuel droplets. However, NOx emissions decreased mainly due to the presence of the hydroperoxyl group from H2O2. Analysis of variance was also carried out to assess the statistical significance of H2O2 on the responses and is seen that the maximum impact of H2O2 was positively influencing brake thermal efficiency (BTE), brake‐specific fuel consumption (BSFC), hydrocarbon (HC), and NOx. Compared with the B20 blend, H2O2 emulsified fuel with a concentration of 1.5% showed a substantial reduction of 53.7%, 28.6%, 14.2%, and 16.2% in the average emissions of CO, HC, smoke, and NOx, respectively. Similarly, 7.9% and 7.1% improvement in the BTE and BSFC is obtained. However, more studies are required to ascertain the NOx reduction mechanism and address issues of fuel vaporization at higher concentrations of H2O2.

Structural Variation of Precipitates Formed by Fe(II) Oxidation and Impact on the Retention of Phosphate.

The oxidation-precipitation process of Fe(II) is ubiquitous in the environment and critically affects the fate of contaminants and nutrients in natural systems where Fe(II) is present. Here, we explored the effect of H2O2 concentration on the structure of precipitates formed by Fe(II) oxidation and compared the precipitates to those formed by Fe(III) hydrolysis. Additionally, the phosphate retention under different H2O2 concentrations was evaluated. XRD, TEM, PDA, XPS, and UV-visible absorbance spectroscopy were used to characterize the structure of the formed precipitates; UV-visible absorbance spectroscopy was also used to determine the residual phosphate and Fe(II) in solution. It was found that the predominant precipitates in Fe(II) solution changed from planar-shaped crystalline lepidocrocite (γ-FeOOH) to poor short-range order (poorly crystalline) spherical-shaped hydrous ferric oxide (HFO) with increasing H2O2 concentrations. Although the HFO precipitates formed from Fe(II) resembled those formed from Fe(III) hydrolysis, the former was larger and had clearer lattice fringes. During the formation of γ-FeOOH, both Fe(II)-Fe(III) complexes and ligand-to-metal charge transfer processes were observed, and it was found that Fe(II) was present in the planar-shaped precipitates. Fe(II) might be present in the interior of precipitates as Fe(OH)2, which could serve as a nucleus for the epitaxial growth of γ-FeOOH. In addition, the extent of phosphate retention increased with the H2O2 concentration, indicating the increased reactivity of formed precipitates with H2O2 concentration. More phosphate was retained via coprecipitation with Fe than adsorption on the preformed Fe precipitates due to the incorporation of phosphate within the structure of the formed Fe hydroxyphosphate via coprecipitation.

Performance and emissions of biodiesel engine with hydrogen peroxide emulsification and cerium oxide (CeO2) nanoparticle additives

The use of biodiesel in a compression ignition (CI) engine has shown to be a promising alternative to conventional diesel owing to its ability to substantially reduce carbon and hydrocarbon emissions. However, an increase in the NOx due to the additional oxygen content from the fuel has led to different fuel pretreatment and exhaust gas after-treatment methods to curb emissions. Hydrogen peroxide (H2O2) has been recently investigated as an oxidant and emulsifier in biodiesel blends for CI engines. Although combustion improvement leading to reduced HC and CO emissions are reported, contrasting findings are found in the literature on the effect of NOx. Similarly, CeO2 nanoparticles have demonstrated its capability in NOx abatement and hence this paper aims to assess the combined effect of H2O2 concentration and CeO2 nanoparticles on the performance and exhaust emissions using B20 fuel. Three different concentrations of H2O2 (0.5%, 1%, and 1.5%) along with two levels of CeO2 nanoparticle concentrations (40, 80 ppm) are investigated. Maximum brake thermal efficiency (BTE) is observed at 75% load and 1.5% H2O2 concentration with an average improvement of 1.2% in BTE over neat B20. The average reduction in CO and HC emissions for 1.5% H2O2 emulsification over neat B20 is 56–60% and 41–48% respectively. For the H2O2 concentration of 0.5%, 1%, and 1.5%, the average decrease in NOx compared to B20 fuel is 5.6%, 16.1%, and 22.7% respectively. Increasing the nanoparticle concentration from 40 ppm to 80 ppm also decreases emissions and improves BTE but its impact is significantly lower compared to the effect of H2O2 emulsification. Increasing H2O2 concentration in fuel blend improves the micro explosions leading to better mixing of fuel and air promoting better combustion. This resulted in the reduction of CO, HC, and NOx emissions as H2O2 is an active carrier of O2 and •OH radicals which has a more dominant effect in improving combustion and reducing emissions.

