Spin Trap DMPO Research Articles

Near UV and Visible Light Photodegradation in Solid Formulations: Generation of Carbon Dioxide Radical Anions from Citrate Buffer and Fe(III).

Near UV and visible light photodegradation can target therapeutic proteins during manufacturing and storage. While the underlying photodegradation pathways are frequently not well-understood, one important aspect of consideration is the formulation, specifically the formulation buffer. Citrate is a common buffer for biopharmaceutical formulations, which can complex with transition metals, such as Fe(III). In an aqueous solution, the exposure of such complexes to light leads to the formation of the carbon dioxide radical anion (•CO2-), a powerful reductant. However, few studies have characterized such processes in solid formulations. Here, we show that solid citrate formulations containing Fe(III) lead to the photochemical formation of •CO2-, identified through DMPO spin trapping and HPLC-MS/MS analysis. Factors such as buffers, the availability of oxygen, excipients, and manufacturing processes of solid formulations were evaluated for their effect on the formation of •CO2- and other radicals such as •OH.

Triggering “signal-on” photoelectrochemical responses by heterojunction transition for selective detection of copper(II) based on Pd/MoS2@g-C3N4 nanocomposites

Controlling the concentration of copper(II) in aquatic systems is of importance for human health. Numerous traditional technologies to detect Cu2+ may encounter with limitations, such as high signal background and complicated operation. Herein, a highly selective photoelectrochemical (PEC) sensor is proposed for the “signal-on” detection of Cu2+ employing g-C3N4 nanosheets with MoS2 and Pd quantum dots deposited (Pd/MoS2@g-C3N4). Pd/MoS2@g-C3N4 could present the enhanced photocurrents of specific responses to Cu2+ under light irradiation. MoS2 quantum dots on the sensor are agglomerated into MoS2 bulk during sensing Cu2+, forming an efficient Z-scheme heterojunction. The heterojunction transition induced photoelectrons transferring from the bulk MoS2 to g-C3N4, resulting in “signal-on” PEC responses. Such Z-scheme heterojunction has conquered the traditional heterojunction towards “signal-on” mechanism, that was further verified by band structure measurements and DMPO spin trapping ESR analysis. Photocurrent intensities increased gradually with the addition of incremental Cu2+ concentrations, achieving a detection limit of 0.21 μM and a broad linear interval range from 1 μM to 1 mM with high selectivity and stability. This work may open a new door towards the in situ construction of g–C3N4–based Z-scheme heterojunctions for the signal-on PEC sensing platform, providing wide applications in environmental monitoring and food safety.

Thylakoid Rhodanese-like Protein-Ferredoxin:NADP+ Oxidoreductase Interaction Is Integrated into Plant Redox Homeostasis System.

In vascular plants, the final photosynthetic electron transfer from ferredoxin (Fd) to NADP+ is catalyzed by the flavoenzyme ferredoxin:NADP+ oxidoreductase (FNR). FNR is recruited to thylakoid membranes via an integral membrane protein TROL (thylakoid rhodanese-like protein) and the membrane associated protein Tic62. We have previously demonstrated that the absence of TROL triggers a very efficient superoxide (O2•-) removal mechanism. The dynamic TROL-FNR interaction has been shown to be an apparently overlooked mechanism that maintains linear electron flow before alternative pathway(s) is(are) activated. In this work, we aimed to further test our hypothesis that the FNR-TROL pair could be the source element that triggers various downstream networks of chloroplast ROS scavenging. Tandem affinity purification followed by the MS analysis confirmed the TROL-FNR interaction and revealed possible interaction of TROL with the thylakoid form of the enzyme ascorbate peroxidase (tAPX), which catalyzes the H2O2-dependent oxidation of ascorbate and is, therefore, the crucial component of the redox homeostasis system in plants. Further, EPR analyses using superoxide spin trap DMPO showed that, in comparison with the wild type, plants overexpressing TROL (TROL OX) propagate more O2•- when exposed to high light stress. This indicates an increased sensitivity to oxidative stress in conditions when there is an excess of membrane-bound FNR and less free FNR is found in the stroma. Finally, immunohistochemical analyses of glutathione in different Arabidopsis leaf cell compartments showed highly elevated glutathione levels in TROL OX, indicating an increased demand for this ROS scavenger in these plants, likely needed to prevent the damage of important cellular components caused by reactive oxygen species.

