H2O2 diffusion
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Natural antioxidants, like phenolic acids, possess a unique chemical space that can protect cellular components from oxidative stress. However, their polar carboxylic acid chemotype reduces full intracellular antioxidant potential due to limited diffusion through biological membranes. Here, we have designed and developed a new generation of hydrophobic turn-on fluorescent antioxidant precursors that upon penetration of the cell membrane, reveal a more polar and more potent antioxidant core and simultaneously become fluorescent allowing their intracellular tracking. Their activation is stimulated by polarity alteration by sensing intracellular signals and specifically biothiols. In our design, the carboxylic group of phenolic acids that originally restricts cell entrance is derivatized and conjugated through Copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) to a coumarin derivative that its fluorescence properties are quenched with a biothiol activatable element. This more hydrophobic precursor readily penetrates cell membrane and once inside the cell the antioxidant core is revealed upon sensing glutathione, its fluorescence is restored in a turn-on manner and the generation of a more polar character traps the molecule inside the cell. This turn-on fluorescent antioxidant precursor that can be applied to phenolic acids, was developed for rosmarinic acid and the conjugate was named as RCG. The selectivity and responsiveness of RCG towards the most abundant biothiols was monitored through a variety of biophysical techniques including UV-Vis, fluorescence and NMR spectroscopy. The electrochemical behavior and free radical scavenging capacity of the precursor RCG and the active compound (RC) was evaluated and compared with the parent compound (rosmarinic acid) through cyclic voltammetry and EPR spectroscopy, respectively. The stability of the newly synthesized bioactive conjugate RC was found significantly higher than the parent rosmarinic acid when exposed to oxygen. Cell uptake experiments were conducted and revealed the internalization of RCG. The degree of intracellular DNA protection offered by RCG and its active drug (RC) on exposure to H2O2 was also evaluated in Jurkat cells.
Objective. Electric stimulation delivered by implantable electrodes is a key component of neural engineering. While factors affecting long-term stability, safety, and biocompatibility are a topic of continuous investigation, a widely-accepted principle is that charge injection should be reversible, with no net electrochemical products forming. We want to evaluate oxygen reduction reactions (ORR) occurring at different electrode materials when using established materials and stimulation protocols.Approach. As stimulation electrodes, we have tested platinum, gold, tungsten, nichrome, iridium oxide, titanium, titanium nitride, and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). We use cyclic voltammetry and voltage-step amperometry in oxygenated versus inert conditions to establish at which potentials ORR occurs, and the magnitudes of diffusion-limited ORR currents. We also benchmark the areal capacitance of each electrode material. We use amperometric probes (Clark-type electrodes) to quantify the O2and H2O2concentrations in the vicinity of the electrode surface. O2and H2O2concentrations are measured while applying DC current, or various biphasic charge-balanced pulses of amplitude in the range 10-30μC cm-2/phase. To corroborate experimental measurements, we employ finite element modelling to recreate 3D gradients of O2and H2O2.Main results. All electrode materials support ORR and can create hypoxic conditions near the electrode surface. We find that electrode materials differ significantly in their onset potentials for ORR, and in the extent to which they produce H2O2as a by-product. A key result is that typical charge-balanced biphasic pulse protocols do lead to irreversible ORR. Some electrodes induce severely hypoxic conditions, others additionally produce an accumulation of hydrogen peroxide into the mM range.Significance. Our findings highlight faradaic ORR as a critical consideration for neural interface devices and show that the established biphasic/charge-balanced approach does not prevent irreversible changes in O2concentrations. Hypoxia and H2O2can result in different (electro)physiological consequences.
Heterogeneous iron species at the mineral/water interface are important catalysts for the generation of reactive oxygen species at circumneutral pH. One significant pathway leading to the formation of such species arises from deposition of dissolved iron onto mineral colloids due to changes in redox conditions. This study investigates the catalytic properties of Fe impregnated on silica, alumina, and titania nanoparticles (as prototypical mineral colloids). Fe impregnation was carried out by immersing the mineral nanoparticles in dilute Fe(II) or Fe(III) solutions at pH 6 and 3, respectively, in an aerobic environment. The uptake of iron per unit surface area follows the order of nTiO2 > nAl2O3 > nSiO2 for both types of Fe precursors. Impregnation of mineral particles in Fe(II) solutions results in predominantly Fe(III) species due to efficient surface-mediated oxidation. The catalytic activity of the impregnated solids to produce hydroxyl radical (·OH) from H2O2 decomposition was evaluated using benzoic acid as a probe compound under dark conditions. Invariably, the rates of benzoic acid oxidation with different Fe-laden particles increase with the surface density of Fe until a critical density above which the catalytic activity approaches a plateau, suggesting active Fe species are formed predominantly at low surface loadings. The critical surface density of Fe varies with the mineral substrate as well as the aqueous Fe precursor. Fe impregnated on TiO2 exhibits markedly higher activity than its Al2O3 and SiO2 counterparts. The speciation of interfacial Fe is analyzed with diffuse reflectance UV-vis analysis and interpretation of the data in the context of benzoic oxidation rates suggests that the surface activity of the solids for ·OH generation correlates strongly with the isolated (i.e., mononuclear) Fe species. Therefore, iron dispersed on mineral colloids is a significant form of reactive iron surfaces in the aquatic environment.