Rapid photosynthetic and physiological response of 2,4-D–resistant Sumatran fleabane (Conyza sumatrensis) to 2,4-D as a survival strategy

AbstractIn this work, we evaluated the short time-induced oxidative stress–mediated rapid metabolic and physiological responses of resistant and susceptible Sumatran fleabane [Conyza sumatrensis (Retz.) E. Walker; syn.: Erigeron sumatrensis Retz.] to 2,4-D herbicide. Under fixed conditions (25 C and 65 ± 5% relative humidity), we assayed injury symptoms, chlorophyll a fluorescence, and antioxidative systems of biotypes both resistant and susceptible to 2,4-D (1,005 g ae ha−1). Under 15 versus 25 C temperatures and light and dark conditions, oxidative stress–mediated damage was assayed on plants that received 2,4-D herbicide applications. The injury symptoms observed in the 2,4-D–resistant biotype were rapid necrosis in leaves within 30 min, with the reestablishment of normal growth within 1 to 2 wk after 2,4-D treatment. The basal antioxidant enzyme activities of superoxide dismutase, catalase, and ascorbate peroxidase were greater in the resistant than in the susceptible biotype, although the activities of all enzymes generally did not differ between untreated and treated in the resistant biotype. The resistant biotype showed great reduction (at 1 and 4 h after application) in the photosynthetic electron transport chain performance index, while these metabolic changes were only detected after 4 h in the susceptible biotype. The resistant biotype recovered from the foliar damage 1 to 2 wk after 2,4-D application, while the susceptible biotype was controlled. The production of H2O2 was responsive to temperature and increased more rapidly in the 2,4-D–resistant biotype than in the susceptible one at both 15 and 25 C; however, there was a greater increase at 25 C in the resistant biotype. H2O2 production was not light dependent in 2,4-D–resistant C. sumatrensis, with increases even under dark conditions. The 2,4-D–resistant biotype showed rapid photosynthetic damage, possibly due to the rapid necrosis and leaf disruption, and increased H2O2 content compared with the susceptible biotype.

Boosting Polyamines to Enhance Shoot Regeneration in Potato (Solanum tuberosum L.) Using AgNO3

Advancements in shoot regeneration systems support biotechnology-based tools used in the genetic improvement of plant crops. This study aims to enhance shoot regeneration in potatoes by boosting polyamine content by adding AgNO3 to the shoot regeneration medium (MS medium supplemented with 30 g L−1 sucrose, 100 mg L−1 myoinositol, and 2.25 BA mg L−1). Five concentrations of AgNO3 (2, 4, 6, 8, and 10 mg L−1) were used in addition to a control. The effect of AgNO3 on regeneration assumed a more or less concentration-dependent bell-shaped curve peaking at 4 mg L−1. Enhancements in shoot regeneration were attributed to the known role of AgNO3 as an ethylene action blocker in addition to improvements in polyamine accumulation without an increase in H2O2 content, lipid peroxidation, or DNA damage. The uncoupling of shoot regeneration and polyamine content recorded at high AgNO3 concentrations can be attributed to the consumption of polyamines to counteract the synchronized oxidative stress manifested by increases in H2O2 content, lipid peroxidation, and DNA damage.

