Low Concentrations Of Hydrogen Peroxide Research Articles

Oxidative power of aqueous non-irradiated TiO2-H2O2 suspensions: Methylene blue degradation and the role of reactive oxygen species

In the present study, the degradation of methylene blue in non-irradiated TiO2-H2O2 suspensions was investigated. Five commercially available catalysts were characterized (BET surface area, zeta potential, hydrodynamic diameter) and their oxidative power was assessed by means of the degradation of methylene blue. A subsequent EPR study was made to verify and identify potential oxidative radicals. The results showed that all suspensions could degrade methylene blue significantly stronger compared to hydrogen peroxide alone. A broad variation between the different catalysts in their capability to adsorb dye molecules was found which was essential for decomposition of methylene blue in darkness. The highest degradation rate of all samples was found for Degussa P25 at neutral pH. EPR studies of this sample verified the presence of oxygen centred radicals namely hydroxyl (OH) and superoxide radicals (O2−/OOH). Non-irradiated TiO2-H2O2 systems show great potential not only in dye removal applications but also in the field of disinfection where low concentrations of hydrogen peroxide are required and irradiation may not be feasible.

Electrochemical Assessment of Sequence Selective DNA Damage from Myoglogin and Cytochrome P450 Bioactivated Benzo[a]pyrene at TP53 Oligomers

AbstractEnzymatic bioactivation of an otherwise non‐reactive species into a reactive one can lead to significant health problems in vivo. Bioactivation of benzo[a]pyrene (BP) produces known cancer causing agents, most notably anti‐benzo[a]pyrene‐r‐7,t‐8‐dihydrodiol‐t‐9,10‐epoxide (anti‐BPDE) that has been shown to attack DNA at specific genomic sites termed hotspots. Bioactivation of BP resulting in DNA damage at a specific hotspot codon was determined electrochemically. Gold electrodes were modified with DNA 21‐mer oligomers spanning codons 270–276 of the TP53 gene as well as myoglobin (Mb) that acted as an in vivo bioactivation enzyme mimic. The electrodes were exposed to BP and low concentrations of hydrogen peroxide to activate the enzymes to produce reactive metabolites that could in turn damage the DNA. DNA damage was assayed electrochemically using square wave voltammetry (SWV) to probe a diviologen compound of the form C12H25V2+C6H12V2+C12H25 (V2+=4,4′‐bipyridyl or viologen, C12‐Viologen) that has previously been employed to study DNA damage. DNA damage was dependent on both BP concentration and on the presence of the hotspot 273‐codon guanine. Additionally, cytochrome P450 1A1 and 1A2 isoforms in bicistronic membrane fractions were utilized, and DNA damage from BP exposure followed predicted patterns based on the isoform employed.

Different effects of sonication pretreatment on carbon nanomaterials under low hydrogen peroxide concentrations

Dispersing carbon nanomaterials with the aid of sonication has become a widely used procedure for generating homogenous solutions. A systematic study was performed to evaluate the effects of a practical sample preparation procedure that involves mild sonication with/without low concentrations of hydrogen peroxide. Hydrogen peroxide is ubiquitously present in surface water and involved in advanced oxidation processes. Significant oxidation was observed for fullerene in the liquid phase, whereas an appreciable amount of hydrogen was covalently attached to the carbon cage of solid fullerene. Under the same conditions, only the removal of oxidized amorphous carbon was detected for carbon nanotubes. The presence of a low concentration of hydrogen peroxide during sonication exacerbated the effects. The changes in physicochemical properties were characterized quantitatively using X-ray photoelectron spectroscopy and elemental chemical analysis and qualitatively using matrix-assisted laser desorption ionization mass spectroscopy, 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Our results highlight the effects that can occur during sample preparation step and the potential for misinterpreting the toxicity, reactivity and environmental fate of carbon nanomaterials.

Role of peroxiredoxin2 in H2O2‑induced oxidative stress of primary Leydig cells.