Electro-oxidation of tannery wastewater to achieve zero discharge – a step towards sustainability

ABSTRACT Pilot-scale electro-oxidation equipment with a functional capacity of 0.2 m3/hr, with titanium electrodes coated with TiO2/RuO2/IrO2 as both anodes and cathodes, was designed. It was installed on the premises of a commercial tannery. The waste streams from all the unit processes were combined. The composite wastewater, after conventional pre-treatment was subjected to electro-oxidation. The treated wastewater was reused four times with intermittent electro-oxidation treatment, after each reuse. EO could bring about a significant reduction in pollution load. Reduction in BOD, COD, TKN and TSS was 92%, 87.5%, 96.2% and 94.6% respectively. Generation of oOCl radicals, during electro-oxidation, were ascertained with DMPO-spin trapping techniques using Electron Spin Resonance (ESR) spectroscopy. The characteristics of the treated wastewater indicated that the wastewater was fit for reuse. No significant change in the quality of the water after each reuse was observed. The physical properties of the leathers obtained following the reuse processes were akin to those of the control leathers, which was indicative that the reuse did not cause adverse quality deviations. This technique could provide the plausibility for minizine the discharge of wastewater to near-zero level.

The effect of Luteolin on DNA damage mediated by a copper catalyzed Fenton reaction

Luteolin has been reviewed as a flavonoid possessing potential cardioprotective, anti-inflammatory, anti-cancer activities. Having multiple biological effects, luteolin may act as either an antioxidant or a pro-oxidant. In this work, the protective role of copper(II)-chelation by luteolin on DNA damage via the Cu-Fenton reaction was studied. EPR and UV–vis spectroscopic data demonstrated that the luteolin, lacking 3-OH group, chelates to Cu(II) via the 5-OH and 4-CO groups, respectively. EPR spin trapping experiments using DMPO spin trap confirmed that the coordination of luteolin to Cu(II) significantly suppressed formation of hydroxyl and superoxide radicals (by 80%) in a Cu-Fenton system. Absorption titrations showed that the chelation of Cu(II) by luteolin slightly increased the mild intercalation strength of its interaction with DNA, as compared with free luteolin. Comparison with kaempferol and quercetin revealed, that the strength of the interaction between the free flavonoids/Cu-flavonoid complexes with DNA is only mildly affected by the presence/absence of 3-OH group. Due to the differences in the sensitivities of absorption titrations and viscometry, the latter confirmed weaker DNA intercalating efficiency of Cu-luteolin complex than does free luteolin. A dose dependent protective effect of luteolin against ROS-induced DNA damage was observed using gel electrophoresis. This effect was more pronounced compared to quercetin and kaempferol. In conclusion, the administration of luteolin to patients suffering from oxidative stress-related diseases with disturbed Cu-metabolism such as Alzheimer's diseases (antioxidant effect) and certain cancers (prooxidant effect) may have several health benefits.

EPR Spin-Trapping Study of Free Radical Intermediates in Polyalphaolefin Base Oil Autoxidation

Autoxidation is a set of spontaneous oxygen-mediated radical reactions common to degradation processes of all hydrocarbon-based materials. In this work, EPR (electron paramagnetic resonance) spin-trapping technique was used to study radical species involved in the autoxidation of a sample of synthetic base oil. A sample of polyalphaolefin base oil was aged at 140°C in the presence of oxygen and the difference in the tendency to generate radical species between the aged and non-aged samples of the same base oil was investigated using DMPO (5,5-dimethyl-1-pyrroline N-oxide) spin-trap. The ageing was performed in such a way that a small amount of hydroperoxides, the primary and key intermediate in autoxidation reactions, accumulated in the sample. Subsequently, the degradation of hydroperoxides was triggered by three different means: thermal treatment, introduction of soluble transition metal ions, and UV irradiation. Radical intermediates were monitored by EPR spin trapping; mixtures of peroxyl, alkoxyl, and carbon-centered radicals were detected and their origin was discussed.

