Peroxide Concentration Research Articles

In Vitro Evaluation of the Effectiveness and pH Variation of Dental Bleaching Gels and Their Effect on Enamel Surface Roughness

Objectives: Potential adverse effects and pH-related effectiveness of bleaching agents have raised some concerns. The aim of this study was to compare three bleaching agents containing hydrogen peroxide (HP) and carbamide peroxide (CP) in terms of whitening effectiveness, pH variation, and changes in enamel surface roughness. Methods: After controlled staining with a black tea solution, 42 human enamel specimens underwent bleaching treatment using the following agents: HP 40%; HP 35%; CP 16%. Color changes were evaluated according to the CIEDE2000 system. Gel pH was measured before and after each application. Surface roughness (Sa) was assessed through optical 3D profilometry before and after bleaching treatment. Results: The whitening effectiveness was similar for HP 40% and HP 35% while CP 16% had significantly lower results. HP 40% showed a remarkable pH acidification (−0.41), while HP 35% and CP 16% showed a mild increase in pH values (+0.26 and +0.03, respectively), and the differences between HP 40% and HP 35% and between HP 35% and CP 16% were statistically significant. Sa slightly decreased in all groups after bleaching, with no significant differences among them and a significant difference in HP 40% before and after treatment. Conclusions: Similar bleaching results were achieved regardless of pH and HP concentration for HP-based agents, while a lower bleaching effect was observed for the less concentrated CP-based agent, as anticipated. Higher HP and greater tendency to pH instability induced more pronounced modifications of surface roughness. This in vitro study suggests that bleaching gels with neutral and stable pH ensure good bleaching effectiveness and are less likely to cause enamel surface changes.

Genetically Encoded Biosensor HyPer as a Tool for Quantification of Intracellular Hydrogen Peroxide Concentrations

This mini-reviewsystematizes information on methods for quantitative assessment of intracellular hydrogenperoxide concentration based on the use of a genetically encodedperoxide sensor HyPer. Two approaches are being considered: 1) calibrationof the biosensor using exogenous hydrogen peroxide, based on assessingthe rate of peroxide penetration into cells and intracellular peroxidaseactivity; 2) direct determination of the intracellular peroxide content, basedon measuring the level of oxidation of the biosensor, theoxidation reaction constant and the reduction reaction constant of HyPerin the cells. The use of these methods makes itpossible to solve a wide range of tasks in cellularredox biology—to determine the range of physiological anddamaging concentrations of hydrogen peroxide in cells, to evaluate theeffectiveness of the antioxidant defense system in various cellular compartmentsunder conditions of oxidative stress, to determine the contribution ofvarious enzymatic systems to the peroxidase activity of cells, andto characterize antioxidant defense systems in various biological contexts (inthe process of cellular senescence, differentiation, reprogramming, during the developmentof pathologies). The described methods can be adapted for othergenetically encoded hydrogen peroxide biosensors.

Pseudomonas oryzihabitans D1-104/3 and P. gessardii C31-106/3 differentially modulate the antioxidative response of duckweed (Lemna minor L.) to salt stress

