High Concentrations Of Hydrogen Peroxide Research Articles

Influence of smoking on oral cells genotoxicity after at-home bleaching using 22% carbamide peroxide: a cohort study.

ObjectiveThis study evaluated the influence of smoking on the oral cells genotoxicity before and after at-home bleaching using 22% carbamide peroxide (CP).Materials and methodsThis is a prospective observational analytics cohort study which evaluated nonsmokers (NS; n = 24) and smokers (S; n = 16) patients. At-home bleaching was performed using 22% CP gel in individual trays for 1 h per day for 14 days in both groups. Scrapped cells from marginal gums were collected before the bleaching treatment (D0-baseline) and 1 day (D1), 15 days (D15), and 1 month (D30) after its finishing. Cells were stained with Giemsa 10%, and the micronucleus (MN) and metanuclear alterations (MA) were counted by a trained operator in 1000 cells per patient. The collections and data analysis occurred blindly. Data was analyzed by Kruskal–Wallis, Dunn, and Mann–Whitney test (α = 0.05).ResultsMN frequency was not influenced by smoking or bleaching. An increase of MA was observed between D0 and D30 for both groups (p < 0.001); however, no statistical difference was found between NS and S (p > 0.05) in the evaluation times.ConclusionSmoking associated with 22% carbamide peroxide gel for at-home bleaching does not show genotoxic potential analyzed by the MN counts. However, a significant increase of MA was found for smokers and nonsmokers.Clinical relevanceDespite of the increase in MA, smoking associated with 22% CP peroxide at-home bleaching showed no important genotoxic potential (MN) for oral cells. Therefore, at-home bleaching treatment is safe for nonsmokers and smokers even with a high carbamide peroxide concentration of 22%.

Photothermal-Enhanced Fenton-like Catalytic Activity of Oxygen-Deficient Nanotitania for Efficient and Safe Tooth Whitening.

The growing demand for charming smiles has led to the popularization of tooth bleaching procedures. Current tooth bleaching products with high-concentration hydrogen peroxide (HP, 30-40%) are effective but detrimental due to the increased risk of enamel destruction, tooth sensitivity, and gingival irritation. Herein, we reported a less-destructive and efficient tooth whitening strategy with a low-concentration HP, which was realized by the remarkably enhanced Fenton-like catalytic activity of oxygen-deficient TiO2 (TiO2-x). TiO2-x nanoparticles were synthesized with a modified solid-state chemical reduction approach with NaBH4. The Fenton-like activity of TiO2-x was optimized by manipulating oxygen vacancy (OV) concentration and further promoted by the near-infrared (NIR)-induced photothermal effect of TiO2-x. The TiO2-x sample named BT45 was chosen due to the highest methylene blue (MB) adsorption ability and Fenton-like activity among acquired samples. The photothermal property of BT45 under 808 nm NIR irradiation was verified and its enhancement on Fenton-like activity was also studied. The BT45/HP + NIR group performed significantly better in tooth whitening than the HP + NIR group on various discolored teeth (stained by Orange II, tea, or rhodamine B). Excitingly, the same tooth whitening performance as the Opalescence Boost, a tooth bleaching product containing 40% HP, was obtained by a self-produced bleaching gel based on this novel system containing 12% HP. Besides, negligible enamel destruction, safe temperature range, and good cytocompatibility of TiO2-x nanoparticles also demonstrated the safety of this tooth bleaching strategy. This work indicated that the photothermal-enhanced Fenton-like performance of the TiO2-x-based system is highly promising in tooth bleaching application and can also be extended to other biomedical applications.

Influence of Bleaching Gel Peroxide Concentration on Color and Penetration through the Tooth Structure