The Nitrone Spin Trap DMPO Prevents Lipopolysaccharide-induced Pro-inflammatory Programming of Macrophages

The Nitrone Spin Trap DMPO Prevents Lipopolysaccharide-induced Pro-inflammatory Programming of Macrophages

Nanomaterial categorization by surface reactivity: A case study comparing 35 materials with four different test methods

Nanomaterials (NMs) can be manufactured in plenty of variants differing in their physicochemical properties. Functional assays can be highly useful to cope with the enormous variability by supporting prioritization and categorization. Oxidative potential (OP) seems to be in particular important in this context and different assays are available. However, their reliability and predictivity are not well-characterized.This study compares four different test methods for measuring NM OP. Reactive oxygen species (ROS) generation was measured on a set of 35 different materials, all extensively characterized with respect to physicochemical properties and most of them with respect to toxicity. Different acellular assays were applied, namely electron spin resonance (ESR) spectroscopy using CPH spin probe and DMPO spin trap, and the ferric reduction ability of serum (FRAS) assay. In addition, protein carbonylation as a marker for oxidative protein damage was analyzed in NRK-52E cells. All assays were assessed individually for their predictivity compared to established toxicological endpoints. We also aimed to identify the optimal assay combination using multivariate logistic regression and other statistical measures.BET surface area-based doses were more suitable to relate surface reactivity to toxicity. In addition, normalization to the deposited dose was advantageous for cellular assays as it improved the predictivity for in vitro as well as in vivo toxicity. The carbonylation assay, potentially in combination with ESR (DMPO spin trap) or FRAS assay, led to the best predictive performance.In summary, we propose a testing strategy for NM OP and demonstrated the applicability in an extended case study on 35 materials. This work is an important contribution towards reliable grouping and testing strategies for NMs.

Superoxide and Hydroperoxyl Radical Spin Trapping Using 5,5- Dimethyl-1-Pyrroline N-Oxide in Dehydrated N,N-Dimethylformamide

Herein, superoxide radical (O2•−) spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in dehydrated N,N-dimethylformamide (DMF) solution is investigated via electrochemistry and electron spin resonance (ESR) measurements supported by theoretical calculations. In aprotic environments, DMPO gradually reacts with electrogenerated O2•−; however, the trapping kinetics are considerably slow and cannot enable successful radical trapping in aqueous biological experiments. Alternatively, adding a proton source changes the voltammetric behavior, rendering the detection of the spin adduct easy with ESR. These results suggest that the proton addition to O2•−, which forms a hydroperoxyl radical (HO2•), accelerates the kinetics of radical trapping. Accordingly, we propose that the actual target of DMPO spin trapping is HO2• rather than O2•−.

Enhanced Fenton-like catalytic performance of Cu-Al/KIT-6 and the key role of O2 in triggering reaction

Framework Cu doped Al2O3 dispersed on KIT-6 (Cu-Al/KIT-6) was synthesized by the ultrasonic impregnation method and characterized by multi-technologies. The catalyst performed superior catalytic performance and stability for bisphenol A (BPA) degradation in heterogeneous Fenton-like catalysis. Especially, the effect of O2 and N2 on BPA degradation was detected over Cu-Al/KIT-6 in the presence of hydrogen peroxide (H2O2). DMPO spin-trap electron spin resonance (ESR) experiments indicated that O2 can be activated to produce reactive oxygen species (ROS) by Cu(I) on the surface of Cu-Al/KIT-6. Meanwhile, O2 as an electron acceptor can trigger the reaction at the beginning of reaction, which decreased the consumption of H2O2. In addition, BPA and its intermediate products chelate with Cu(II) to form Cu(II)-phenol complex, resulting in a series of reactions to further promote BPA degradation. These findings provide useful insights into the fundamental theories of Fenton catalysts via interface engineering for practical application.

