Spin Trapping Technique Research Articles

Radical Scavenging Capacity and In Vitro Cytoprotective Effects of Great Salt Lake-Derived Processed Mineral Water.

The Great Salt Lake, located in Utah, USA, is a saltwater lake with no outlet and is surrounded by vast mountains and salt deserts. We aimed to use Great Salt Lake-derived processed mineral water (hereafter termed as GSL-MW) for maintaining oral health. Therefore, we examined its radical scavenging activity as an antioxidant and its cytoprotective effect on human gingival fibroblasts (hGFs). The scavenging activity against O2•- radicals was determined by an electron spin resonance (ESR)-spin trapping technique using two kinds of O2•- generation systems; however, we could not reach any concrete conclusion because of the interference caused by GSL-MW in both systems. Detection of ·OH radicals using the ESR-spin trapping technique and kinetic analyses using double-reciprocal plots (corresponding to Lineweaver-Burk plots that are used to represent enzyme kinetics) revealed that GSL-MW has the ability to scavenge ·OH radicals. GSL-MW also showed a weak 2,2-diphenyl-1-picrylhydrazyl (DPPH; a stable radical)-scavenging activity. Regarding the cytoprotective effects, subconfluent hGFs pretreated with 10× and 100× dilutions of GSL-MW for 3 min and then exposed to harsh environmental conditions, such as pure water or 100 μM H2O2 for 3 min, showed enhanced cell viability rate. Moreover, 10× and 100× dilutions of GSL-MW reduced oxidative damage in confluent hGFs exposed to 12.5 and 25 mM H2O2. Our findings show that GSL-MW has antioxidant potential and cytoprotective effects on hGFs, suggesting that GSL-MW can be used to maintain oral health.

Aryl structural effect on the photoinitiation abilities of aryl glycine derivatives for polymerization upon exposure to blue light

AbstractThe design and development of photoinitiating systems applicable to visible light delivered from light‐emitting diodes (LEDs) have attracted increasing attention owing to the wide application of photopolymerization. In this study, four aryl glycine derivatives are designed and synthesized, and their applicability as visible light‐sensitive photoinitiators is thoroughly investigated. Specifically, the photoinitiation mechanism of these aryl glycine derivatives, when combined with iodonium salt, is investigated using steady‐state photolysis, fluorescence, and electron paramagnetic resonance spin trapping techniques. It is revealed that radicals can be generated from aryl glycine derivatives/iodonium salt combinations upon exposure to blue LEDs (410 and 445 nm) to induce free radical photopolymerization (FRP) of (meth)acrylates. Additionally, besides FRP, a photobase generator based on one of the investigated aryl glycine derivatives is synthesized and demonstrates the capability to initiate epoxy‐thiol polymerization under light irradiation. The remarkable photolatent characteristics demonstrate the significant potential in broadening the application of aryl glycine derivatives in controlled photopolymerization processes.

Effect of Dental Local Anesthetics on Reactive Oxygen Species: An In Vitro Study.

Introduction Oxidative stress, an imbalance between reactive oxygen species (ROS) production and antioxidant defenses, plays an important role in various dental diseases. Local anesthetics are frequently used in dentistry. The potential antioxidant activity of dental local anesthetics can contribute to dental practice. Therefore, this study aimed to investigate the ROS-scavenging activities of three commonly used dental local anesthetics, lidocaine, prilocaine, and articaine, focusing on their effects on hydroxyl radicals (HO•) and superoxide anions (O2 •-). Materials and methods The electron spin resonance (ESR) spin-trapping technique was employed to specifically measure the ROS-scavenging activities of these local anesthetics at varying concentrations. Results Lidocaine, prilocaine, and articaine exhibited concentration-dependent HO•-scavenging activities, with IC50 values of 0.029%, 0.019%, and 0.014%, respectively. Lidocaine and prilocaine showed concentration-dependent O2 •--scavenging activity, with IC50 values of 0.033% and 0.057%, respectively. However, articaine did not scavenge O2 •-. Conclusions The proactive use of dental local anesthetics may mitigate oxidative injury and inflammatory damage through direct ROS scavenging. However, further research is needed to elucidate the specific mechanisms underlying the antioxidant effects of these dental local anesthetics and their potential impact on the dental diseases associated with oxidative stress.