IntroductionThe common duckweed (L. minor) is a model organism for investigation of plant physiology, especially stress-related responses. Its two physiological characteristics are of special interest: (1) salt-stressed duckweeds may accumulate starch, a precursor for biofuel; (2) duckweeds are associated with various beneficial (plant-growth promoting, PGP) bacterial strains. In this paper, we analyzed the role of two bacterial strains: Pseudomonas oryzihabitans D1-104/3 and P. gessardii C31-106/3 in regulation of duckweed's growth and antioxidative responses to salt (10 and 100 mM NaCl) and hypothesized that they alleviate salt-induced oxidative stress.MethodsFresh and dry weight, frond number, photosynthetic pigments, malondialdehyde (MDA) and hydrogen peroxide (H2O2), ascorbic acid (AsA), proline, total polyphenol (TPC) and starch content, as well as antioxidant capacity and antioxidant enzymatic activity were measured after 14 days. Fluorescence microscopy was used to visualize bacterial presence on duckweeds.ResultsFluorescence microscope revealed that Pseudomonas bacteria colonized all duckweed surfaces. The doubling time of duckweeds inoculated with P. gessardii C31-106/3 was significantly longer. Additionally, at 0 and 10 mM NaCl, this strain decreased chlorosis in duckweeds. Moreover, P. gessardii C31-106/3 increased dry-to-fresh-weight ratio, proline, chlorophyll a, b and carotenoid content at 100 mM, as well as AsA content in plants in NaCl-free medium, while P. oryzihabitans D1-104/3 increased AsA at 100 mM NaCl. Both bacterial strains decreased lipid peroxidation, while P. gessardii C31-106/3 increased and P. oryzihabitans D1-104/3 decreased H2O2 content at 100 mM and 0 mM NaCl, respectively. Bacteria significantly increased TPC and antioxidant capacity at 100 mM NaCl, particularly P. oryzihabitans D1-104/3. After 14 days, the SOD and POX activities were at the same level in all samples. At 100 mM NaCl, CAT activity was increased in all plants.DiscussionThe results of this study show that two Pseudomonas strains had markedly different effects on duckweed: while P. oryzihabitans D1-104/3 supported growth, P. gessardii C31-106/3 prioritized salt stress tolerance in duckweeds.

Methodological optimization for efficient degradation of Acid Violet 49 using advanced oxidation processes and varied photocatalyst combinations

This study investigates the photodegradation of Acid Violet 49 in an aqueous medium under UV, UV/H2O2, and combined with photo catalyst (UV/H2O2/TiO2, UV/H2O2/ZnO, and UV/H2O2/SnO2). The impact of all operational parameters including catalytic dosage, peroxidation (H2O2), pH and dye concentration were evaluated. The degradation efficiency of AV49 was enhanced up to 96% with the alternative photocatalyst UV/H2O2/ZnO under the circumstances of 0.6mL H2O2, 0.9 g ZnO, 50 mg/L initial dye concentration, and pH 9 after 90 min. Hemolytic test were used to check the toxicity level of products. FTIR spectroscopy of UV/ZnO/H2O2 was applied to identify the functional group of AV49 before and end product of the degradation. Moreover, the analytical technique LC-MS provided valuable information regarding the degradation products of AV 49. A proposed pathway was identified based on the findings of the degradation product.

Macromolecular crowding and bicarbonate enhance the hydrogen peroxide-induced inactivation of glyceraldehyde-3-phosphate dehydrogenase.

The active site Cys residue in glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is sensitive to oxidation by hydrogen peroxide (H2O2), with this resulting in enzyme inactivation. This re-routes the carbon flux from glycolysis to the pentose phosphate pathway favoring the formation of NADPH and synthetic intermediates required for antioxidant defense and repair systems. Consequently, GAPDH inactivation serves as a redox switch for metabolic adaptation under conditions of oxidative stress. However, there is a major knowledge gap as to how GAPDH is efficiently oxidized and inactivated, when the increase in intracellular H2O2 is modest, and there is a high concentration of alternative (non-signaling) thiols and efficient peroxide removing systems. We have therefore explored whether GAPDH inactivation is enhanced by two factors of in vivo relevance: macromolecular crowding, an inherent property of biological environments, and the presence of bicarbonate, an abundant biological buffer. Bicarbonate is already known to modulate H2O2 metabolism via formation of peroxymonocarbonate. GAPDH activity was assessed in experiments with low doses of H2O2 under both dilute and crowded conditions (induced by inert high molecular mass polymers and small molecules), in both the absence and presence of 25 mM sodium bicarbonate. H2O2-induced inactivation of GAPDH was observed to be significantly enhanced under macromolecular crowding conditions, with bicarbonate having an additional effect. These data strongly suggest that these two factors are of major importance in redox switch mechanisms involving GAPDH (and possibly other thiol-dependent systems) within the cellular environment.