- MeSH
- hydroxylový radikál chemie MeSH
- katalýza MeSH
- koloidy chemie MeSH
- minerály chemie MeSH
- nanočástice MeSH
- oxid hlinitý chemie MeSH
- oxid křemičitý chemie MeSH
- oxidace-redukce MeSH
- peroxid vodíku chemie MeSH
- roztoky chemie MeSH
- titan chemie MeSH
- voda chemie MeSH
- železité sloučeniny chemie MeSH
- železo chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Electrospun polymeric nanofiber materials doped with 5,10,15,20-tetraphenylporphyrin (TPP) photosensitizer were prepared from four different polymers and were characterized with microscopic methods, steady-state, and time-resolved fluorescence and absorption spectroscopy. The polymers used included polyurethane Larithane™ (PUR), polystyrene (PS), polycaprolactone (PCL), and polyamide 6 (PA6). The antibacterial activity of all nanofiber materials against E. coli was activated by visible light and it was dependent on oxygen permeability/diffusion coefficients and the diameter of the polymeric nanofibers. This activity is based on oxidation ability of singlet oxygen O₂(¹Δ(g)) that is generated upon irradiation. All tested nanofiber materials exhibited prolonged antibacterial properties, even in the dark after long-duration irradiation. The post-irradiation effect was explained by the photogeneration of H₂O₂, which provided the material with long-lasting antibacterial properties.
- MeSH
- antibakteriální látky chemie farmakologie MeSH
- Escherichia coli účinky léků MeSH
- fotosenzibilizující látky chemie MeSH
- kaprolaktam analogy a deriváty chemie MeSH
- nanovlákna chemie MeSH
- oxidancia chemie MeSH
- peroxid vodíku chemie MeSH
- polyestery chemie MeSH
- polymery chemie MeSH
- polystyreny chemie MeSH
- polyurethany chemie MeSH
- porfyriny chemie MeSH
- singletový kyslík chemie MeSH
- světlo MeSH
- testování materiálů MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
Koncentrovaný peroxid vodíku je žíravý a expozice může mít za následek lokální poškození tkáně. Prezentujeme kazuistiku pětiletého chlapce, který po napití se z 30% roztoku peroxidu vodíku začal zvracet a stěžovat si na bolest břicha v epigastriu. Radiologické vyšetření prokázalo vzduchovou embolizaci do portálního řečiště. Při doplňující gastrointestinální endoskopii byla potvrzena difuzní hemoragická gastritida. Byl sledován na lůžku 12 dnů a následně propuštěn do ambulantní péče. Kontrolní endoskopické vyšetření devět dnů od poleptání konstatovalo nález erytematózní gastritidy.
Concentrated hydrogen peroxide is caustic and exposure may result in local tissue damage. We report the case of a 5-year-oldboy who ingested one mouthful of 30% hydrogen peroxide and presented with vomiting and epigastric pain. The radiograhicevaluation found portal venous gas embolism. In addition, upper gastrointestinal endoscopy performed revealed diffuse hemorrhagicgastritis. He was observed for 12 days and discharged. Follow-up endoscopy nine days later, showed erythematous gastritis.
- Klíčová slova
- kyslíková embolie, hemoragická gastritida,
- MeSH
- chemické popálení diagnóza etiologie MeSH
- gastritida diagnóza etiologie farmakoterapie MeSH
- gastrointestinální krvácení diagnóza chemicky indukované MeSH
- kyslík MeSH
- lidé MeSH
- nemoci duodena diagnóza chemicky indukované MeSH
- nemoci jícnu diagnóza chemicky indukované MeSH
- peroxid vodíku * otrava MeSH
- portální systém * patologie MeSH
- předškolní dítě MeSH
- vzduchová embolie * diagnóza etiologie terapie MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- předškolní dítě MeSH
- Publikační typ
- kazuistiky MeSH
- práce podpořená grantem MeSH
This article describes and particularly explains a new phenomenon of persistent microbicidal effect of water previously exposed to the low-temperature plasma, which cannot be attributed to the acidification only. The direct microbicidal action of plasma is well documented, being mediated by number of reactive particles with a short lifetime. However, we observed the microbicidal effect also in exposed water stored for a month, where it must be mediated by stable particles. In water and in phosphate-buffered saline, the formation of NO(x) and corresponding acids, H(2)O(2) and O(3) was confirmed after exposition to the low-temperature plasma generated in air by DC negative glow corona and positive streamer discharge. The time course of acidification, H(2)O(2) and O(3) formation were deremined. Except uncertain traces of HCN, SIFT-MS analysis of exposed liquids reveals no additional reactive compounds. The microbicidal effect persists almost unchanged during 4 weeks of storage, although O(3) completely and H(2)O(2) almost disappears. Staphylococcus epidermidis and Escherichia coli were inactivated within 10 min of incubation in exposed liquids, Candida albicans needs at least 1 h. The solutions prepared by artificial mixing of reactive compounds mimic the action of exposed water, but in lesser extent. The acid milieu is the main cause of the microbicidal effect, but the possibility of still unidentified additional compound remains open.