Late‑onset hypogonadism is defined as a condition caused by a decline in the levels of testosterone with aging. One of the major factors contributing to the low levels of testosterone is the accumulation of reactive oxygen species (ROS) in Leydig cells during the ageing process. Peroxiredoxin2 (Prdx2), a member of the peroxiredoxin family, is an antioxidant protein, the predominant function of which is to neutralize ROS. However, its role in Leydig cells remains to be elucidated. In the present study, primary Leydig cells were exposed to low concentrations of hydrogen peroxide (H2O2) to induce oxidative stress. Cell apoptosis was measured using an AnnexinV fluorescein isothiocyanate/propidium iodide apoptosis detection kit and flow cytometry. The level of testosterone was determined by radioimmunoassay, and the mRNA and protein expression levels of Prdx2 were detected by reverse transcription‑polymerase chain reaction and western blotting, respectively. The results revealed a significant increase in cell apoptosis and decrease in testosterone production. In addition, the expression of Prdx2 was decreased by H2O2 in a dose‑ and time‑dependent manner, and this decrease may have been caused by the induction of its molecular structure transformation due to H2O2 elimination. The above findings indicated that Prdx2 may prevent H2O2 accumulation in Leydig cells, and may be important in oxidative stress‑induced apoptosis and decreased testosterone production.

Penetration Capacity, Color Alteration and Biological Response of Two In-office Bleaching Protocols.

Hydrogen peroxide (H2O2) penetrates into the dental hard tissues causing color alteration but also alterations in pulpal tissues. Hard-tissue penetration, color alteration and the pulp response alterations were evaluated for two in-office bleaching protocols with H2O2. For trans-enamel/dentin penetration and color alteration, discs of bovine teeth were attached to an artificial pulp chamber and bleached according to the groups: BLU (20% H2O2 - 1x50 min, Whiteness HP Blue); MAX (35% H2O2 - 3x15 min, Whiteness HP Maxx); Control (1x50 min, placebo). Trans-enamel/dentin penetration was quantified based on the reaction of H2O2 with leucocrystal violet and the color analyzed by CIELab System. Twenty Wistar rats were divided into two groups (BLU and MAX) and their maxillary right molars were treated according to the same protocols of the in vitro study; the maxillary left molars were used as controls. After 2 days, the animals were killed and their maxillae were examined by light microscopy. The inflammation of pulp tissue was scored according to the inflammatory infiltrate (1, absent; 2, mild; 3, moderate; 4, severe/necrosis). Data were analyzed by statistical tests (α=0.05). MAX showed higher trans-enamel/dentinal penetration of H2O2 (p<0.05). The color alteration was similar for both groups (p>0.05), and different when compared to Control group (p<0.05). MAX showed severe inflammation in the upper thirds of the coronal pulp, and BLU showed moderate inflammation (p<0.05). In-office bleaching protocols using lower concentrations of hydrogen peroxide should be preferred due to their reduced trans-enamel/dentinal penetration since they cause less pulp damage and provide same bleaching efficiency.

Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions.

Peroxidations mediated by heme-enzymes have been traditionally studied under a single-site (heme distal pocket), non-sequential (ping-pong), two-substrates binding scheme of Michaelis-Menten paradigm. We had reported unusual modulations of peroxidase and P450 reaction outcomes and explained it invoking diffusible reactive species [Manoj, 2006; Manoj etal., 2010; Andrew etal., 2011, Parashar etal., 2014 & Venkatachalam etal., 2016]. A systematic investigation of specific product formation rates was undertaken to probe the hypothesis that involvement of diffusible reactive species could explain undefined substrate specificities and maverick modulations (sponsored by additives) of heme-enzymes. When the rate of specific product formation was studied as a function of reactants' concentration or environmental conditions, we noted marked deviations from normal profiles. We report that heme-enzyme mediated peroxidations of various substrates are inhibited (or activated) by sub-equivalent concentrations of diverse redox-active additives and this is owing to multiple redox equilibriums in the milieu. At low enzyme and peroxide concentrations, the enzyme is seen to recycle via a one-electron (oxidase) cycle, which does not require the substrate to access the heme centre. Schemes are provided that explain the complex mechanistic cycle, kinetics & stoichiometry. It is not obligatory for an inhibitor or substrate to interact with the heme centre for influencing overall catalysis. Roles of diffusible reactive species explain catalytic outcomes at low enzyme and reactant concentrations. The current work highlights the scope/importance of redox enzyme reactions that could occur "out of the active site" in biological or in situ systems.