Improvement of maize drought tolerance by foliar application of zinc selenide quantum dots

Maize (Zea mays L.) is an important cereal crop grown in arid and semiarid regions of the world. During the reproductive phase, it is more frequently exposed to drought stress, resulting in lower grain yield due to oxidative damage. Selenium and zinc oxide nanoparticles possess inherent antioxidant properties that can alleviate drought-induced oxidative stress by the catalytic scavenging of reactive oxygen species, thereby protecting maize photosynthesis and grain yield. However, the effect of zinc selenide quantum dots (ZnSe QDs) under drought stress was not been quantified. Hence, the aim of this study was to quantify the (i) toxicity potential of ZnSe QDs and (ii) drought mitigation potential of ZnSe QDs by assessing the transpiration rate, photosynthetic rate, oxidant production, antioxidant enzyme activity and seed yield of maize under limited soil moisture levels. Toxicity experiments were carried out with 0 mg L−1 to 500 mg L−1 of ZnSe QDs on earthworms and azolla. The results showed that up to 20 mg L−1, the growth rates of earthworms and azolla were not affected. The dry-down experiment was conducted with three treatments: foliar spray of (i) water, (ii) ZnSe QDs (20 mg L−1), and (iii) combined zinc sulfate (10 mg L−1) and sodium selenate (10 mg L−1). ZnSe or Se applications under drying soil reduced the transpiration rate compared to water spray by partially closing the stomata. ZnSe application at 20 mg L−1 at the tasselling stage significantly increased the photosynthetic rate (25%) by increasing catalase (98%) and peroxidase (85%) enzyme activity and decreased the hydrogen peroxide (23%) content compared to water spray, indicating that premature leaf senescence was delayed under rainfed conditions. ZnSe spray increased seed yield (26%) over water spray by increasing the number of seeds cob-1 (42%). The study concluded that foliar application of ZnSe (20 mg L−1) could decrease drought-induced effects in maize.

Influence of Chlorella vulgaris and Pediastrum boryanum extracts carried on nanocellulose on the immune response of Biomphalaria alexandrina snails against Schistosoma mansoni infection.

Continuous efforts are made to explore alternative methods for reducing Schistosomiasis. So, this study evaluated the effectiveness of Chlorella vulgaris and Pediastrum boryanum extracts carried on their nanocrystalline cellulose (NCC) as immunostimulants for Biomphalaria alexandrina snails against Schistosoma mansoni infection. The results showed that the lowest cercarial shedding/snail was 340 and 330 with 400 mg/L of C. vulgaris extract and NCC + C. vulgaris extract, respectively. Meanwhile, it was decreased with 200 mg/L of P. boryanum extract and 400 mg/L of NCC + P. boryanum extract, with high survival rates for all treatments. In addition, snails treated with 400 mg/L of C. vulgaris extract and 200 and 400 mg/L of NCC + C. vulgaris extract showed a significant decrease in the contents of hydrogen peroxide (0.639, 0.426, and 0.564 mM/L), respectively, compared to the control group (0.695 mM/L). Furthermore, C. vulgaris extracts induced numerous hemocytes around immature cercariae and sporocysts. P. boryanum extracts showed degenerated sporocysts surrounded by plenty of hemocytes. Nanocellulose carriers improved the delivery of microalgal components within B. alexandrina snails, causing the cercariae to lose their ideal shape. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that C. vulgaris and P. boryanum extracts contained oleic acid, which improved the immunological response of snails, and glutamic acid and flavonoids acted as immune modulators and antioxidants. Ultimately, the toxicity assay indicated that NCC + C. vulgaris extract and NCC + P. boryanum extract were the safest for Artemia salina as a non-target aquatic organism.