In situ EPR spin-trapping tracking of macroradical formation and the role of a hindered phenol anti-oxidant in reducing thermo-oxidative phenomena of poly(ethylene terephthalate)

One of the major issues concerning poly(ethylene terephthalate) (PET) produced with titanium-based catalysts is its sensitivity to high-temperature oxidation, which results in performance loss and discoloration. Here, the thermo-oxidative phenomena of titanium-catalyst-produced PET during its synthesis and post-processing in the presence of hindered phenol anti-oxidant Irganox 1425 has been investigated by a spin-trapping technique. Three types of spin adducts have been determined and quantified; –O−•CH− is the dominant radical intermediate, while •CH2− and –O−•CH− are mainly produced by the decomposition of diethylene glycol (DEG) units. An excessively high DEG content leads to instability of PET chains at high temperatures and so is not conducive to suppressing oxidation. An anti-oxidant can effectively eliminate radicals induced by thermo-oxidative reactions and improve the thermal stability of PET, especially in the post-processing stage. A comprehensive thermal oxidation mechanism is proposed, in which PET thermolysis starts with hydrogen abstraction to produce –O−•CH−, and then auto-oxidation ensues by radical intermediates attacking other PET chains. The cyclic reaction is reasonably terminated by the anti-oxidant serving as a hydrogen donor to quench radical intermediates.

Photostable selenium-assisted ZnS nanocomposite with efficient visible light photocatalytic activity

Selenium-assisted ZnS nanocomposite has been successfully prepared through a simple soft chemical route and their photocatalytic activity was also investigated for degradation of methylene and rhodamine B dye under ultraviolet and sunlight irradiation. Various surface analysis techniques such as XRD, SEM, TEM, UV-visible, XPS, and photoluminescence were used to analyze the formation of Se/ZnS nanocomposites. XRD studies confirmed the formation of the selenium phase along with ZnS and zinc methacrylate. SEM images showed that ZnS and Se nanoparticles self-aggregated to form three-dimensional spherical nano-assemblies of an average size of about 527 nm. The presence of a different type of defect in Se/ZnS was analyzed from PL spectra. The photocatalytic study revealed the complete degradation of methylene blue in 75 min with a rate constant of 0.073 min−1 under UV light irradiation. In contrast, rhodamine B (RhB) degraded in 90 min with a corresponding rate constant of 0.038 min−1 under the same time duration. Further, this nanocomposite was also efficient under natural sunlight, and almost 85% degradation was achieved after 180 min. Thus, the synergistic effect of strong absorption under UV and visible light source of Se/ZnS nanocomposite minimizes the photogenerated electron-hole pair recombination., which makes them excellent photocatalysts towards the degradation of dyes. Also, this nanocomposite reduced the photo-corrosion under light irradiation and improved photocatalytic stability. In addition, scavenger studies and electron spin resonance in combination with spin trapping technique were used to analyze the contribution of reactive species involved in photocatalysis process.

CORONAVIRUS SARS-COV-2 MODIFIES ANTITUMOR REDOX STATUS OF BLOOD AND INTERCELLULAR MATRIX IN METASTATIC COLORECTAL CANCER PATIENTS (A PILOT STUDY).