The purpose of this study was to assess the effect of hydrogen peroxide concentration on the bleaching efficacy and penetration through the tooth structure. One hundred enamel/dentin specimens with cylindrical shape were obtained from bovine incisors. The surfaces were polished and the size standardized. They were divided into five groups (n = 20), following the concentration of hydrogen peroxide in the bleaching gels: 20, 25, 30, 35, and 40% (w/w). The specimens were placed over artificial pulpal chambers containing acetate buffer solution and bleached for 30 minutes (three applications of 10 minutes each). Aliquots of the acetate solution were collected, and the peroxide concentration was measured by an analytic spectrophotometer. The color of the samples was analyzed using a colorimetric spectrophotometer at the baseline and 7 days after the bleaching procedure. The color difference was calculated using the ∆Eab formula. The data were analyzed by one-way ANOVA and Tukey's test (p <0.05). The peroxide concentrations of 20-30% showed smaller bleaching effect than the higher concentrations (p = 0.001). The peroxide penetration was significantly higher (p = 0.001) for the more concentrated gels (35 and 40%). The higher peroxide concentrations enhance the bleaching efficacy, but also increased the peroxide penetration through the tooth structure. In-office bleaching gels with higher concentrations of hydrogen peroxide (35 and 40%) present superior whitening efficacy. Nevertheless, they might also intensify the negative biological effects on the pulpal tissue, since they exhibit increased penetration potential. How to cite this article: Torres CRG, Zanatta RF, Godoy MMM, et al. Influence of Bleaching Gel Peroxide Concentration on Color and Penetration through the Tooth Structure. J Contemp Dent Pract 2021;22(5):479-483.

Treatment of Azole-Containing Industrial Wastewater by the Fenton Process

Some semiconductor fabrication processes generate high-strength wastewater that may contain high concentrations of azoles, amines, hydrogen peroxide, organic, and inorganic co-contaminants, making the treatment of this wastewater challenging. In this study, the Fenton process was utilized for the treatment of 53 mM pyrazole and 34 mM 2-(2-aminoethoxy) ethanol (known as diglycolamine, DGA) in a lab-prepared aqueous mixture containing 3.5 M hydrogen peroxide and 16 mM inorganic fluoride. The effects of operational variables for the Fenton process, such as temperature (10, 18, or 25 °C), iron dosing (32.3, 37.3, or 74.5 mM), and pH (2.5, 3.0, or 3.5), on the degradation rates were investigated. The chosen variables were then used to treat wastewater from a semiconductor fabrication facility. The Fenton process was effective in treating both the lab-prepared mixture and semiconductor industrial wastewater. The degradation of pyrazole and DGA yielded a range of byproducts including inorganic ions and organic acids.

Upconverted Metal-Organic Framework Janus Architecture for Near-Infrared and Ultrasound Co-Enhanced High Performance Tumor Therapy.

Strict conditions such as hypoxia, overexpression of glutathione (GSH), and high concentration of hydrogen peroxide (H2O2) in the tumor microenvironment (TME) limit the therapeutic effects of reactive oxygen species (ROS) for photodynamic therapy (PDT), chemodynamic therapy (CDT), and sonodynamic therapy (SDT). Here we fabricated a biocatalytic Janus nanocomposite (denoted as UPFB) for ultrasound (US) driven SDT and 808 nm near-infrared (NIR) light mediated PDT by combining core-shell-shell upconversion nanoparticles (UCNPs, NaYF4:20%Yb,1%Tm@NaYF4:10%Yb@NaNdF4) and a ferric zirconium porphyrin metal organic framework [PCN-224(Fe)]. Our design not only substantially overcomes the inefficient PDT effect arising from the inadequate Förster resonance energy transfer (FRET) process from UCNPs (donor) to MOFs (acceptor) with only NIR laser irradiation, but also promotes the ROS generation via GSH depletion and oxygen supply contributed by Fe3+ ions coordinated in UPFB as a catalase-like nanozyme. Additionally, the converted Fe2+ from the foregoing process can achieve CDT performance under acidic conditions, such as lysosomes. Meanwhile, UPFB linked with biotin exhibits a good targeting ability to rapidly accumulate in the tumor region, verified by fluorescence imaging and T2-weighted magnetic resonance imaging (MRI). In a word, it is believed that the synthesis and antitumor detection of UPFB heterostructures render them suitable for application in cancer therapeutics.

Ph stability of four hydrogen peroxide bleaching gels at different time intervals

The aim of this in vitro study was to evaluate the pH of four bleaching agents based on high concentration hydrogen peroxide (30-35%) Whiteness HP Maxx (HPM), Lase Peroxide (LP), Whiteness HP Automixx (HPA) and Dash (DA) in different clinical periods (baseline, 15', 30' and 45'). 40 specimens (bovine teeth) were divided into 4 groups; one group for each bleaching agent. Each bleaching agent was prepared according to the manufacturer's instructions and was applied on the vestibular surface. The pH of the bleaching agent was measured with a digital pH meter at baseline, 15, 30 and 45 minutes. ANOVA, Friedman and Wilcoxon tests were applied. The pH values showed a trend to decreasing from the initial time of application to the final time, except for the DA group, which showed increasing pH values over time. The HPM group showed significant differences between baseline and the remaining periods. The LP group LP showed significant difference between 15' and the other periods. The HPA group showed significant differences between baseline and the remaining periods. Finally, the DA group, showed a significant difference between baseline and 45'. The pH values of 3 of the bleaching agents decreased over time, with the exception of Dash which increased in the different time periods.