Drought-mediated oxidative stress and its scavenging differ between citrus hybrids with medium and late fruit maturation

Drought stress is a major environmental factor limiting citrus productivity. Still, differences in drought sensitivity between citrus hybrids of different maturation periods have so far not been reported. Here, we selected a medium-maturing (Fertile orange: FO (Citrus reticulata cv. Fertile orange) and a late-maturing citrus hybrid (Newhall Navel orange: NO (Citrus sinensis Osbeck cv. Newhall) and determined the physiological and biochemical traits of leaves, roots, wood and bark. Our results showed that drought significantly decreased net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of citrus leaves. Oxidative stress upon drought was indicated by enhanced foliar malondialdehyde (MDA) and hydrogen peroxide contents, as well as a stimulation of the anti-oxidative system. This stimulation included the contents of dehydroascorbic acid (DHA), glutathione (GSH) and oxidized glutathione (GSSG) in leaves, roots, wood and bark, as well as activities of antioxidative enzymes of glutathione reductase (GR), dehydroascorbate reductase (DHAR), superoxide dismutase (SOD) and peroxidase (POD). The late maturing NO hybrid not only showed better general physiological performance as indicated by increased Pn in leaves, but also higher biochemical ROS scavenging and osmotic capacity as indicated by increased ascorbic acids (ASA), DHA, and proline contents, as well as activities of enzymes of SOD, POD, ASA/DHA and GSH/GSSG ratios in the investigated tissues compared to the FO hybrid under drought and control conditions. Analysis of molecular mechanisms of signaling, regulatory and functional genes expression are suggested for future studies to elucidate the complex interplay of molecular, biochemical and physiological responses of citrus hybrids to drought.

Cyano-modified Potassium-Sodium Poly(Heptazine Imide) Nanosheets for Photocatalytic Hydrogen Peroxide Reduction Coupled with 5-hydroxymethylfurfural Oxidation

The efficacy of poly(heptazinonimide) (PHI) materials in photocatalytic applications is often constrained by limited visible light absorption and charge separation. In this study, we successfully synthesized cyano-modified potassium-sodium poly(heptazinonimide) (KNPHI) nanosheets using a molten salt method, which significantly enhances photocatalytic performance. The resulting KNPHI nanosheets achieve hydrogen peroxide (H₂O₂) concentrations up to 8.64mM, nearly 1.9 and 123 times greater than that achieved by KPHI and PCN respectively. Notably, integrating cyano groups and potassium-sodium ions within KNPHI enhances visible light absorption, intermediate adsorption and charge separation, as confirmed by experimental characterizations and DFT calculations, thereby improving the oxygen reduction reaction efficiency. Furthermore, the use of KNPHI for 5-hydroxymethylfurfural oxidation, coupled with oxygen reduction reaction pathway, was systematically investigated. These findings offer promising avenues for the development of advanced photocatalysts that support sustainable energy production and green chemical synthesis.

Characterization of the chitinase gene family in Saccharum reveals the disease resistance mechanism of ScChiVII1.

A chitinase gene ScChiVII1 which is involved in defense against pathogen stress was characterized in sugarcane. Chitinases, a subclass of pathogenesis-related proteins, catalyze chitin hydrolysis and play a key role in plant defense against chitin-containing pathogens. However, there is little research on disease resistance analysis of chitinase genes in sugarcane, and the systematic identification of their gene families has not been reported. In this study, 85 SsChi and 23 ShChi genes, which were divided into 6 groups, were identified from the wild sugarcane species Saccharum spontaneum and Saccharum hybrid cultivar R570, respectively. Transcriptome analysis and real-time quantitative PCR revealed that SsChi genes responded to smut pathogen stress. The chitinase crude extracted from the leaves of transgenic Nicotiana benthamiana plants overexpressing ScChiVII1 (a homologous gene of SsChi22a) inhibited the hyphal growth of Fusarium solani var. coeruleum and Sporisorium scitamineum. Notably, the chitinase and catalase activities and the jasmonic acid content in the leaves of ScChiVII1 transgenic N. benthamiana increased after inoculation with F solani var. coeruleum, but the salicylic acid, hydrogen peroxide, and malondialdehyde contents decreased. Comprehensive RNA sequencing of leaves before (0day) and after inoculation (2days) revealed that ScChiVII1 transgenic tobacco enhanced plant disease resistance by activating transcription factors and disease resistance-related signaling pathways, and modulating the expression of genes involved in the hypersensitive response and ethylene synthesis pathways. Taken together, this study provides comprehensive information on the chitinase gene family and offers potential genetic resources for disease resistance breeding in sugarcane.