The current studies demonstrate that SARS-CoV-2 infection results in increasing complications incidence and the total risk of death in cancer patients. SARS-CoV-2 infection triggers oxidative stress representing one of the major factors of the inflammation contributing to the complicated course of the diseases including cancer. To assess the effect of hypoxia caused by SARS-CoV-2 infection on the redox status of blood in patients with metastatic colorectal cancer (mCRC). 10 patients with SARS-CoV-2, 11 mCRC patients with metachronous liver disease, and 14 mCRC patients with preceding SARS-CoV-2 infection were included in the study. The data on blood biochemistry (C-reactive protein, ferritin, transferrin, and free iron) were analyzed. The levels of superoxide radicals (ROS) in blood cells were determined by electron paramagnetic resonance (EPR) using the spin trap technique. The metalloproteinase activity was measured by polyacrylamide gel zymography with the addition of gelatin as a substrate. In mCRC patients with prior SARS-CoV-2 infection, a 1.26-fold increase in ROS-generating activity of blood neutrophils was observed compared to mCRC patients with no history of SARS-CoV-2 infection. The blood content of C-reactive protein, transferrin, and free iron in mCRC patients with prior SARS-CoV-2 infection increased by 2, 6, and 1.4 times, respectively. The total activity of gelatinases in platelets and neutrophils in the blood of mCRC patients with prior SARS-CoV-2 infection was 1.4 and 1.2 times higher compared to mCRC patients with no history of SARS-CoV-2 infection. mCRC patients with prior COVID-19 have a higher risk of exacerbation of inflammatory reactions. SARS-CoV-2 infection results in redox dіsbalance, which may contribute to the unfavorable course of the disease.

The Influence of Ag+/Ti4+ Ratio on Structural, Optical and Photocatalytic Properties of MWCNT–TiO2–Ag Nanocomposites

In this paper, we propose a simple procedure to obtain multi-walled carbon nanotubes (MWCNTs) decorated with TiO2–Ag nanoparticles (MWCNT–TiO2–Ag). The MWCNTs were decorated with TiO2–Ag via combined functionalization with –OH and –COOH groups and a polymer-wrapping technique using poly(allylamine)hydrochloride (PAH). TiO2-modified Ag nanoparticles were synthesized via the Pechini method using a mixture of acetylacetonate-modified titanium (IV) isopropoxide with silver nitrate (with Ag+/Ti4+ atomic ratios of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) and L(+)-ascorbic acid as reducing agents. XRD analysis revealed the formation of nanocomposites containing CNT, anatase TiO2, and Ag. The presence of nanoparticles on the MWCNT surfaces was determined using TEM. The morphology of the TiO2–Ag nanoparticles on the MWCNT surfaces was also determined using TEM. UV–Vis investigations revealed that an increase in the ratio between Ag+ and Ti4+ decreased the band gap energy of the samples. The characteristic vibrations of the TiO2, Ag, and C atoms of the graphite were identified using Raman spectroscopy. The photocatalytic activity of the MWCNT–TiO2–Ag nanocomposite was assessed by examining the degradation of Allura Red (E129) aqueous solution under UV irradiation. The dye photodegradation process followed a pseudo-first-order kinetic with respect to the Langmuir–Hinshelwood reaction mechanism. The spin-trapping technique evidenced that •O2− was the main species generated responsible for the Allura Red degradation.

Dietary Magnesium Deficiency in Rats Enhances Free Radical Production in Skeletal Muscle

Recent studies suggest that free radicals may be involved in tissue injuries induced by magnesium deficiency. The aim of the present study was to assess the effect of magnesium deficiency on free radical production of skeletal muscle tissue. Male Wistar rats were pair-fed from weaning for 12 d either control or Mg-deficient diets containing 960 or 40 mg magnesium/kg diet, respectively. In the Mg-deficient rats, hypomagnesemia was accompanied by significantly lower magnesium and greater calcium concentrations in skeletal muscle tissue. Electron microscopy of skeletal muscle tissue revealed ultrastructural changes, including swelling mitochondria and disorganization of the sar-coplasmic reticulum network. Using the spin-trapping technique, we showed that significantly more hydroxyl radicals were generated in muscle homogenates of Mg-deficient rats. Moreover, the amount of spin trap adducts was increased in the presence of exogenous iron in both groups. In agreement with these observations, a greater concentration of thiobarbituric acid-reactive substances and a lower concentration of thiol groups were found in skeletal muscle of the Mg-deficient group compared with controls. These results strongly support the hypothesis that free radical-mediated injury could contribute to skeletal muscle lesions resulting from magnesium deficiency.