Photogeneration of reactive oxygen species over ultrafine TiO2 particles functionalized with rutin\u2013ligand induced sensitization and crystallization effects

Interaction of amorphous and crystalline TiO2 ultrafine particles (2–6 nm) with rutin results in the formation of colored nanomaterials of an excellent dispersity and enhanced colloidal stability in aqueous media. The FTIR and Raman spectra confirmed attachment of the rutin ligand via vicinal hydroxyl groups in a catechol-like fashion. The binding of rutin to amorphous TiO2 gives rise to spontaneous crystallization of the parent nanoparticles into hydrogen titanates (H2Ti3O7 and H2Ti12O25). Such structural transformations result in photosensitization toward visible light with enhanced efficiency of the charge separation and interfacial charge transfer processes, confirmed by detailed photoelectrochemical studies of the examined nanomaterials. The effectiveness of the photocatalytic ROS generation reactions was also strongly influenced by hydrogen peroxide, which plays a double role of a reactant prone to reduction and generation of hydroxyl radicals or a redox agent destroying the intra-band gap electronic states, suppressing thereby charge recombination. The photoinduced charge transfer processes lead to generation of various reactive oxygen species, which were detected by EPR using DMPO spin trap (HOO· detection) and in the reaction with terephthalic acid acting as a chemical scavenger (HO· detection). Complexation of TiO2 particles with rutin shifts the photogeneration of hydroperoxyl (HOO·) and hydroxyl (HO·) radicals toward visible light (λ > 400 nm). A triple effect of rutin attachment to titania was established. It consists in pronounced photosensitization, promotion of crystallization and enhancement of the colloidal stability of ultrafine titania particles. Environmental implications of these assets on the photoinduced redox reactions with hydrogen peroxide in aqueous solutions upon UV or visible light irradiation were also discussed.

Microcystin exposure worsens nonalcoholic fatty liver disease associated ectopic glomerular toxicity via NOX-2-MIR21 axis

NAFLD often results in cardiovascular, intestinal and renal complications. Previous reports from our laboratory highlighted NAFLD induced ectopic inflammatory manifestations in the kidney that gave rise to glomerular inflammation. Extending our studies, we hypothesized that existing inflammatory conditions in NAFLD could make the kidneys more susceptible to environmental toxicity. Our results showed that exposure of Microcystin-LR (MC) in NAFLD mice caused a marked increase in cellular scarring with a concomitant increase in mesangial cell activation as observed by increased α-SMA in the extracellular matrix surrounding the glomeruli. Renal tissue surrounding the glomeruli also showed increased NOX2 activation as shown by greater co-localization of p47 Phox and its membrane component gp91Phox both in the mesangial cell and surrounding tissue. Mechanistically, mesangial cells incubated with apocynin, nitrone spin trap DMPO and miR21 inhibitor showed significantly decreased α-SMA, miR21 levels and proinflammatory cytokine release in the supernatant. In parallel, mice lacking miR21, known to be activated by NOX2, when exposed to MC in NAFLD showed decreased mesangial cell activation. Strikingly, phenyl boronic acid incubated cells that were exposed to MC showed significantly decreased mesangial cell activation showing that peroxynitrite might be the major reactive species involved in mediation of the activation process, release of proinflammatory micro RNAs and cytokines that are crucial for renal toxicity. Thus, in conclusion, MC exposure causes NOX2 activation that leads to mesangial cell activation and toxicity via release of peroxynitrite that also represses PTEN by the upregulation of miR21 thus amplifying the toxicity.

ATP Mimics pH-Dependent Dual Peroxidase-Catalase Activities Driving H 2 O 2 Decomposition

Adenosine triphosphate (ATP) is produced mainly in the mitochondrion, and its primary task is to function as a ubiquitous energy currency to meet the cellular metabolic demands in biological system...