Sustainable Protocols For Leaf Sample Collection in In-Vitro Culture: Evaluating The Impact of Sample Bags and Hydrogen Peroxide Pre-Sterilization

This study investigates sustainable leaf sample collection protocols for in-vitro culture (IVC) of chili (Capsicum frutescens) and tomato (Solanum lycopersicum) leaves. The research aimed to enhance viability and reduce contamination of leaf explants by evaluating various types of sample bags and different concentrations of hydrogen peroxide (H2O2) pre-sterilization. Specifically, the study compared the effectiveness of normal sealed (NS) bags and vacuum-sealed (VS) bags, including high-action (VSH) and low-action (VSL) vacuum-sealed bags, alongside H2O2 pre-sterilization at various concentrations. Leaf samples were treated with ten different concentrations of H2O2 (5% to 50%) to assess their impact on necrosis and surface contamination over 72 hr. Results showed that higher H2O2 concentrations (above 30%) caused significant necrosis, while concentrations between 10% and 15% provided optimal pre-sterilization for both leaf types, effectively reducing contamination without excessive tissue damage. In the second phase, the research examined the influence of different sample bags on leaf explant sustainability. Vacuum-sealed bags, particularly those with low-action vacuum (VSL), significantly improved leaf longevity and minimized contaminant emergence compared to normal sealed bags. Combined with 15% H2O2 pre-sterilization, VSL bags performed best, maintaining leaf morphology and viability for extended periods. Statistical analyses confirmed the significant impact of sampling bag type and pre-sterilization on contamination levels, necrosis emergence, and leaf longevity. The findings suggest that using low-action vacuum-sealed bags (VSL) with 15% H2O2 pre-sterilization is a promising approach for sustainable leaf sample collection, enhancing the success rate of IVC by minimizing microbial contamination and preserving leaf integrity during transport. This optimized protocol offers valuable insights for researchers and practitioners in plant tissue culture and agriculture, aiming to improve the sustainability and efficiency of leaf sample collection for in-vitro applications.

INDIGO BLUE DEGRADATION: PROBABLE PRESENCE OF DYE ADSORBED BY IRON HYDROXIDE DURING FENTON PROCESS

A chemical method using FeSO4 and H2O2 was selected for indigo blue (IB) degradation in aqueous medium. The initial experiments demonstrated that high concentrations of hydrogen peroxide (H2O2) and iron sulfate heptahydrate (FeSO4.7H2O) were capable of total degradation of IB (approximately 100%). Controlled tests, varying the concentrations of both reagents, revealed that the mixture containing approximately 350 mg/L (v/v) of FeSO4.7H2O and 0.57% (v/v) of H2O2wasconsiderablyefficient in the degradation of IB (1,000 mg/L). The decay kinetics revealed rapid IB degradation and possible IB adsorption on iron (III) hydroxide precipitate [Fe(OH)3]↓. However, the adsorbed IB also subsequently, leaves the residue of [Fe(OH)3]↓, which suggests the occurrence of not only chemical degradation of IB but also its possible adsorption by Fe(OH)3 precipitate.

Improving plant growth, anthocyanin production and oxidative status of red lettuce (Lactuca sativa cv. Lolla Rossa) by optimizing red to blue light ratio with a constant green light fraction in a plant factory