Application of solar-based oxidation to the management of empty pesticide container rinse water in Bolivia.

Background: The management of empty pesticide containers (EPC) in Bolivia has been recently promoted as a control strategy for dispersed pollution in surface and underground water bodies, as well as in soil. It comprises the rinsing and proper disposal or reuse of clean EPC. However, the rinsing transfers the hazard to water, which must be properly treated before being discharged. Methods: In this study, solar photo-Fenton at low Fe 2+ doses were tested at pilot plant scale in Cochabamba (Bolivia) for the removal of pesticides dimethoate and atrazine in their commercial form, spiked in river water. Results: The results demonstrated that solar photo-Fenton ([H 2O 2] 0 = 200 mg L -1) with Fe 2+ concentrations between 0.5 and 1.5 mg L -1 is an effective method to remove dimethoate and atrazine, at an initial concentration of 10 mg L -1 each. Efficiency increased when increasing Fe 2+ doses, achieving a removal over 99% of both pesticides after a solar irradiation period of 60 minutes (corresponding to an accumulated energy of 4.96 kJ L -1). Conclusions: The presence of high concentrations of natural components of river water, mainly organic and inorganic carbon species, would have contributed to hydroxyl radical scavenging, explaining, together with the low iron dose applied, the high energy (irradiation time) and high hydrogen peroxide concentration required to produce pesticide depletion. Additionally, the relatively low oxidant consumption and mineralization observed leave room for process optimization regarding oxidant and catalyst doses and warrant further studies on its coupling with biological or other post-treatments for the removal of transformation products.

Electrochemical mineralization of iron-tannate stain on HAp and bovine enamel-A non-peroxide approach

Prolonged treatments for the destaining of teeth using high concentrations of hydrogen peroxide may cause secondary unwanted effects such as tooth hypersensitivity and gingival irritation. Hence, it is aimed to develop a non-peroxide-based method to oxidize iron-tannate (Fe-TA) stained hydroxyapatite (HAp) and bovine enamel (BE) samples. Constant current electrolysis (CCE) experiments were carried out on Pt working electrode in aqueous NaCl, KCl and KI solutions at discrete concentrations under continuous experiment and a non-continuous experiment. CCE shows that in the presence of iron tannate (Fe-TA) stained HAP, approximately 30 ppm of iodine was generated using 0.1M KI and nearly 40 ppm was produced with 0.2 M KI. By using a non-continuous CCE process, the lowest amount of chlorine was generated from NaCl solution, which was well within the safety limits for oral applications. Depending on the experimental conditions used, between 13 ppm and 124 ppm of chlorine was generated. CCE of Fe-TA stained on HAp using KCl reveals that at the lowest current density of 10 mA/cm2, the amount of hypochlorite generated was 20 ppm on Pt electrode having a surface area of 6 cm2. Ion chromatographic (IC) analysis revealed that non-continuous CCE of Fe-TA-BE in NaCl generated a low concentration of sodium perchlorate (0.8 ppm), whereas the continuous process generated no perchlorate, but a considerable higher quantity of chlorate for Fe-TA-BE (37 ppm) and Fe-TA-HAp (140 ppm) samples.

Iron oxide-based enzyme mimic nanocomposite for dual-modality imaging guided chemical phototherapy and anti-tumor immunity against immune cold triple-negative breast cancer