Detection of Free Oxygen Reduction Reaction Intermediates Generated at Pt Nanoparticles By Electron Paramagnetic Resonance Spectroscopy

In the search for clean energy conversion systems, PEM fuel cells have attracted a lot of attention over the last decades. Nanostructured electrocatalysts such as porous platinum nanoparticles (NPs) are considered one of the most promising advances to lower the cost of these fuel cells and make them more commercially attractive. The efficiency of these catalysts is limited by their activity towards the oxygen reduction reaction (ORR), and most research is thus focused on understanding reaction mechanisms and improving the activity. The mechanism is well understood for alkaline conditions, but there is still some debate for that under acidic conditions. It has been shown indirectly[1],[2] that radical intermediates formed during the reaction can desorb from the catalyst surface, but direct proof is still absent. More importantly, these free radicals are suspected to be responsible for the degradation of the carbon support, leading to the deactivation of the electrocatalyst NPs[3]. We propose an approach to detect and identify the free radicals produced during the ORR using electron paramagnetic resonance (EPR) spectroscopy. EPR spectroscopy combined with spin trapping has been shown to be useful for detecting radicals produced in electrochemical reactions[4],[5]. This method relies on binding the free oxygen radicals to the spin trap DMPO, forming the stable radical complex DMPO-OH•. The DMPO-OH complex can be detected using an EPR spectrometer. Custom-made glassy carbon RDE’s with a large geometrical surface area have been designed and were loaded with Pt nanoparticles via double pulse electrodeposition. The large surface area is necessary in order to produce sufficiently large amounts of free radicals to be detectable in the EPR spectrometer. A DMPO-OH• signal is formed and increases in strength for the duration of the ORR experiments. Furthermore, we observe a direct correlation between the charge produced during the experiment and the strength of the DMPO-OH• signal. This approach, capable of detecting the free oxygen radicals produced during the ORR, is employed to shed light on the ORR mechanism at carbon electrodes loaded with Pt NPs in acidic conditions.

An urchin-like Ag3PO4/Pd/LaPO4 photocatalyst with Z-scheme heterojunction for enhanced hydrogen evolution

An urchin-like LaPO4-based nanocomposite integrating Ag3PO4 and Pd has been initially synthesized via a controllable self-assembly route, with enhanced photocatalysis and ultrastable structure for the synergistic hydrogen (H2) evolution under sunlight. Citric acid was employed as a structure-mediated agent to guide the oriented growth of LaPO4 along [101] facet at room temperature, showing the urchin-like 3D structure. Furthermore, Pd and Ag3PO4 were coated in turn resulting in the Ag3PO4/Pd/LaPO4 nanocomposite, in which Pd and Ag3PO4 could act as the functions of electron receptor and electron donor in the photocatalysis, respectively. It was discovered that the as-developed nanocomposite could present the robust photocatalysis and stable morphology after consecutive uses. Based on the band structure analysis, a Z-scheme system of Ag3PO4/Pd/LaPO4 was thereby proposed for the sunlight photocatalysis, as testified by DMPO spin trapping ESR spectra. Also, the photoluminescence and electrochemical impedance of nanocomposites were conducted, indicating that the improved carriers properties should be responsible mainly for the dramatically enhanced photocatalytic activities. Moreover, the outstanding photocatalytic performances of Ag3PO4/Pd/LaPO4 were demonstrated in H2 evolution (1084.3 μmol·g−1·h−1) under sunlight. Importantly, such a citric acid-controlled self-assembly route may pave the way toward the fabrication of multi-component photocatalyst tailored for the wide photocatalytic applications.

Using MRI to measure in vivo free radical production and perfusion dynamics in a mouse model of elevated oxidative stress and neurogenic atrophy

Mitochondrial dysfunction, reactive oxygen species (ROS) and oxidative damage have been implicated to play a causative role in age-related skeletal muscle atrophy and weakness (i.e. sarcopenia). Mice lacking the superoxide scavenger CuZnSOD (Sod1−/−) exhibit high levels of oxygen-derived radicals and oxidative damage, associated with neuronal and muscular phenotypes consistent with sarcopenia. We used magnetic resonance imaging (MRI) technology combined with immunospin-trapping (IST) to measure in vivo free radical levels in skeletal muscle from wildtype, Sod1−/− and SynTgSod1−/− mice, a mouse model generated using targeted expression of the human Sod1 transgene specifically in neuronal tissues to determine the impact of motor neuron degeneration in muscle atrophy. By combining the spin trap DMPO (5,5-dimethyl-1-pyrroline N-oxide) and molecular MRI (mMRI), we monitored the level of free radicals in mouse hindlimb muscle. The level of membrane-bound macromolecular radicals in the quadriceps muscle was elevated by ~3-fold in Sod1−/− mice, but normalized to wildtype levels in SynTgSod1−/− rescue mice. Skeletal muscle mass was reduced by ~25–30% in Sod1−/− mice, but fully reversed in muscle from SynTgSod1−/− mice. Using perfusion MRI we also measured the dynamics of blood flow within mouse hindlimb. Relative muscle blood flow in Sod1−/− is decreased to ~50% of wildtype and remained low in the SynTgSod1−/− mice. Our findings are significant in that we have shown for the first time that in vivo free radical production in skeletal muscle is directly correlated to muscle atrophy in an experimental model of oxidative stress. Neuron-specific expression of CuZnSOD reverses the in vivo free radical production in skeletal muscle in the Sod1−/− mouse model and prevents muscle atrophy. These results further support the feasibility of using in vivo assessments of redox status in the progression of a pathological process such as sarcopenia. This approach can also be valuable for evaluating responses to pharmacologic interventions.