Use of a predictive protocol to measure the antimicrobial resistance risks associated with biocidal product usage

In this study we assessed the propensity of biocide exposure in the development of antimicrobial resistance in bacteria. Our protocol is based on reporting changes in established antimicrobial susceptibility profiles in biocides and antibiotics after during use exposure to a product. The during use exposure reflects worse conditions of product use during application. It differs from the term low concentration, which usually reflects a concentration below the minimal inhibitory concentration, but not necessarily a concentration that occurs in practice. Our results showed that exposure to triclosan (0.0004%) was associated with a high risk of developing resistance and cross-resistance in Staphylococcus aureus and Escherichia coli. This was not observed with exposure to chlorhexidine (0.00005%) or a hydrogen peroxide-based biocidal product (in during use conditions). Interestingly, exposure to a low concentration of hydrogen peroxide (0.001%) carried a risk of emerging resistance to antibiotics if the presence of the oxidizing agent was maintained. We observed a number of unstable clinical resistances to antibiotics after exposure to the cationic biocide and oxidizing agent, notably to tobramycin and ticarcillin-clavulanic acid. Using a decision tree based on the change in antimicrobial susceptibility test results, we were able to provide information on the effect of biocide exposure on the development of bacterial resistance to antimicrobials. Such information should address the call from the U.S. Food and Drug Administration and European Union Biocidal Products Regulation for manufacturers to provide information on antimicrobial resistance and cross-resistance in bacteria after the use of their product.

ナノ構造化バイオセンサを用いた環境汚染物質の検出

We have discussed about a novel technique of developing a nanostructured polypyrrole biosensor for measurement of very low concentrations of hydrogen peroxide in liquid media. The proposed fabrication method is very effective in growing a nanostructured conductive polymer layer on a planar conductive substrate. In addition enzyme loading was done under a high electric field of 1 kV/m. The developed sensor provides a linear range of 0-200 µmol/l of hydrogen peroxide and a measurement sensitivity of 6.5 Acm-2 (mol/l)-1.

Reactive oxygen species induce neurite degeneration before induction of cell death.

Reactive oxygen species (ROS) induce neuronal cell death in a time- and concentration-dependent manner. Treatment of cultured cells with a low concentration of hydrogen peroxide induces neurite degeneration, but not cell death. Neurites (axons and dendrites) are vulnerable to ROS. Neurite degeneration (shrinkage, accumulation, and fragmentation) has been found in neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. However, the mechanism of ROS-related neurite degeneration is not fully understood. Many studies have demonstrated the relationship between mitochondrial dysfunction and microtubule destabilization. These dysfunctions are deeply related to changes in calcium homeostasis and ROS production in neurites. Treatment with antioxidant substances, such as vitamin E, prevents neurite degeneration in cultured cells. This review describes the possibility that ROS induces neurite degeneration before the induction of cell death.

New Parameter for In-Office Dental Bleaching.

Dental bleaching is considered a conservative and biologically safe treatment for discolored teeth. Despite this, one of the major undesirable effects of bleaching is dentin sensitivity which may occur during and after treatment. To address these sensitivity issues, new dental bleaching preparations with lower concentrations of hydrogen peroxide (H2O2) have recently been introduced to the market. This paper presents a clinical case report of a 20-year-old female patient admitted to the Araraquara Dental School, UNESP, Brazil. The patient underwent dental bleaching using one of the new products with reduced hydrogen peroxide concentration, Lase Peroxide Lite 6%, a 6% H2O2 gel containing titanium oxide nanoparticles doped with nitrogen (6% H2O2/N-doped TiO2).