Effects of Cathepsins on Gel Strength and Water-Holding Capacity of Myofibrillar Protein Gels from Bighead Carp (Aristichthys nobilis) under a Hydroxyl Radical-Generation Oxidizing System.

This study investigates the effects of cathepsins on the gel strength and water-holding capacity (WHC) of myofibrillar protein gels from bighead carp (Aristichthys nobilis) under a hydroxyl radical-generation oxidizing system. The myofibrillar proteins were divided into control group (with cathepsins) and E64 group (without cathepsins). The changes of cathepsin B and cathepsin L activities, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), protein oxidation (total sulfhydryl and carbonyl contents), and chemical interactions (nonspecific association, ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfides) of myofibrillar protein and gels, as well as the gel strength and WHC of two groups under 0–100 mM H2O2, were measured. The results indicated that mild oxidation (10 mM H2O2) made a better gel strength and WHC. Cathepsin B and L activities decreased with increasing H2O2 concentrations but their effects on myofibrillar protein degradation still existed during 0.1–50 mM H2O2, which was expressed by higher carbonyl contents and ionic bonds at 0.1 and 50 mM H2O2, higher total sulfhydryl contents at 0 mM H2O2, and a lower intensity of MHC and actin of the control group than the E64 group. Besides more protein degradation, cathepsin proteolysis also resulted in lower gel strength and WHC in control gels than E64 gels under mild oxidation, which could be explained by lower hydrophobic interaction and moderate disulfides bonds between gel protein molecules of control gels.

Salt induced oxidative stress alters physiological, biochemical and metabolomic responses of green microalga Chlamydomonas reinhardtii

Salinity is one of the most significant environmental factors limiting microalgal biomass productivity. In the present study, the model microalga Chlamydomonas reinhardtii (C. reinhardtii) was exposed to 200 mM NaCl for eight days to explore the physiological, biochemical and metabolomic changes. C. reinhradtii exhibited a significant decrease in growth rate, and Chl a and Chl b levels. 200 mM NaCl induced ROS generation in C. reinhardtii with increase in H2O2 content. This caused lipid peroxidation with increase in MDA levels. C. reinhardtii also exhibited an increase in carbohydrate and lipid accumulation under 200 mM NaCl conditions as storage molecules in cells to maintain microalgal survival. In addition, NaCl stress increased the content of carotenoids, polyphenols and osmoprotectant molecules such as proline. SOD and APX activities decreased, while ROS-scavenger enzymes (POD and CAT) decreased. Metabolomic response showed an accumulation of the major molecules implicated in membrane remodelling and stress resistance such oleic acid (40.29%), linolenic acid (19.29%), alkanes, alkenes and phytosterols. The present study indicates the physiological, biochemical and metabolomic responses of C. reinhardtii to salt stress.

Silver nanosol SERS/Flu/Abs trimode analysis of trace H2O2 based on Fe-doped carbon dot catalytic oxidation of TMB

A stable Fe-doped carbon dot (CDFe) nanosol with high catalytic activity was prepared by water hydrothermal procedure using ferrocene as precursor. In Tris-HCl buffer solution, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized slowly by H2O2 that catalyzed quickly by CDFe. The oxidation product (TMBox) molecular probes exhibit surface-enhanced Raman scattering (SERS) peak at 1606 cm−1 in the silver nanosol substrate, fluorescence (Flu) peak at 400 nm and absorption (Abs) peak at 560 nm. With the increase of H2O2 concentration, the produced TMBox increased, and the SERS/Flu/Abs peaks were enhanced linearly. Based on this, a new SERS/Flu/Abs trimode molecular spectral method was established for the determination of trace H2O2 based on CDFe catalytic amplification. The results show that the SERS linear range for H2O2 concentration is 5.0 × 10−10–2.5 × 10−8 mol/L, and the detection limit is 2.52 × 10−10 mol/L. The H2O2 contents in food samples were analyzed by this SERS quantitative method, with relative standard deviations of 2.1–4.3 % and recovery of 94.5−103.8 %.