Previous studies have reported contrasting effects of light quality on plant growth and anthocyanin content in lettuce leaves. This study aimed to optimize the red-to-blue light ratio with a constant green light fraction to improve biomass and anthocyanin production in red lettuce (Lactuca sativa cv. ‘Lolla Rossa’) in a plant Factory. Six treatments with varying proportions of red (R, 660 nm) and blue (B, 450 nm), along with a constant fraction of green (G, 540 nm) light, recorded as R125:B25:G50, R120:B30:G50, R112:B37:G50, R100:B50:G50, R75:B75:G50, and R50:B100:G50 were set up in this study. The total photosynthetic photon flux density for all treatments was 200 μmol m−2s−1 with a green light intensity of 50 μmol m−2s−1. The results showed that, compared with treatment R50:B100:G50, the fresh and dry weights, leaf length, leaf area and stem width of lettuce plants under treatment R125:B25:G50 showed an increase of 73.4 %, 47.8 %, 35.5 %, 54.9 %, and 58.3 %, respectively. Additionally, red light was found to promote increased weight of lettuce plant roots. Further, the anthocyanin content, nitrate content, and stomata density under treatment R50:B100:G50 were 6.75, 1.5, and 1.42 times higher than those under treatment R125:B25:G50. Enzymatic activities such as hydrogen peroxide (H2O2), superoxide dismutase (SOD), ascorbic acid (AsA), and anthocyanin concentration per fresh weight of plant were higher under treatment R100:B50:G50, comparing with those under treatment R125:B25:G50. The above results indicate that a higher red-to-blue light ratio enhances plant biomass, photosynthesis, and certain nutrients, while increasing the blue ratio promotes anthocyanin accumulation and antioxidants, protecting cells from oxidative stress. Based on this analysis, treatment R100:B50:G50 can be considered as the suitable light spectrum for optimal growth, anthocyanin accumulation and antioxidant activity of lettuce plants. Further researches are needed to explain these effects and refine lighting methods for optimal lettuce production and nutritional quality.

Effect of an experimental desensitizer with a hydroxyapatite-capsaicin composite applied before in-office dental bleaching on hydrogen peroxide diffusion, color and surface changes.

To evaluate a prior application of an experimental desensitizer containing a hydroxyapatite-capsaicin composite (HAp-CAP) in different concentrations on hydrogen peroxide (HP) diffusion into the pulp chamber, bleaching efficacy (BE) and on physical and chemical alterations of the enamel surface after in-office bleaching. Forty sound premolars were randomized in five groups according to each experimental condition (n = 8): no bleaching (negative control), only bleaching (positive control), 0.1%, 1% and 5% of HAp-CAP. Four groups were submitted to in-office bleaching (HP 35%) post-desensitizer application. The HP concentration (µg/mL) on the pulp chamber was measured by UV-Vis spectrophotometer. The BE was measured by digital spectrophotometer (ΔEab, ΔE00 and ΔWID) before and after 7 days bleaching. Enamel tooth fragments obtained from twenty molars were submitted to the same experimental conditions and analyzed using FE-SEM and EDS, Vickers microhardness (VHN), Raman spectroscopy, and nanoroughness (Ra) by AFM to evaluate morphologic and chemical changes on enamel surface. All data were submitted to statistical analysis (α = 0.05). The groups treated with HAp-CAP exhibited a lower concentration of HP in the pulp chamber compared to only bleaching group (p < 0.05). There were no significant differences observed in BE between HAp-CAP groups and only bleaching group (p > 0.05). Only HAp-CAP 5% showed no significant differences in VHN values when compared to no bleaching group (p > 0.05). There were no significant differences among any group in Ra values (p > 0.05). The groups submitted to HAp-CAP showed a higher mineral concentration when compared to only bleaching group (p < 0.05). Desensitizers containing HAp-CAP up to 5% effectively reduce HP diffusion into the pulp chamber after in-office bleaching, without interfering to BE and Ra, as well as prevent enamel demineralization. The use of desensitizers containing HAp-CAP during in-office bleaching treatments offers a promising approach to reduce the risk of pulp irritation caused by hydrogen peroxide diffusion, without compromising the bleaching effectiveness or causing surface roughness.

Improving bleachability of thermomechanical pulp by ozone–hydrogen peroxide system

Thermomechanical pulp (TMP) was bleached with an ozone–hydrogen peroxide system, with the addition of hydrogen peroxide and ethylene glycol to enhance bleaching efficacy. The ISO brightness of TMP increased proportionally with higher concentrations of hydrogen peroxide across all sequences. Notably, TMP treated with the ozone and hydrogen peroxide sequence (ZP sequence) exhibited ISO brightness levels comparable to those of TMP bleached with hydrogen peroxide alone. However, the addition of hydrogen peroxide during the Z stage of the pZP sequence resulted in a 2.4% increase in ISO brightness and enhanced lignin solubility. A brief alkaline extraction step in the pZEP sequence led to a significant 4.3% increase in ISO brightness, though this improvement was accompanied by a yield loss due to removal of lignin in the E stage. Furthermore, the addition of polyethylene glycol alleviated yield loss by enhancing the selectivity of ozone bleaching, while effectively maintaining a stable ISO brightness.