Association of the biochemical parameters of ejaculate with the characteristics of spermatozoa

Motility is one of the most important characteristics of spermatozoa that determine their fertilization ability. Energy for cell movement is produced through glycolysis. Oxidation of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the presence of hydrogen peroxide (10–3 mole) results in decreased sperm motility. This study investigated the impact of low hydrogen peroxide concentrations (10–4 and 10–5 mole) on GAPDH activity and sperm motility. Hydrogen peroxide in the above concentrations was shown to lead to an increase in total and active sperm motility by 11 and 19 %, respectively; and to simultaneously enhance GAPDH activity by 24 %. It may be that low hydrogen peroxidase concentrations stimulated the cellular antioxidant system. Along with altered sperm motility in another series of the investigation, the investigators determined the level of the biochemical components of ejaculate in different male genital diseases, such as varicocele and chronic prostatitis. Comparison of the sperm obtained from control donors and patients with varicocele showed a significant drop in the concentration of the enzymes aspartate aminotransferase, alanine aminotransferase, and cholinesterase. The other biochemical parameters of sperm did not substantially differ from those in the control group. The same level of biochemical parameters was also noted in the patients with chronic prostatitis. At 24 hours after incubation at room temperature, there were 24 and 33 % reductions in the concentrations of total protein and glucose, respectively. The concentration of ions in the sperm was considerably unchanged. At the same time following 24 hours, the motility of spermatozoa fell and their total and active motility was 41 and 30 % of the 100 % baseline level, respectively. The physiological role of the biochemical components of ejaculate is likely to be related to the maintained motility of spermatozoa when the latter are present in the female genital tract.

ROS-Mediated Jab1-Thioredoxin Interaction in Acute Monocytic Leukemia

SUMMARYIncreased production of reactive oxygen species (ROS) or an inefficient antioxidant system leads to oxidative stress, which influences hematopoietic cell function in acute myeloid leukemia (AML); however, the mechanisms of this stress remain poorly understood. Investigations were carried out on matched samples from the same 58 patients with AML-M5 (33 males and 25 females) who experienced a relapse after treatment. They had a median age of 43.90 ± 17.39 years (range, 14-77 years) at diagnosis and 44.86 ± 16.28 years at relapse. The mean white blood cell (WBC) counts were 16.58 x 109/L at diagnosis and 24.41 x 109/L at relapse (P < 0.05). Here, our studies showed that abnormally high ROS levels and low antioxidant enzyme capacity were characteristic of AML-M5 at both diagnosis and relapse. It is worth mentioning Jab1 and Trx protein levels were higher in all leukemia cell lines tested (THP-1, U937, and MOLM-13 cells), as well as in leukemic cells derived from AML-M5 patients, than in CD34+ cells from healthy donors (Figure 1A-D). A chi-square test revealed that patients with high Jab1 levels were less sensitive to Ara-c-based chemotherapy (Figure 1E). Consistently, high gene expression levels of thioredoxin (Trx) and Jab1 were associated with poor survival rates in AML-M5 patients(Figure 1F-H). Moreover, stimulating AML-M5 cells with a low concentration of hydrogen peroxide increased Jab1 and Trx expression. Additionally, depletion of Jab1 inhibited cellular proliferation and invasion, which was accompanied by a decrease in Trx expression.Mechanistically, we demonstrate that Jab1 controls a major antioxidative cellular molecule Trx by interacting with and enhancing its transcriptional levels through AP-1 binding sites. To assess whether Jab1 and Trx interact we performed co-immunoprecipitation assays and demonstrated that Jab1 and Trx proteins interacted specifically with each other using endogenous proteins or ectopically expressed tagged-proteins, in U937 and THP-1 cells (Figure 2A and B). Furthermore, our results demonstrate that Jab1 knockdown remarkably reduced Trx levels (Figure 2C). Inversely, Jab1 overexpression induced higher endogenous Trx levels (Figure 2D). However, neither Trx silencing nor Trx overexpression affected Jab1 levels. Thus, our findings indicate that Jab1 is an upstream regulator and positively controls Trx expression in AML-M5 cells. To further delineate whether Jab1 regulates transcriptionally Trx, we performed a luciferase reporter assays with the human Trx promoter. Our data demonstrated that transactivation of Trx expression is driven by Jab1 through the AP-1 binding site (Figure 2E-H). In conclusion, these results elucidate a novel Jab1 and Trx axis, which is a critical cellular process in the pathobiology of AML-M5 and could promotes AML-M5 relapse. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Manganese Oxide-Based Chemically Powered Micromotors.