Undiscovered Spin Trapping Artifacts in Persulfate Oxidation Processes: Implications for Identification of Hydroxyl or Sulfate Radicals in Water

Electron paramagnetic resonance (EPR) coupled with the spin trapping technique is widely used to identify radicals and has become a tool that is being heavily relied on to probe the reaction mechanism in advanced oxidation processes (AOPs). However, the unexpected spin trapping artifacts in a highly oxidizing environment may mislead the mechanistic interpretations of AOPs. Here, we report previously unrevealed reactions between peroxydisulfate (PDS) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or N-tert-butyl-α-phenylnitrone (PBN). The mainly detectable adducts are attributed to DMPO-OH and PBN-OH. Through radical quenching experiments, the nonradical generation pathways of DMPO-OH and PBN-OH are validated, and the 17O incorporation experiment demonstrates that H2O plays a critical role in DMPO-OH production. The formation routes of the primary artifact signals (DMPO-OH, DMPO-SO4, PBN-OH, and PBN-SO4) are further proposed by applying diverse solvents. PDS may directly oxidize DMPO to generate DMPO-SO4 in acetonitrile or acetone solvent, while DMPO-OH is yielded using H2O as the solvent. The generation of PBN-OH or PBN-SO4 follows the inverted spin trapping mechanism (a combination of one-electron oxidation and nucleophilic addition). These findings manifest the necessity of selecting the proper spin traps and performing careful control tests during exploration of the catalytic oxidation mechanism under highly oxidizing conditions.

Albumin-Functionalized Iron Oxide Nanoparticles for Theranostics: Engineering and Long-Term In Situ Imaging.

Magnetic nanosystems (MNSs) consisting of magnetic iron oxide nanoparticles (IONPs) coated by human serum albumin (HSA), commonly used as a component of hybrid nanosystems for theranostics, were engineered and characterized. The HSA coating was obtained by means of adsorption and free radical modification of the protein molecules on the surface of IONPs exhibiting peroxidase-like activity. The generation of hydroxyl radicals in the reaction of IONPs with hydrogen peroxide was proven by the spin trap technique. The methods of dynamic light scattering (DLS) and electron magnetic resonance (EMR) were applied to confirm the stability of the coatings formed on the surface of the IONPs. The synthesized MNSs (d ~35 nm by DLS) were intraarterially administered in tumors implanted to rats in the dose range from 20 to 60 μg per animal and studied in vivo as a contrasting agent for computed tomography. The long-term (within 14 days of the experiment) presence of the MNSs in the tumor vascular bed was detected without immediate or delayed adverse reactions and significant systemic toxic effects during the observation period. The peroxidase-like activity of MNSs was proven by the colorimetric test with o-phenylenediamine (OPD) as a substrate. The potential of the synthesized MNSs to be used for theranostics, particularly, in oncology, was discussed.