Triple-negative breast cancer has few biomarkers to guide benefit from immunotherapy; furthermore, the biochemical features of the tumor microenvironment including acidosis, hypoxia, and high hydrogen peroxide concentrations, significantly modulate cancer cell metabolism and metastatic potential, and associate with bad outcomes from chemo-radiotherapy and surgery. Herein, a theranostic nanocomposite with a dual imaging modality and chemical phototherapeutic capacity has been used for breast cancer cell inhibition, which is developed to self-assemble superparamagnetic iron oxide nanocrystals and IR-780 iodides in one system. Due to the magnetic resonance and near-infrared Ⅱ fluorescence capacity, this nanocomposite serves as a contrast agent for the high-sensitivity, accurate cancer diagnosis and facilitates imaging-guided phototherapy. Furthermore, this nanocomposite not only performs dual enzyme-like activities in the tumor microenvironment, but also carries out the bioeffect of hyperthermia and oxidative stress, which could repolarize tumor-associated macrophages from the tumor-promoting M2 phenotype into the tumoricidal M1 phenotype, reduce the number of immunosuppressive cells, and execute immune activation. Through simultaneous chemical phototherapy and anti-tumor immunity, this iron oxide-based nanocomposite successfully suppresses tumor growth and metastasis, and has good biocompatibility in normal tissues and organs; thus, it might provide new insights into the development of a novel cancer therapy strategy.

Physiological and biochemical changes in wheat plants infected by Pyricularia oryzae caused by thermal oscillations

Physiological and biochemical changes in plants exposed to high temperatures may lower their resistance to diseases. In this regard, this study investigated whether thermal oscillations could change wheat resistance to blast, caused by Pyricularia oryzae, considered one of the most important diseases affecting wheat production. Plants were kept in two growth chambers with temperatures of 19 and 28 °C each for five days for thermal acclimatization and inoculated with P. oryzae after that. After inoculation, groups of plants were transferred to their original growth chambers (19 and 28 °C) and switched to growth chambers with temperatures different from those used for acclimatization (from 19 °C to 28 °C and from 28 °C to 19 °C) during three days. Plants subjected to thermal condition (TC) of 19 °C→19 °C compared to TC of 28 °C→28 °C showed lower blast symptoms. Photosynthetic impairment (lower maximum photosystem PSII photochemical efficiency, effective PSII quantum yield, quantum yield of non-regulated energy dissipation and stomatal conductance values and high internal CO2 concentration) and lower concentrations of total chlorophyll a+b and carotenoids were noticed for plants subjected to 28 °C before or after inoculation. Inoculated plants subjected to TC of 28 °C→28 °C showed higher superoxide dismutase and lower ascorbate peroxidase activities. Lower superoxide anion and high hydrogen peroxide concentrations occurred for inoculated plants subjected to TC of 28 °C→28 °C. Higher chitinase, phenylalanine ammonia-lyase, and peroxidase activities occurred for inoculated plants subjected to TC of 28 °C→28 °C and 19 °C→28 °C and lower polyphenoloxidase activity for inoculated plants subjected to 28 °C after or before inoculation. Plants continuously subjected to 28 °C, before or after inoculation, displayed remarkable damage to their photosynthetic apparatus, a less robust antioxidative system, and a minor contribution of defense-related enzymes to counteract the deleterious effect of P. oryzae infection.

Nitrogen-Doped Titanium Dioxide Mixed with Calcium Peroxide and Methylcellulose for Dental Bleaching under Visible Light Activation

The available tooth whitening products in the market contain high concentrations of hydrogen peroxide (H2O2) as an active ingredient. Therefore, in order to curb the high H2O2 concentration and instability of liquid H2O2, this study evaluated the efficacy and cytotoxicity of the bleaching gel composed of 10% calcium peroxide (CaO2) and visible-light-activating nitrogen-doped titanium dioxide (N-TiO2) with methyl cellulose as a thickener. Extracted bovine teeth were discolored using coffee and black tea stain solution and were divided into two groups (n = 6). Bleaching was performed thrice on each tooth specimen in both the groups, with one minute of visible light irradiation during each bleaching time. The CIELAB L*a*b* values were measured pre- and post-bleaching. The N-TiO2 calcinated at 350 °C demonstrated a shift towards the visible light region by narrowing the band gap energy from 3.23 eV to 2.85 eV. The brightness (ΔL) and color difference (ΔE) increased as bleaching progressed each time in both the groups. ANOVA results showed that the number of bleaching significantly affected ΔE (p < 0.05). The formulated bleaching gel exhibits good biocompatibility and non-toxicity upon exposure to 3T3 cells. Our findings showed that CaO2-based bleaching gel at neutral pH could be a stable, safe, and effective substitute for tooth whitening products currently available in the market.