- MeSH
- antiinfekční látky chemie farmakologie MeSH
- Candida albicans účinky léků MeSH
- elektrická vodivost MeSH
- Escherichia coli účinky léků MeSH
- hmotnostní spektrometrie MeSH
- koncentrace vodíkových iontů MeSH
- ozon chemie MeSH
- peroxid vodíku chemie MeSH
- plazmové plyny chemie MeSH
- Staphylococcus epidermidis účinky léků MeSH
- voda chemie farmakologie MeSH
- vzduch MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- DNA-fotolyasa genetika metabolismus MeSH
- Escherichia coli genetika metabolismus MeSH
- finanční podpora výzkumu jako téma MeSH
- peroxid vodíku farmakologie MeSH
- Saccharomyces cerevisiae enzymologie účinky záření MeSH
- viabilita buněk účinky léků účinky záření MeSH
Twelve lactobacilli isolates from mucosa of 3-5-week-old weaned pigs were found to exert good antimicrobial activity against common porcine pathogens (S. aureus, B. cereus, E. coli, C. perfringens). Two of them produced in addition to lactic acid also considerable amounts of acetic acid, and 6 of them produced hydrogen peroxide and metabolites other than organic acids. Isolates 4/26 and 2/25 (identified as L. crispatus or L. amylovorus) were inhibitory against most strains of S. aureus, B. cereus and E. coli, and especially the strain 4/26 survived well in simulated gastric and intestinal juice. Diarrhea-causing E. coli O8K88H9 Ent(+) was successfully inhibited by the growing culture as well as by the catalase-treated and neutralized supernatant of L. reuteri 12/26. Mucin degradation and multiple resistance to antibiotics were not observed.
- MeSH
- antibiotická rezistence MeSH
- Bacillus cereus účinky léků MeSH
- Clostridium perfringens účinky léků MeSH
- Escherichia coli účinky léků MeSH
- feces mikrobiologie MeSH
- ileum mikrobiologie MeSH
- kultivační média speciální farmakologie MeSH
- kultivační média farmakologie chemie MeSH
- kyselina mléčná farmakologie MeSH
- Lactobacillus izolace a purifikace metabolismus účinky léků MeSH
- muciny metabolismus MeSH
- nemoci prasat prevence a kontrola MeSH
- odstavení MeSH
- peroxid vodíku metabolismus MeSH
- přirozená imunita MeSH
- probiotika MeSH
- Staphylococcus aureus účinky léků MeSH
- střevní sliznice mikrobiologie MeSH
- Sus scrofa mikrobiologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
Osmotically inducible protein (OsmC) and organic hydroperoxide resistance protein (Ohr) are small, thiol-dependent peroxidases that comprise a family of prokaryotic protective proteins central to the defense against deleterious effects of organic hydroperoxides, which are reactive molecules that are formed during interactions between the host immune system and pathogens. Trichomonas vaginalis, a sexually transmitted parasite of humans, possesses OsmC homologues in its hydrogenosomes, anaerobic mitochondrial organelles that harbor enzymes and pathways that are sensitive to oxidative damage. The glycine decarboxylase complex (GDC), which consists of four proteins (i.e., L, H, P and T), is in eukaryotes exclusively mitochondrial enzymatic system that catalyzes oxidative decarboxylation and deamination of glycine. However, trichomonad hydrogenosomes contain only the L and H proteins, whose physiological functions are unknown. Here, we found that the hydrogenosomal L and H proteins constitute a lipoate-dependent redox system that delivers electrons from reduced nicotinamide adenine dinucleotide (NADH) to OsmC for the reductive detoxification of peroxides. Our searches of genome databases revealed that, in addition to prokaryotes, homologues of OsmC/Ohr family proteins with predicted mitochondrial localization are present in various eukaryotic lineages. Therefore, we propose that the novel OsmC-GDC-based redox system may not be limited to T. vaginalis.
- MeSH
- axenická kultura MeSH
- Escherichia coli genetika metabolismus MeSH
- exprese genu MeSH
- fylogeneze MeSH
- I. fáze biotransformace genetika MeSH
- kinetika MeSH
- klonování DNA MeSH
- mitochondrie metabolismus ultrastruktura MeSH
- oxidace-redukce MeSH
- peroxid vodíku metabolismus MeSH
- peroxidasy genetika metabolismus MeSH
- protozoální proteiny genetika metabolismus MeSH
- rekombinantní proteiny genetika metabolismus MeSH
- sekvence aminokyselin MeSH
- sekvenční homologie aminokyselin MeSH
- sekvenční seřazení MeSH
- systém štěpení glycinu genetika metabolismus MeSH
- Trichomonas vaginalis genetika metabolismus ultrastruktura MeSH
- vazba proteinů MeSH
- Publikační typ
- časopisecké články MeSH