Chemically powered micromotors represent an exciting research area in nanotechnology. Such artificial devices are typically driven by catalytic bubble formation, taking place at the solid-liquid interface. Platinum has been most frequently used for the fabrication of different micromotors due to its superior catalytic efficiency. Other materials typically suffer from slow speeds and require very high concentrations of chemical fuel. Here, we report preparation and characterization of fast moving micromotors based on manganese oxide (MnO2) with different geometrical shapes (tubes, rods, and spheres). On the basis of the results, the prepared micromotors reached the highest speeds (up to ∼900 μm s(-1) in 10% H2O2) reported to date for any MnO2-based micromotors. Moreover, they moved by bubble propulsion even at very low concentrations of peroxide fuel. Thus, MnO2 represents a promising material for the preparation of micromotors for various biomedical or environmental applications, where high speeds are desired.

New Nanomaterials and Luminescent Optical Sensors for Detection of Hydrogen Peroxide

Accurate methods that can continuously detect low concentrations of hydrogen peroxide (H2O2) have a huge application potential in biological, pharmaceutical, clinical and environmental analysis. Luminescent probes and nanomaterials are used for fabrication of sensors for H2O2 that can be applied for these purposes. In contrast to previous reviews focusing on the chemical design of molecular probes for H2O2, this mini-review highlights the latest luminescent nanoparticular materials and new luminescent optical sensors for H2O2 in terms of the nanomaterial composition and luminescent receptor used in the sensors. The nanomaterial section is subdivided into schemes based on gold nanoparticles, polymeric nanoparticles with embedded enzymes, probes showing aggregation-induced emission enhancement, quantum dots, lanthanide-based nanoparticles and carbon based nanomaterials, respectively. Moreover, the sensors are ordered according to the type of luminescent receptor used within the sensor membranes. Among them are lanthanide complexes, metal-ligand complexes, oxidic nanoparticles and organic dyes. Further, the optical sensors are confined to those that are capable to monitor the concentration of H2O2 in a sample over time or are reusable. Optical sensors responding to gaseous H2O2 are not covered. All nanomaterials and sensors are characterized with respect to the analytical reaction towards H2O2, limit of detection (LOD), analytical range, electrolyte, pH and response time/incubation time. Applications to real samples are given. Finally, we assess the suitability of the nanomaterials to be used in membrane-based sensors and discuss future trends and perspectives of these sensors in biomedical research.

Microbial Attachment Inhibition through Low-Voltage Electrochemical Reactions on Electrically Conducting Membranes.