REMINERALIZING THERAPY IN THE PROCESS OF TEETH WHITENING

Resume. Nowadays, aesthetics plays an important role in dentistry due to the increased attention of people to the beauty and attractiveness of the smile, which is known as an effective tool in achieving both personal and professional purposes. Therefore, the whitening of discolored teeth is one of the promising directions in aesthetic dentistry. To date, there is much controversy among dentists about the effectiveness and, the most importantly, the safety of teeth whitening. The prevention of dentin hypersensitivity is among the main tasks associated with the safe and comfortable treatment and follow-up period for patients. In order to avoid the negative consequences of hyperesthesia, the teeth whitening procedure should be finished with remineralizing therapy. Thought there are a large number of techniques and products for the treatment of hyperesthesia, the question of their most appropriate selection and combination is remaining unresolved and is relevant to meet the steadily growing population demands.&#x0D; Purpose: to highlight the latest views on techniques and products for remineralizing therapy in the process of teeth whitening based on the analysis of relevant literature.&#x0D; Results. Numerous bleaching methods are mainly based on applying high concentrations of hydrogen peroxide. At present, the safety of whitening methods remains controversial and thus requiring further research. The problem of improving techniques aimed at preventing the side effects of professional whitening on the oral tissues and organs are remaining relevant. The problems associated with professional whitening include the decreased resistance of hard dental tissues, the appearance of areas of demineralization and hyperesthesia in the hard dental tissues. At present, a wide range of products has been proposed to treat and prevent the development of teeth hypersensitivity. However, the most effective of them, which could be offered to patients after professional whitening have not been identified yet. To prevent and treat dental hyperesthesia effectively, fluoride-containing remineralizing remedies are widely used to diminish dentin sensitivity. There are studies demonstrating the highest incidence of teeth hyperesthesia during light catalytic and chemical bleaching Therapeutic and prophylactic agents, which contain calcium, phosphorus and fluoride ions, which promote dental enamel remineralization, have been proposed. The use of remineralizing gels before the procedure of medical teeth whitening reduces the occurrence of dental hyperesthesia. That is why many manufacturers of bleaching systems have begun to add desensitizing components to their composition. Thus, Opalescence Boost PF gel contains potassium nitrate and fluorine, Philips Zoom whitening gel contains amorphous calcium phosphate, in addition; remineralizing gel Relief ACP with amorphous calcium phosphate is offered to reduce the occurrence of teeth hypersensitivity during whitening procedure. The results of our research have shown the most significant changes expressed by a decrease in organic acids, maximum increase in concentrations of calcium ions in oral fluid, occur when using photo-bleaching system Beyond Polus, while minimal changes are observed when using chemical activation system Opalescence Xtra Boost. The combination of a reminalizign remedies based on zinc-substituted hydroxyapatite carbonate with laser phonophoresis can be recommended be apply after any bleaching techniques and they have been proved to be the most effective.&#x0D; Conclusion. There is a wide range of techniques and products of remineralizing therapy applied in the process of teeth whitening. Various options of remineralizing therapy and applying different compounds reducing teeth sensitivity after teeth whitening procedure are described in the article. Many formulas have been already developed to ensure patient comfort after a whitening procedure, and in particular to prevent the development of hyperesthesia. Some manufacturers incorporate remineralizing remedies in the whitening system that allows dentists to solve the problem of teeth hypersensitivity effectively.

Effect of diode laser-assisted bleaching on the bond strength of different adhesive systems to enamel: Interfacial SEM analysis.

The aim of this study was to investigate the effectiveness of diode laser-assisted bleaching on the shear bond strength (SBS) of different adhesive systems to enamel and examine the adhesive enamel interface under scanning electron microscope (SEM). 180 incisor teeth were randomly divided into three bleaching groups: (1) Unbleached control group, (2) Opalescence Boost (OB) 40%, and (3) Diode laser-assisted LaserWhite20 (LW20) 45%. After bleaching, each group was divided into two subgroups according to waiting time: immediately or 7 days' delay. The six groups were then divided into three subgroups based on the adhesive procedure: Single Bond 2 (SB2), Clearfil SE Bond (CSB), and Clearfil Universal Bond (CUB). After adhesive procedures, composite resin cylinders were bonded to the enamel surfaces. All specimens were subjected to a SBS test after 24 hr of storage in water. Data were analysed using three-way variance analysis (p < .05). Specimens were examined under a stereomicroscope and SEM. There was a significant difference between the groups bonded immediately and 7 days after bleaching (p < .05). SB2 after 7 days showed the highest SBS values (19.24 ± 2.18), whereas CUB showed the lowest values in both bleaching treatments and control groups (10.84 ± 1.66). SEM analysis of the unbleached specimens revealed long tags and uniform hybrid layer compared OB and LW20 bleaching groups. LW20 and OB bleaching adversely affected SBS to enamel when bonded immediately. Diode laser-assisted bleaching might be an alternative option due to the short working time but delaying bonding for 7 days after bleaching may not be enough for ideal adhesion. RESEARCH HIGHLIGHTS: Bleaching agents containing high concentration hydrogen peroxide reduces the enamel bond strength of adhesive systems. Postponing composite restorations for 7 days after bleaching may not be sufficient to achieve ideal adhesion. Diode laser-assisted bleaching may be preferred as an alternative bleaching method today due to its ability to shorten the operation time and cause minimal morphological changes on the enamel surface.