(Invited) Operando EPR Study on Radicals in Anion-Exchange Membrane Fuel Cells

In the rapidly developing modern society, there is an urgent need for the wide-ranging availability of advanced and eco-friendly energy sources. One of the possible alternatives is the application of anion exchange membrane fuel cells (AEMFCs) with a catalyst reducing dioxygen efficiently. These promising devices can revolutionize the energy sector since they practically produce no pollution. However, to make them more widely used, several obstacles must be overcome. As a result, vast-ranging investigations focus on improving the properties of conductive polymer membranes [1] and catalysts for the oxygen reduction reaction (ORR) [2]. The durability of the membrane electrode assembly (MEA) is one of the critical requirements for the successful commercialization of anion exchange membrane fuel cells (AEMFCs). Despite significant impacts of nucleophilic degradation on ion-exchange capability and the anionic conductivity of investigated membranes, it is believed to affect only cationic sites of membrane polymers and thus cannot explain the reported loss in the mechanical strength of degraded AEMs. Such a phenomenon might be related to polymer backbone degradation caused by free radicals. This was widely described in the literature in the case of fuel cells using proton-conducting membranes [3] but barely mentioned for AEMFCs [4]. Since the oxidative degradation of hydrocarbon polymers is very well known, we aimed to comprehensively investigate the formation of the short-lived species generated during the operation of AEMFCs as well as stable radicals present in the polymer membranes.We investigated the LDPE-base membranes with Pt black, Pd black, PdAg, and Ag as the ORR catalysts, whereas for HOR the Pt black, Pd black, and NiFe catalysts were used. The in-situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals was monitored by the EPR spin trapping technique. In Figure 1 the EPR spectra of DMPO spin adducts trapped during operation of micro-fuel cell placed in EPR spectrometer cavity are presented. In this experiment, the LDPE-base membrane with platinum catalysts on both sides was used. The main detected adducts during the operation of the micro-AEMFC were DMPO-OOH and DMPO-OH on the cathode side and DMPO-H on the anode side. Additionally, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation [5]. Preliminary results suggest that the creation of the short-living radicals during AEMFCs operation is independent of the used membrane. However, the applied catalysts determine the number of detected radicals. The EPR investigations indicate that, in addition to the known chemical degradation mechanisms of the cationic ammonium groups of the membrane, oxidative degradation, including radical reactions, has to be taken into account when the stability of an anion conductive polymer for AEMFCs is investigated. The formation of stable radicals in AEMs was proven for the first time in this study. All short-living radicals formed during the AEMFC operation were fully identified. The presence of radicals in the AEM after AEMFC testing indicates that reactive oxygen species may play a very important role in the degradation mechanism of the anion conducting polymers. Results from this study shed light on the understanding of radical formation and presence in the membranes during AEMFC tests, which in turn may help to solve the challenge of anion exchange membrane stability. Acknowledgments. This work was supported by the Polish National Science Centre (NCN) project OPUS-14, No. 2017/27/B/ST5/01004.

Highly stable MWCNT-CoFe2O4 photocatalyst. EGA-FTIR coupling as efficient tool to illustrate the formation mechanism

MWCNT-CoFe2O4 nanocomposites were prepared in sequential synthesis steps by decorating CoFe2O4 nanoparticles on the surface of functionalized MWCNT. Initially, the CoFe2O4 nanoparticles were obtained by chemical precipitation and subsequently, the obtained CoFe2O4 nanoparticles were anchored on functionalized MWCNT through polymer wrapping. The thermal analysis approaches namely, evolved gas analysis (EGA) coupled with FT-IR spectra were involved in highlighting the sequential steps mechanism for obtaining MWCNT-CoFe2O4 nanocomposites. The composite formation was proved by X-ray Diffraction (XRD), Scanning Transmission Electron Microscopy (STEM), FT-IR spectroscopy, X-ray Photoelectron Spectroscopy (XPS). The influence of CoFe2O4 content on the magnetic and textural properties (surface area and porosity measurements) of the obtained nanocomposites was evidenced. Depicting the importance of thermal stability of nanomaterials in different industrial applications, the thermal behavior of MWCNT and CoFe2O4 was pointed out. Furthermore, the photocatalytic activity against organic pollutants such as Rhodamine B (RhB) and oxytetracicline (OTC) were evidenced. Additionally, it was evidenced that the MWCNTs acquired ferromagnetic behavior through spin polarized electron transfer from the CoFe2O4. The electron spin resonance spectroscopy (ESR) coupled with spin trapping technique was used to evidence the generation of reactive oxygen species (ROS). The obtained results suggest the efficient anchoring of CoFe2O4 on MWCNT through polymer linkage resulting in a thermal stable magnetic recoverable photocatalyst. The photocatalytic mechanism was discussed in terms spin polarized transitions and ROS generation. During the irradiation superoxide anion (O2-), hydroxyl (•OH) radical and nitroxide were detected.