Exposure to Electronic Cigarette Vapor Causes Systemic Accumulation of Biomolecular Free Radicals

Little is known regarding the impact of electronic cigarette (e‐cig) usage in the human body. However, emerging literature suggests that vaping results in endothelial cell mediated vascular impairments, altered thrombosis, and depressed immune function (similar to that observed with smoking). Since e‐cigs are marketed as a ‘safer’ alternative to traditional cigarettes, it is important to characterize mechanisms through which e‐cigs may induce cellular insult. It is known that traditional cigarette use results in systemic accumulation of biomolecular free radicals (BFR), thus we sought to determine whether exposure to e‐cig vapor will result in significant systemic increases in BFR. We hypothesize that vaping will increase the relative amount of BFR accumulation in vital tissues in a time‐dependent manner.To identify BFR in‐vivo, C57BL/7 mice were given IP 1.5 g/kg DMPO (5,5‐dimethyl‐l‐pyrroline‐l‐oxide) spin‐trap in 2 doses over 1 hour, and acutely exposed to french vanilla‐flavored e‐cig vapor (18 mg nicotine) for either 1 hour (n=3) or 4 hours (n=3). Sham mice were exposed to ambient air (n=3). Immediately following exposure, the mice were anesthetized, perfused with PBS via intra‐ventricular catheterization, organs/tissues were harvested and fixed in paraformaldehyde/sucrose, flash‐frozen in liquid nitrogen and then fixed in TFM. Imaging from fluorescent immunohistochemical labeling revealed significant increase BFR accumulation in the liver (223%, p<0.05) and to lesser extent in the heart (133%, p<0.05) in 1‐hour exposed animals. Similar trends for increased BFR (albeit not statistically significant) were found in the lung (236%) and brain (124%) in 4‐hour exposed group compared to air exposed controls.In summary, we found significant increase in the presence of BFR in the liver and heart of mice acutely exposed to 1‐hour of e‐cig vapor compared to controls, with similar trends in other tissue beds (lung, brain) after 4‐hours vape exposure. This is a pilot study which needs additional samples for further evaluation, but suggests that vaping induces BFR accumulation in multiple organs which could lead to cellular damage and tissue dysfunction.Support or Funding InformationSupport: WVU Cancer Institute Philip R Dino Innovative Research Grant (IMO); Transition Grant Support; Office of Research and Graduate Education (IMO), WVU Health Sciences Center APS STRIDE Fellowship (JO); NIHGMS 5U54GM104942‐03 (PDC)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effective photocatalytic salicylic acid removal under visible light irradiation using Ag2S/AgI-Bi2S3/BiOI with Z-scheme heterojunctions