Green synthesis of TiO₂ phases for efficient photocatalytic degradation of oxytetracycline in real aquaculture wastewater

The increasing use of antibiotics, particularly oxytetracycline (OTC), in aquaculture has raised concerns about environmental pollution and the spread of antibiotic-resistant bacteria. This study investigates the photocatalytic removal of OTC in real aquaculture wastewater using green-synthesized titanium dioxide (TiO₂) derived from Neem leaves. Three phases of TiO₂ were successfully synthesized, namely anatase, rutile, and brookite, with their properties evaluated using XRD, FESEM, photocurrent response, EIS, and photoluminescence. Among the phases studied, Neem-Anatase TiO2 demonstrated superior performance, achieving 86.63 % ± 2.7 % antibiotic degradation in pure OTC aqueous solution. With a band gap of 3.15 eV, Neem-Anatase TiO₂ exhibited light absorption capability 1.5 and 6 times greater than Neem-rutile (3.4 eV) and Neem-brookite (3.71 eV), respectively. Neem-Anatase TiO₂ maintained a 69.3 % ± 1.2 % degradation efficiency over four recycling cycles, and hole radicals was determined as the primary radical species involved in the photocatalytic process. In real aquaculture water, the Neem-Anatase TiO2 OTC degradation performance could achieve 69.63 % ± 3.4 % after optimizing experimental parameters including the initial Neem-Anatase TiO2 dosage (0.6 mg/mL), initial OTC concentration (10 ppm), pH (pH 6) and hydrogen peroxide concentration (5 mM) using the Design Expert software. Factors contributing to the reduction of OTC removal efficiency in aquaculture water include the screening and scavenging effect by the dissolved solids, organic and inorganic components in the water. This work demonstrates the potential of green-synthesized TiO₂, particularly the anatase phase, as a sustainable solution for antibiotic pollution in aquaculture wastewater thereby mitigating environmental impacts and limiting antibiotic resistance in aquatic ecosystems.

Small Extracellular Vesicle-Associated MiRNAs in Polarized Retinal Pigmented Epithelium.

Oxidative stress in the retinal pigmented epithelium (RPE) has been implicated in age-related macular degeneration by impacting endocytic trafficking, including the formation, content, and secretion of extracellular vesicles (EVs). Using our model of polarized primary porcine RPE (pRPE) cells under chronic subtoxic oxidative stress, we tested the hypothesis that RPE miRNAs packaged into EVs are secreted in a polarized manner and contribute to maintaining RPE homeostasis. Small EVs (sEVs) enriched for exosomes were isolated from apical and basal conditioned media from pRPE cells grown for up to four weeks with or without low concentrations of hydrogen peroxide using two sEV isolation methods, leading to eight experimental groups. The sEV miRNA expression was profiled using miRNA-Seq with Illumina MiSeq, followed by quality control and bioinformatics analysis for differential expression using the R computing environment. Expression of selected miRNAs were validated using qRT-PCR. We identified miRNA content differences carried by sEVs isolated using two ultracentrifugation-based methods. Regardless of the sEV isolation method, miR-182 and miR-183 were enriched in the cargo of apically secreted sEVs, and miR-122 in the cargo of basally secreted sEVs from RPE cells during normal homeostatic conditions. After oxidative stress, miR-183 levels were significantly decreased in the cargo of apically released sEVs from stressed RPE cells. We curated RPE sEV miRNA datasets based on cell polarity and oxidative stress. Unbiased miRNA analysis identified differences based on polarity, stress, and sEV isolation methods. These findings suggest that miRNAs in sEVs may contribute to RPE homeostasis and function in a polarized manner.