Investigation of Genotoxic and Cytotoxic Effects of Hydrogen Peroxide(The Importance of DNA Repair in Oxidative Stress)

Oxidative stress-induced reactive oxygen species induce DNA damages that may result in cell death and DNA mutations. In this study, a genotoxic and cytotoxic potential of hydrogen peroxide as a ROS generator, and the effect of cell repair of oxidative stress in TK6 cells were investigated by in vitro micronucleus assay. Cell repair was inhibited by using cytosine earabinoside. Cellular responses to different concentrations of hydrogen peroxide were evaluated by generating dose-response curves. The incidence of increased MN concentrations due to increased H2O2concentrations did not allow the identification of a plateau region. A similar curve pattern was also observed with the repair inhibited group. However, damage caused by H2O2was significantly higher (p<0.001) in the cells with repair inhibition. This demonstrates the importance of DNA repair in the observation of oxidative stress. Proliferative indexes did not change due to increasing H2O2 concentrations in both groups. But the curve of repair inhibited cells was significantly higher (p<0.001) than the curve of repair efficient cells. BN and multinucleate cell counts showed decreases with increasing ROS levels generated by H2O2. But these decreases were not reflected in proliferative index scores. This may be due to H2O2-induced apoptosis, which results in the overestimation of PI values in increasing H2O2concentrations.

The role of reactive oxygen species and nitric oxide in the formation of root cortical aerenchyma under cadmium contamination.

The present study aimed to evaluate root cortical aerenchyma formation in response to Cd-driven hydrogen peroxide (H2 O2 ) production and the role of nitric oxide (NO) in the alleviation of Cd oxidative stress in maize roots and its effects on aerenchyma development. Maize plants were subjected to continuous flooding for 30 days, and the following treatments were applied weekly: Cd(NO3 )2 at 0, 10, and 50 μM and Na2 [Fe(CN)5 NO]·2H2 O (an NO donor) at 0.5, 0.1, and 0.2μM. The root biometrics; oxidative stress indicators H2 O2 and malondialdehyde (MDA); and activities of catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were analyzed. The root dry and fresh masses decreased at higher concentrations of NO and Cd. H2 O2 also decreased at higher NO concentrations; however, MDA increased only at higher Cd levels. SOD activity decreased at higher concentrations of NO, but CAT activity increased. Aerenchyma development decreased in response to NO. Consequently, NO acts as an antagonist to Cd, decreasing the concentration of H2 O2 by reducing SOD activity and increasing CAT activity. Although H2 O2 is directly linked to aerenchyma formation, increased H2 O2 concentrations are necessary for root cortical aerenchyma development.

An Electropolymerized Self Assembled Monolayer of Crystal Violet for Chemiresistive Hydrogen Peroxide Sensor