Surface properties of resin-modified glass-ionomers subjected to in-office bleaching agents

This study examined the influence of two in-office bleaching on surface roughness, topography and microhardness of RMGIs. Disc-shape samples of RMGIs (Ketac N100, Fuji II LC-Capsule, and Photac Fil Quick Aplicap) were prepared and polymerized by a LED light curing unit. Polished samples, were subjected to in-office bleaching agents, Opalescence Xtra Boost (OXB) and Pola Office (PO), for 3 consecutive applications of 15 min each. The surface roughness parameters (R a and R max, μm) and Knoop hardness number (KHN, kg/mm2) were measured using contact profilometer and microhardness tester, respectively. The surface topography of the bleached surfaces was evaluated by SEM. Two-way ANOVA demonstrated high significant differences between the KHN, R a and R max values among the RMGIs and the bleaching agents evaluated as well as their interactions (p < 0.05). Pearson’s correlation indicated mainly no significant correlation between KHN and R a surface finish at each in-office agent for each RMGI (p > 0.05). Low R a (0.193 µm) and high KHN (49.34) values were presented in N100, whereas high R a (0.916 µm) and low KHN (31.54) were found in PFQ and FII, respectively, after bleaching with OXB. Surface properties are affected by the differences in material’s composition, mainly fillers, and type of bleaching agent. High concentration of hydrogen peroxide from bleaching agent and type of RMGIs can influence the chemical softening of these restorations and their clinical durability.

Synthesis and characterization of enzymatically active micrometer protein-capsules

This work describes a general method for the encapsulation of enzymes with albumin as wall material and the enzyme catalase as prime example. Care was taken for the preparation of biochemically active sub-micrometer particles in order to prevent oxygen toxicity induced by artificial oxygen carriers of any type. In cell culture experiments, capsules containing catalase did not exhibit any harmful activities in the absence of peroxides. In the presence of hydrogen peroxide application of low and medium dosed capsules below 0.05 vol% (final concentration 0.001 vol%) even increased the cell damaging process. However, a higher dosage of capsules (>0.05 vol%) prevented completely cellular disruption induced by 5 mM hydrogen peroxide and decreased up to 90% of cellular damage at higher peroxide concentrations. These results demonstrated that encapsulated catalase was enzymatically active and the over-all activity of prepared catalase capsules was determined to be >1900 U mL−1 vol%−1.

Peroxidase activity of hemoglobin and heme destruction in the presence of hydrogen peroxide and CT-DNA

The aim of this study was to investigate the peroxidase activity of Hb with different concentrations of hydrogen peroxide and compare it with hypochlorous acid effect on Hb. Hypochlorous acid at higher concentrations decomposed Hb and heme, releasing fee iron ion from the metal center. High concentrations of hydrogen peroxide switched the peroxidase activity of Hb towards the partial Hb and heme destruction. Heme alone was degraded showing that the Hb conformation and protein environment protects Hb from the distraction in the presence of highly increased hydrogen peroxide concentration that occurs as a result of oxidative stress. In the presence of CT-DNA acted inhibition of the peroxidase activity of Hb was observed signaling inhibited hydrogen peroxide consumption.