Bacterial biofilm formation on membrane surfaces remains a serious challenge in water treatment systems. The impact of low voltages on microbial attachment to electrically conducting ultrafiltration membranes was investigated using a direct observation cross-flow membrane system mounted on a fluorescence microscope. Escherichia coli and microparticle deposition and detachment rates were measured as a function of the applied electrical potential to the membrane surface. Selecting bacteria and particles with low surface charge minimized electrostatic interactions between the bacteria and charged membrane surface. Application of an electrical potential had a significant impact on the detachment of live bacteria in comparison to dead bacteria and particles. Image analysis indicated that when a potential of 1.5 V was applied to the membrane/counter electrode pair, the percent of dead bacteria was 32±2.1 and 67±3.6% when the membrane was used as a cathode or anode, respectively, while at a potential of 1 V, 92±2.4% were alive. The application of low electrical potentials resulted in the production of low (μM) concentrations of hydrogen peroxide (HP) through the electroreduction of oxygen. The electrochemically produced HP reduced microbial cell viability and increased cellular permeability. Exposure to low concentrations of electrochemically produced HP on the membrane surface prevents bacterial attachment, thus ensuring biofilm-free conditions during membrane filtration operations.

Electrochemical scaffold generates localized, low concentration of hydrogen peroxide that inhibits bacterial pathogens and biofilms.

We hypothesized that low concentrations of H2O2 could be generated through the electrochemical conversion of oxygen by applying an electric potential to a conductive scaffold and produce a low, but constant, concentration of H2O2 that would be sufficient to destroy biofilms. To test our hypothesis we used a multidrug-resistant Acinetobacter baumannii strain, because this species is often implicated in difficult-to-treat biofilm infections. We used conductive carbon fabric as the scaffold material (“e-scaffold”). In vitro experiments demonstrated the production of a maximum constant concentration of ~25 μM H2O2 near the e-scaffold surface. An e-scaffold was overlaid onto an existing A. baumannii biofilm, and within 24 h there was a ~4-log reduction in viable bacteria with an ~80% decrease in biofilm surface coverage. A similar procedure was used to overlay an e-scaffold onto an existing A. baumannii biofilm that was grown on a porcine explant. After 24 h, there was a ~3-log reduction in viable bacteria from the infected porcine explants with no observable damage to the underlying mammalian tissue based on a viability assay and histology. This research establishes a novel foundation for an alternative antibiotic-free wound dressing to eliminate biofilms.

Enamel Surface Changes After Exposure to Bleaching Gels Containing Carbamide Peroxide or Hydrogen Peroxide.

This study evaluated the differences in enamel color change, surface hardness, elastic modulus, and surface roughness between treatments with four bleaching gels containing carbamide peroxide (two at 10% and one each at 35%, and 45%) and two bleaching gels containing hydrogen peroxide (two at 40%). Enamel specimens were bleached and color changes were measured. Color change was calculated using either ΔE or the Bleaching Index (BI). Then, surface hardness, elastic modulus, and surface roughness of the enamel specimens were evaluated. All measurements were performed at baseline and directly after the first bleaching treatment for all carbamide peroxide- and hydrogen peroxide-containing bleaching gels. In addition, final measurements were made 24 hours after each of a total of 10 bleaching treatments for carbamide peroxide bleaching gels, and 1 week after each of a total of three bleaching treatments for hydrogen peroxide bleaching gels. After the last bleaching treatment, respective ΔE scores were 17.6 and 8.2 for the two 10% carbamide peroxide gels, 12.9 and 5.6 for the 45% and 35% carbamide peroxide gels, and 9.6 and 13.9 for the two 40% hydrogen peroxide gels. The respective BI scores were -2.0 and -2.0 for the two 10% carbamide peroxide gels, -3.5 and -1.5 for the 45% and 35% carbamide peroxide gels, and -2.0 and -3.0 for the two 40% hydrogen peroxide gels. Each bleaching gel treatment resulted in significant whitening; however, no significant difference was found among the gels after the last bleaching. Whitening occurred within the first bleaching treatments and did not increase significantly during the remaining treatments. Surface hardness significantly decreased after the last bleaching treatment, when 10% carbamide peroxide was used. Furthermore, significant changes in the elastic modulus or surface roughness occurred only after treatment with 10% carbamide peroxide. All six bleaching gels effectively bleached the enamel specimens independent of their concentration of peroxide. Gels with low peroxide concentration and longer contact time negatively affected the enamel surface.