A photocatalyst of Ag2S/AgI-Bi2S3/BiOI was synthesized with Z-scheme heterojunctions simply by the S2−-I− anion exchange route showing broad visible light response and enhanced photogenerated carriers properties. The yielded Ag2S/AgI-Bi2S3/BiOI could feature the reactive active sites of Bi2S3/BiOI and Ag2S/AgI heterojunctions, serving as the photogenerated electron donors and photogenerated electron acceptors, respectively. Ag bridges were generated to ensure the construction of Z-scheme strategy, which further improved the migration direction of charge carriers in nanocomposites. Moreover, the analysis of photoluminescence spectra and electrochemical impedance spectroscopy could testified the functions of heterojunctions, which dramatically achieved the enhanced separation and transferring capacity of photogenerated electron-hole pairs in photocatalyst, respectively. In addition, Ag2S/AgI-Bi2S3/BiOI with large specific surface area facilitated the efficient photocatalytic removal of salicylic acid (SA) (up to 89.2%) under visible light. Favorable photocatalytic production of hydrogen peroxide (H2O2) were obtained in pure water driven by the visible light. Besides, by the results of capture experiments, DMPO spin trapping ESR spectra and band structures analysis, the Z-scheme manner of the nanocomposites could promote the reduction ability of photo-generated electrons so as to produce numerous ·O2− during the photocatalytic reactions toward the photocatalytic SA removal and H2O2 production.

Quantification and characterization of radical production in human, animal and 3D skin models during sun irradiation measured by EPR spectroscopy

Sun radiation is indispensable to our health, however, a long term and high exposure could lead to erythema, premature skin aging and promotion of skin tumors. An underlying pathomechanism is the formation of free radicals. First, reactive oxygen species (*OH, *O2-) and then, secondary lipid oxygen species (C centered radicals, CCR) are formed. A high amount of free radicals results in oxidative stress with subsequent cell damage. In dermatological research different skin models are used, however, comparative data about the cutaneous radical formation are missing. In this study, the radical formation in porcine-, (SKH-1) murine-, human- ex vivo skin and reconstructed human skin (RHS) were investigated during simulated sun irradiation (305–2200 nm), with X-band EPR spectroscopy. The amount of radical formation was investigated with the spin probe PCA exposed to a moderate sun dose below one minimal erythema dose (MED, ~25 mJ/cm2 UVB) in all skin models. Furthermore, the *OH and *CCR radical concentrations were measured with the spin trap DMPO within 0–4 MED (porcine-, human skin and RHS).The highest amount of radicals was found in RHS followed by murine and porcine, and the lowest amount in human ex vivo skin. In all skin models, more *OH than CCR radicals were found at 0–4 MED. Additionally, this work addresses the limitations in the characterization with the spin trap DMPO.The measurements have shown that the most comparable skin model to in vivo human skin could differ depending on the focus of the investigation. If the amount of radial production is regarded, RHS seems to be in a similar range like in vivo human skin. If the investigation is focused on the radical type, porcine skin is most comparable to ex vivo human skin, at an irradiation dose not exceeding 1 MED. Here, no comparison to in vivo human skin is possible.

A porous activated carbon supported Pt catalyst for the oxidative degradation of poly[(naphthaleneformaldehyde)sulfonate

Abstract Wet catalytic oxidation of sodium poly[(naphthaleneformaldehyde)sulfonate], a hazardous contaminant of wastewater streams from the textiles industry, by hydrogen peroxide under ambient conditions was explored over platinum supported on a porous activated carbon (PAC). Bulk and surface properties of the Pt/PAC catalyst were investigated by XRD, XPS, SEM, TEM, FTIR, EPR and thermogravimetric analysis. The parent PAC, derived from pyrolysis and subsequent activation of rice husks, exhibited significant micro- and mesoporosity, and a high degree of surface oxidation. Incorporation of 1.7 wt% Pt resulted in mesopore blockage, and a corresponding drop in surface area, associated with the formation of large ∼8 nm metallic nanoparticles. Poly[(naphthaleneformaldehyde)sulfonate] oxidative degradation was studied as a function of reactant concentration and solution pH, revealing first order decomposition kinetics and good activity over pH 3–9 at ambient temperature. Electron Paramagnetic Resonance (EPR)-DMPO spin trapping experiments confirm that oxidation of the organic pollutant proceeded via hydroxyl radical generation. The 1.7 wt% Pt/PAC catalyst showed excellent catalyst stability for five consecutive runs over 25 h in a fluidised bed reactor, delivering > 85% removal of 100 mg/L sulfonate with negligible Pt leaching or activity loss, and comparable performance for treatment of a real tannery effluent stream with a COD equivalent of 1860 mg/L.