Reactive wetting of polyethylene on ethylene-propylene-diene terpolymer

If wetting is ubiquitous in nature, reactive wetting is up to now mostly described for metallic and ceramic systems. Characterizing wetting between two reactive organic polymers is more challenging due to their similar molecular structure and yet it is crucial to unravel adhesion mechanisms. This is for example the case when combining ethylene-propylene-diene terpolymer (EPDM) with polyolefins like polyethylene (PE). Therefore, in this study, a high temperature contact angle measurement methodology is presented to evidence the occurrence of chemical bonds at the interface. Spreading of PE was found to be restricted on vulcanizing peroxide-based EPDM, while on an already completely vulcanized EPDM, low static advancing contact angles were obtained. This restriction in wetting is ascribed to a co-vulcanization reaction between EPDM and PE. Furthermore, the chemical bonding mechanism is even more pronounced with higher peroxide concentrations in EPDM which also leads to a higher adhesion strength at the interface.

Ionizing-radiation-resistant Kocuria rhizophila PT10 isolated from the Tunisian Sahara xerophyte Panicum turgidum: Polyphasic characterization and proteogenomic arsenal

A new strain belonging to the genus Kocuria, designed PT10, was isolated from irradiated roots of the xerophyte Panicum turgidum. Isolate PT10 is a Gram-positive, coccoid, aerobic and ionizing-radiation (IR)-resistant actinobacterium. PT10 has shown an ability to survive under extreme conditions, such as gamma irradiation, desiccation and high concentration of hydrogen peroxide. Phenotypic, chemotaxonomic and comparative genome analyses support the assignment of strain PT10 (LMG 31102 = DSM 108617) as Kocuria rhizophila. The complete genome sequence of PT10 consists of one chromosome (2,656,287 bps), with a 70.7% G + C content and comprises 2481 protein-coding sequences. A total of 1487 proteins were identified by LC-MS/MS profiling. In silico analyses revealed that the proteome of the oxidation-tolerant PT10 possesses several features explaining its IR-resistant phenotype and many adaptive pathways implicated in response to environmental pressures — desiccation, cold, reactive oxygen species and other stressors.

Improvement of endothelial function by Gunnera tinctoria extract with antioxidant properties

BackgroundGunnera tinctoria has been collected by Mapuche-Pewenche people for food and medicinal purposes. The high polyphenol content of methanolic extract from G. tinctoria leaves with chemical constituents such as ellagic acid and quercetin derivatives suggests its application to prevent endothelial dysfunction and oxidative stress. The aim of this study was to provide evidence of the protective effect of this extract on endothelial function by reducing oxidative stress induced by high d-glucose and H2O2, as well as by stimulating nitric oxide (NO) levels in human umbilical vein endothelial cells (HUVECs).ResultsA methanolic extract with a high content of polyphenols (520 ± 30 mg gallic acid equivalents/g dry extract) was obtained from G. tinctoria leaves. Its main constituent was ellagic acid. The results of Ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays of the extract confirmed its antioxidant activity by inhibition pathway of radical species. The incubation of HUVECs with the extract decreased the apoptosis and reactive oxygen species (ROS) synthesis induced by high extracellular concentration of d-glucose or hydrogen peroxide. The extract increased endothelial NO levels and reduced vasoconstriction in human placental vessels.ConclusionsThis study provides evidence about the antioxidant and endothelial protective properties of methanolic G. tinctoria leaf extract. The extract improves the availability of NO in HUVECs, inhibiting the production of ROS and vasoconstriction.

Potassium and calcium improve salt tolerance of Thymus vulgaris by activating the antioxidant systems

Thyme (Thymus vulgaris L.) is an important wild aromatic plant of the Mediterranean region which also has wide-ranging therapeutic properties. Its growth and chemical properties can be modified by agricultural practices especially mineral nutrition and irrigation. An experiment was undertaken to determine the effectiveness of exogenous foliar application of potassium and calcium against the adverse effects of NaCl-induced stress on Thyme. Salt stress decreased growth and photosynthetic assimilation rate. Leaf spray with K+ or Ca2+ reduced salt-induced damage by maintaining K+/Na+ and Ca2+/Na+ ratios, resulting in photosynthesis improvement under salt conditions. Salt-affected plants had higher concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in their shoot tissues indicating oxidative damage to their cell membranes; Increased K+ and Ca2+ supply reduced the accumulation of both. Salinity appears to have upregulated the activity of antioxidant defense enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase, glutathione reductase, peroxide guaiacol, Monodehydroascorbate reductase, as well as Dehydroascorbate reductase. The application of K+ and Ca2+ solutions onto the foliage of NaCl-affected plants further enhanced the activity of the antioxidant enzymes of the ascorbate glutathione cycle potentially allowing a better protection of the cell membranes from reactive oxygen species.