Low Concentrations of Hydrogen Peroxide Activate the Antioxidant Defense System in Human Sperm Cells.

The effect of low concentrations of hydrogen peroxide (10-100µM) on sperm motility and on the activity of the sperm enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDS) was investigated. Incubation of semen samples with 10 and 100 µM hydrogen peroxide increased the content of spermatozoa with progressive motility by 20 and 18%, respectively, and enhanced the activity of GAPDS in the sperm cells by 27 and 20% compared to a semen sample incubated without additions. It was also found that incubation with 10 µM hydrogen peroxide increased the content of reduced glutathione (GSH) in sperm cells by 50% on average compared to that in the control samples. It is supposed that low concentrations of hydrogen peroxide activate the pentose phosphate pathway, resulting in NADPH synthesis and the reduction of the oxidized glutathione by glutathione reductase yielding GSH. The formed GSH reduces the oxidized cysteine residues of the GAPDS active site, increasing the activity of the enzyme, which in turn enhances the content of sperm cells with progressive motility. Thus, the increase in motile spermatozoa in the presence of low concentrations of hydrogen peroxide can serve as an indicator of normal functioning of the antioxidant defense system in sperm cells.

Disinfection by hydrogen peroxide nebulization increases susceptibility to avian pathogenic Escherichia coli.

BackgroundAvian pathogenic Escherichia coli (APEC) are the major cause of economic losses in the poultry industry worldwide. Traditionally, antibiotics are used to treat and prevent colibacillosis in broilers. Due to resistance development other ways of preventing/treating the disease have to be found. Therefore during this study the nebulization of low concentrations of hydrogen peroxide (H2O2) was tested in the presence of chickens to lower pathogenicity of APEC.ResultsSignificantly higher total lesion scores and higher E. coli concentrations were found in the spleen of chickens exposed to 2 % H2O2 compared to those exposed to 1 % H2O2 and control chickens which had been exposed to nebulization with distilled water. Higher total lesions scores and E. coli concentrations in the spleen were found in chickens exposed to 1 % H2O2 in comparison to control chickens (not significant).ConclusionH2O2 is rendering animals more prone to APEC infection contraindicating H2O2 nebulization in the presence of chickens.

Clinical efficacy of a bleaching enzyme-based toothpaste. A double-blind controlled clinical trial

ObjectivesTo assess the efficacy of a bleaching enzyme-based toothpaste. Material and methodsA randomized clinical trial was carried out, comprising 48 participants with teeth exhibiting color A3 or higher according to the Vita Classical guide. One-half of the sample received the bleaching enzyme-based toothpaste (White Kin®), while the other received placebo toothpaste. Both products were supplied in identical containers and had the same composition except for the active components. The teeth color was measured with a spectrophotometer. The patients were instructed to brush their teeth three times a day during 3min with the assigned product, during 12 weeks. The color measurements were repeated after 3, 6, 9 and 12 weeks of treatment. Color variation was based on the CIE L*a*b* coordinates, ΔE and the EW index. The relationship of these variables at different observation times were performed using a generalized estimating equations model, which evaluated the effect of treatment, time and interaction. ResultsThe patients using the bleaching enzyme-based toothpaste showed an increase in lightness (80.14 -treatment- versus 79.25 -control group-) and a reduction in component b*. ΔE was found higher in the treatment group (p=0.064), close to statistical significance. ConclusionsThe bleaching enzyme-based toothpaste could be potentially efficient in the modification in tooth color progressing from the third to ninth week of treatment, tending to stabilize after the ninth week. Clinical relevanceA very low carbamide peroxide concentration, with the incorporation of lactoperoxidase, tooth paste, tends to offer clinically satisfactory results, in terms of modifications in tooth color, nevertheless no significant differences were founded when compared to the control group, with an oral hygiene controlled along the study.