Chemiresistive sensors have been widely used for gas sensing but recently few studies have reported their use in liquids. Unlike electrochemical sensors, these sensors are simple to fabricate and operate with a single sensing film electrodes with two electrical contacts for monitoring change in current under a small potential bias, without the need of reference electrode. Hydrogen peroxide (H2O2) is an intermediate molecule generated in numerous peroxidase assays. Therefore, it is widely used for detecting multiple biomolecules like glucose, galactose etc. H2O2 detection is commonly performed using colorimetric and electrochemical sensors. However, colorimetric sensors require chemicals while electrochemical sensors need reference electrode for reliable measurements [1].Here, we demonstrated a reagent less H2O2 sensor fabricated using carbon nanotube (CNT) as the base substrate and an electropolymerized self assembled monolayer crystal violet as selective ligand. The functionalised 2D percolation network of CNT film transduces a selective response for H2O2. The chemiresistive sensor was fabricated using a low-cost xurography based fabrication process. The CNT dispersion was supplied by Nano-C, Inc. A diluted CNT dispersion (4% v/v) was prepared by sonicating the CNT ink in a mixture of methanol and water (1:1) for 15 minutes in a bath sonicator. The diluted CNT dispersion was drop casted on a frosted glass substrate and cured at 120 oC for 60 minutes. Patterned gold leaf was used as the contact electrodes and copper tape was used for the external electrode (Figure 1a). The sensor fabrication process is described in details elsewhere [2]. The electrodes were functionalized with a self assembled monolayer by immersing them in 0.6 mM crystal violet prepared in 0.1 M phosphate buffer for 90 minutes. Then, the self assembled monolayer of crystal violet was electropolymerized using cyclic voltammetry from 0 to 2V and scan rate of 0.1 V/s.The sensor response was tested in five different H2O2 concentrations (0.5 ppm, 5 ppm, 50 ppm, 500 ppm, and 1000 ppm). H2O2 solutions were prepared by diluting the stock solution in 39 mM acetate buffer similar to the buffer strength of blood. The sensor response for various H2O2 concentrations is shown in Figure 1b. The sensor response for each H2O2 solution was calculated with 39 mM acetate buffer as the baseline. Each bar graph represents the average of last-minute current measurements of a 30 minutes run. The sensor exhibited an increase in current value with increase in H2O2 concentration from 0.5 ppm to 1000 ppm. The crystal violet attached on the CNT film undergoes oxidation in presence of H2O2 concentration. The change in oxidation state of crystal violet resulted alterations in doping level of functionalized CNT network leading to a change in conductivity of the sensor. No significant interference was observed for common interferents like as glucose, galactose, urea, uric acid and gluconic acid. The sensor was also chemically reset using 0.1 M ascorbic acid by reducing the oxidized crystal violet.We demonstrated that an electropolymerized self assembled monolayer of crystal violet attached to CNT can measure H2O2 concentration within a range of 0.5 ppm to 1000 ppm. In addition, the low-cost fabrication process and the peroxide sensor enables this technology to a wide range of peroxidase based enzymatic assays that are biological relevant both in medical diagnostics biological research.

Modification of gingival proteoglycans by reactive oxygen species: potential mechanism of proteoglycan degradation during periodontal diseases

Reactive oxygen species (ROS) overproduction and oxidative stress are increasingly being implicated in the extracellular matrix (ECM) degradation associated with chronic inflammatory conditions, such as periodontal diseases. The present study investigated the effects of ROS exposure on the proteoglycans of gingival tissues, utilizing an in vitro model system comprised of supra-physiological oxidant concentrations, to ascertain whether gingival proteoglycan modification and degradation by ROS contributed to the underlying mechanisms of ECM destruction during active gingivitis. Proteoglycans were purified from ovine gingival tissues and exposed to increasing H2O2 concentrations or a hydroxyl radical (·OH) flux for 1 h or 24 h, and ROS effects on proteoglycan core proteins and sulfated glycosaminoglycan (GAG) chains were assessed. ROS were capable of degrading gingival proteoglycans, with ·OH species inducing greater degradative effects than H2O2 alone. Degradative effects were particularly manifested as amino acid modification, core protein cleavage, and GAG chain depolymerization. Proteoglycan core proteins were more susceptible to degradation than GAG chains with H2O2 alone, although core proteins and GAG chains were both extensively degraded by ·OH species. Proteoglycan exposure to ·OH species for 24 h induced significant core protein amino acid modification, with decreases in glutamate, proline, isoleucine, and leucine; and concomitant increases in serine, glycine, and alanine residues. As clinical reports have previously highlighted proteoglycan core protein degradation during chronic gingivitis, whereas their sulfated GAG chains remain relatively intact, these findings potentially provide further evidence to implicate ROS in the pathogenesis of active gingivitis, complementing the enzymic mechanisms of periodontal tissue destruction already established.