Degradation of synthetic reactive Pyrazole-133 dye by using an advanced oxidation process assisted by gamma radiations

This study investigated the degradation of the reactive dye RP-133 in aqueous solution using various hydrogen peroxide concentrations and gamma radiation doses (1–20 kGy). The solution's initial dye concentration and pH were optimized for the most effective degradation efficiency. The dye was treated with H2O2 and gamma radiation separately. At an acidic pH, an absorbed dose of 20 kGy, and 0.9 mL of H2O2, a 95% decomposition rate was achieved. FTIR analysis revealed differences in the functional groups of treated and untreated dye. Intermediates formed during degradation were identified using GC-MS. Hemolytic and Ames tests assessed the cytotoxicity and mutagenicity of the dye. Gamma radiation treatment significantly reduced both mutagenicity and cytotoxicity. Cytotoxicity decreased from 15.1% to 7.6%, and mutagenicity of bacterial strains TA98 and TA100 was reduced by 81.3% and 82.3%, respectively. The formation of low-molecular-weight organic acids further oxidized to carbon dioxide and water, indicating the efficiency of the advanced oxidation process. Combining gamma radiation with H2O2 effectively degraded RP-133, reducing its cytotoxicity and mutagenicity.

Effect of Fenton-Based Processes on Arsenic Removal in the Presence of Humic Acid

Geogenic arsenic (As) contamination in groundwater poses a significant public health risk in many regions worldwide. Previous studies have reported hydrogen peroxide (H2O2) concentrations ranging from 5.8 to 96 μmol L−1 in rainwater, which may contribute to the oxidation and removal of As. However, the influence of natural organic matter, such as humic acid (HA), on rainwater-borne H2O2-induced Fenton processes for the oxidation and removal of As remains unclear. In this study, the Fenton process was employed to investigate changes in As(V), As(III), and their mixtures, both in the presence and absence of HA. The results showed that low concentrations of HA (0–10 mg/L) promoted the oxidation of As(III) and removal of As(V) when As(V) and As(III) were present individually. However, when As(V) and As(III) coexisted, HA inhibited the Fenton process for As(V) removal. This inhibition was likely due to As(III) competing strongly with HA for hydroxyl radicals in the Fenton reaction system. Additionally, the presence of HA hindered the Fe(III)-driven removal of As(V), a product of the Fenton reaction. These findings further enhance our understanding of the potential role of rainwater-borne H2O2 in the transformation of As species in open water environments.

Novel Pyrroloquinoline Quinone-Modified Cerium Oxide Nanoparticles and Their Selective Cytotoxicity Under X-Ray Irradiation

Ionizing radiation leads to the development of oxidative stress and damage to biologically important macromolecules (DNA, mitochondria, etc.), which in turn lead to cell death. In the case of radiotherapy, both cancer cells and normal cells are damaged. In this regard, the development of new selective antioxidants is relevant. In this study, we first investigated the redox activity of cerium oxide-pyrroloquinoline quinone nanoparticles (CeO2@PQQ NPs) and their cytotoxic effects on normal (mouse fibroblasts, L929) and cancer (mouse adenocarcinoma, EMT6/P) cell cultures. Furthermore, the biological activity of CeO2@PQQ NPs was evaluated in comparison with that of CeO2 NPs and PQQ. The nanoparticles demonstrated pH-dependent reductions in the content of hydrogen peroxide after X-ray exposure. Our findings indicate that viability of EMT6/P cells was more adversely affected by CeO2@PQQ NPs at lower concentrations (0.1 μM) compared to L929. Following X-ray irradiation at a dose of 5 Gy, significant changes in mitochondrial potential (by 29%) and decreased glutathione levels (by 32%) were also observed in EMT6/P culture following irradiation and incubation with CeO2@PQQ NPs. Furthermore, EMT6/P exhibited a 2.5-fold increase in micronuclei and a 2-fold reduction in survival fraction compared to L929. It is hypothesized that CeO2@PQQ NPs may exhibit selective cytotoxicity and radiosensitizing properties against EMT6/P cancer cells. The findings suggest that CeO2@PQQ NPs may have potential as a selective redox-active antioxidant/pro-oxidant in response to X-ray radiation.