Heating of consumer cannabis oils can lead to free radical initiated degradation, causing CBD and THC depletion

Commercial cannabis oil products are widely available in Canada even though there is a significant gap in scientific information regarding them. Oils, such as vegetable oils, are known to undergo oxidative changes through free radical mechanisms when they are heated or aged, but the cannabis oils used in this study did not have expiry dates or best-before usage dates. This led to the question of how these products would be affected with time. We hypothesized that cannabis oils would produce increased concentrations of free radicals in aging-simulated conditions, which would be related to a decrease in cannabidiol (CBD) or Δ9-tetrahydrocannabinol (THC) content.Cannabis oils and their respective vehicles (oils) were heated using two protocols: One (moderate aging method) used a 2-day heating protocol at 50 °C, and the other (enhanced aging method) used a 14-day heating protocol at 70 °C. We used electron paramagnetic resonance (EPR) spectroscopy for free radical analysis using the spin trapping technique using 200 mM PBN and 0.02 mM CuCl2 (for peroxide breakdown to free radicals). For active ingredient analysis (CBD, THC), we used LC/MS.Cannabis oils that contained unsaturated oils as their vehicles, such as olive or sunflower oil, all showed varying degrees of free radical formation. In both aged and unaged oils containing CBD or THC, less free radical formation was detected compared to the vehicle controls. Cannabis oils using medium-chain triglycerides (MCT) showed little or no free radical formation. The most significant decrease in CBD or THC was observed in the products using sunflower oil, to a lesser extent in MCT oil, and THC also decreased in olive oil.These findings are important for consumers and policymakers considering using such products in hot beverages or cooking and highlighting the importance of appropriate storage conditions.

Symmetrically-substituted Thiazolo[5,4-d]thiazole derivatives as both photoinitiators and dyes for 3D printing under violet LED

The outstanding photochemical properties of thiazolothiazole and its derivatives make them attractive as potential photoinitiators. Two homosubstituted thiazolo[5,4-d]thiazole derivatives, 2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole and 2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole, were investigated as photoinitiators for both the free radical and the cationic polymerization upon the light irradiation from LED@410 nm. In particular, steady-state photolysis, fluorescence quenching experiments, and electron paramagnetic resonance spin-trapping techniques were used to study their photochemical mechanisms in generating active species. When coupled with one or two additives, these thiazolothiazole-based photoinitiating systems showed effective photoinitiation abilities on both the free radical and the cationic photopolymerization. Specifically, 2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole- and 2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-based photoinitiating systems were found to be of similar efficiency on the free radical photopolymerization of trimethylolpropane triacrylate and the dental resin (the blend of bisphenol A glycidyl methacrylate and triethylene glycol dimethacrylate) with minor shrinkage but presented different performance in cationic photopolymerization of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate. Moreover, the curing depth of the samples and 3D printing capability were also investigated to determine their potential applications.

Multifunctional Ag/AgCl/ZnTiO3 structures as highly efficient photocatalysts for the removal of nitrophenols, CO2 photoreduction, biomedical waste treatment, and bacteria inactivation

Over the past few decades, biological hazards and organic pollution have become major environmental concerns. Photocatalysis has been found to be effective in minimizing the negative impacts of these issues in air and water. Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method, including hydrothermal and coprecipitation. The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach. The prepared photocatalysts offered excellent nitrophenol mineralization (>90%) after 90 min of visible light irradiation. Based on the spin-trapping ESR technique, •O2̅– was recognized as the eminent reactive species during the photocatalytic process. Interestingly, the plasmonic Ag/AgCl/ZnTiO3 photocatalyst presented promising CO2 to CO/CH4 conversion with a production rate of 95.0/18.5 μmol.g−1.h−1 under visible light irradiation, which is about 1.6 times higher than that of ZnTiO3, implying the synergetic effects due to Ag/AgCl in the ternary construction. In addition to the investigation of antibacterial activity, the prepared photocatalysts were successfully applied to treat the hazardous biological waste bearing U87-MG cancer cells under visible light for the first time. Several as-related analytical techniques were served to demonstrate the activity and interaction pathways. This work may hone a new insight into designing highly efficacious ternary photocatalytic materials.

Facile synthesis of MWCNT-WO3 composites with enhanced photocatalytic degradation of methylene blue dye

Multi-walled carbon nanotube-tungsten oxide (MWCNT-WO3) nanocomposites corresponding to different weight ratios of the two composite components MWCNT:WO3 were prepared by using a facile synthesis procedure and tested as photocatalysts activated by UV light for degradation of synthetic methylene blue (MB) solution. The composites were characterized by XRD, TEM, SEM, FTIR, UV–VIS, PL and TGA. The average crystallite size of WO3 calculated from XRD patterns was around 45 nm for all synthesized samples. TEM and SEM images confirmed the attachment of polyhedral WO3 nanoparticles on the MWCNTs surface. TGA results showed an enhanced thermal stability of the MWCNT-WO3 composites with increased content of WO3. Photocatalytic experiments proved that the use of MWCNTs offered a notable increase of the photocatalytic performance of WO3 in degradation of MB dye. The optimum MWCNT-W-7 composite exhibited 87 % MB degradation efficiency. The types of ROS generated by the composites were determined using EPR spectroscopy coupled with spin trapping technique. These results suggested that hydroxyl radicals were the main species involved in the photodegradation process of MB dye.

Role of Human Aldehyde Oxidase in the Generation of Reactive Oxygen Species during the Metabolism of Nicotine

Nicotine is the major addictive constituent of tobacco and alternative tobacco products including electronic cigarettes (e‐cigs). While e‐cig vaping has been proposed as safer than traditional tobacco smoking, recent studies has demonstrated that these products can also trigger oxidant stress and inflammation with resultant pulmonary and cardiovascular disease. E‐cig liquids contain high levels of nicotine typically of 12 to 24 mg/ml or more and with the use of high power delivery devices high, poorly controlled levels of nicotine can be delivered. When inhaling tobacco cigarette smoke or e‐cig vape, nicotine is rapidly absorbed through the lungs. The major pathway of nicotine metabolism in humans consists of the C‐oxidation of nicotine to produce cotinine involving a two‐step process: the first step is CYP2A6‐catalyzed 5′‐oxidation to nicotine‐Δ1′(5′)‐iminium ion (NI), which is in equilibrium with 5′‐hydroxynicotine; and the second step is aldehyde oxidase (AO) catalyzed oxidation of NI to cotinine.Using both cytochrome‐c reduction and EPR spin trapping techniques, we show for the first time that the oxidation of NI by human AO produces superoxide radical anion (O2• −) with high flux rates. Purified recombinant human AO (hAO) was prepared and characterized by SDS gel electrophoresis and optical absorption spectroscopy. hAO, 40 nM was incubated in the presence of NI concentrations from 1‒50 µM. The kinetic parameters, Km and Vmax values, for superoxide generation from NI were determined to be 2.7 ± 0.4 μM and 694 ± 24 nmol min−1 mg−1 of protein, respectively. From quantitation of the measured superoxide and the amount of NI consumed, we estimate that ~60% of the oxygen consumed in this process is converted to superoxide with ~40% hydrogen peroxide. Superoxide generation was almost completely quenched by either 0.5 μM raloxifene, a potent inhibitor of AO, or 0.1 μM Copper‐Zinc‐superoxide dismutase (SOD1) with no superoxide generation detected either in the absence of either AO or nicotine‐Δ1′(5′)‐iminium ion.Therefore, human AO efficiently catalyzes the oxidation of NI to cotinine with concomitant production of reactive oxygen species. Due to the high expression levels of AO in lung tissue as well as its rapid rate of NI metabolism with low Km, AO rapidly and efficiently converts NI to cotinine with the formation of superoxide and hydrogen peroxide. Thus, nicotine metabolism will be associated with the formation of superoxide, hydrogen peroxide and secondary reactive oxygen species that can in turn cause lung oxidative stress and inflammation.

Effects of Acidity on Reactive Oxygen Species Formation from Secondary Organic Aerosols.

Reactive oxygen species (ROS) play a critical role in the chemical transformation of atmospheric secondary organic aerosols (SOA) and aerosol health effects by causing oxidative stress in vivo. Acidity is an important physicochemical property of atmospheric aerosols, but its effects on the ROS formation from SOA have been poorly characterized. By applying the electron paramagnetic resonance spin-trapping technique and the Diogenes chemiluminescence assay, we find highly distinct radical yields and composition at different pH values in the range of 1–7.4 from SOA generated by oxidation of isoprene, α-terpineol, α-pinene, β-pinene, toluene, and naphthalene. We observe that isoprene SOA has substantial hydroxyl radical (•OH) and organic radical yields at neutral pH, which are 1.5–2 times higher compared to acidic conditions in total radical yields. Superoxide (O2•–) is found to be the dominant species generated by all types of SOAs at lower pH. At neutral pH, α-terpineol SOA exhibits a substantial yield of carbon-centered organic radicals, while no radical formation is observed by aromatic SOA. Further experiments with model compounds show that the decomposition of organic peroxide leading to radical formation may be suppressed at lower pH due to acid-catalyzed rearrangement of peroxides. We also observe 1.5–3 times higher molar yields of hydrogen peroxide (H2O2) in acidic conditions compared to neutral pH by biogenic and aromatic SOA, likely due to enhanced decomposition of α-hydroxyhydroperoxides and quinone redox cycling, respectively. These findings are critical to bridge the gap in understanding ROS formation mechanisms and kinetics in atmospheric and physiological environments.

The regularity of heat-induced free radicals generation and transition of camellia oil

In this study, the radicals formed in camellia oil upon a heating process were identified and quantified using Electron Spin Resonance (ESR) spectroscopy coupled with spin-trapping technique. PBN and DMPO were served as spin traps. The total amounts of free radicals of heated camellia oil showed an increasing trend with the extension of heating time at 140 °C, 150 °C and 160 °C. In accordance with hyperfine splitting constants (aN, aH) ─ the crucial parameter for identifying free radical species ─ of free radical, it was definitely confirmed that alkyl, alkoxyl, oxygen-centered and DMPO oxidate free radicals were present in heated camellia oil. A free radical transition pathway was proposed that alkyl free radical is initially generated, then, alkyl peroxy free radical is subsequently generated in the presence of oxygen which eventually shifts into alkoxyl free radical by means of an intermediate formed from H-capture reaction of alkyl peroxy free radical.

Spectroscopic and Morpho-Structural Characterization of Copper Indium Disulfide–Zinc Oxide Nanocomposites with Photocatalytic Properties

CuInS2–ZnO nanocomposites were prepared by two combined approaches, namely solvothermal and chemical precipitation. The structure, morphology, composition and optical properties of the nanocomposites was studied by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). The influence of ZnO content on the photocatalytic activity of these nanocomposites was studied. The results showed that CuInS2-ZnO samples possess photocatalytic activity against a Rhodamine B (RhB) synthetic solution. Additionally, electron spin resonance spectroscopy (ESR) coupled with spin trapping technique was used to characterize the reactive oxygen species (ROS). The photocatalytic mechanism was discussed according to ROS generation that were able to degrade the RhB. The photodegradation rate for RhB removal by CuInS2–ZnO nanoparticles increased with the addition of ZnO nanoparticles on their surface. During the irradiation, both hydroxyl radical (OH−) and superoxide anion (O2 −) were highlighted suggesting that the CuInS2–ZnO nanocomposites are suitable for use in water depollution by photocatalysis.