Radical Signal Intensity Research Articles

The Interaction of Myeloperoxidase with the Industrial Contaminant 6-PPD: A Potential Pathway for Reactive Metabolites.

6-PPD (N-[1,3-dimethylbutyl]-N'-phenyl-p-phenylenediamine) is an industrial antioxidant reported to be an environmental contaminant. It was found to be highly toxic to coho salmon and potentially other aquatic organisms. The toxicity of 6-PPD in humans, however, remains unknown. The neutrophil enzyme myeloperoxidase (MPO) is known to catalyze xenobiotic metabolism; therefore, its role in 6-PPD cytotoxicity was investigated using the MPO-rich HL-60 cell line. UV-visible spectroscopy and liquid chromatography-mass spectrometry (LC/MS) were performed to investigate the MPO-mediated oxidation of 6-PPD and identify possible metabolites in the absence and presence of glutathione (GSH). 6-PPD's cytotoxicity, effect on mitochondrial membrane potential (MMP), and GSH-depleting ability in HL-60 cells were assessed. Electron paramagnetic resonance (EPR) was used to determine GSH radical formation using DMPO, and mitochondrial-derived superoxide was assessed with the mito-TEMPO-H probe. Evaluation of the 6-PPD-induced cellular injury pathways was performed by preincubating an antioxidant and an MPO inhibitor with HL-60 cells. UV-vis analysis of MPO-catalyzed oxidation of 6-PPD demonstrated changes in the 6-PPD spectrum, whereas the addition of GSH altered the spectrum, indicating possible GSH conjugate formation. LC/MS showed the formation of multiple products, including GSH-6-PPD conjugates and a GSH conjugate to a 4-hydroxydiphenylamine (a known 6-PPD degradant), which could potentially induce cytotoxicity. 6-PPD demonstrated concentration-dependent cytotoxicity, and cellular GSH levels were decreased by 6-PPD. Similarly, the level of MMP decreased, suggesting mitochondrial depolarization. Furthermore, the EPR spin probe for mitochondrial superoxide showed a positive relationship with 6-PPD concentration, and EPR spin-trapping demonstrated 6-PPD concentration-dependent GSH radical signal intensity using MPO/H2O2. The GSH precursor, NAC, demonstrated partial cytoprotection against 6-PPD; however, the MPO inhibitor PF-1355 surprisingly showed no significant cytoprotective effect. Our results suggest that MPO could be a potential catalyst for 6-PPD toxicity in humans. However, MPO inhibition did not significantly affect cellular viability, suggesting an MPO-independent toxicity pathway. These findings warrant a deeper investigation to determine 6-PPD mammalian toxicity pathways.

Schottky Barrier-Based Built-In Electric Field for Enhanced Tumor Photodynamic Therapy.

Photodynamic therapy's antitumor efficacy is hindered by the inefficient generation of reactive oxygen species (ROS) due to the photogenerated electron-hole pairs recombination of photosensitizers (PS). Therefore, there is an urgent need to develop efficient PSs with enhanced carrier dynamics. Herein, we designed Schottky junctions composed of cobalt tetroxide and palladium nanocubes (Co3O4@Pd) with a built-in electric field as effective PS. The built-in electric field enhanced photogenerated charge separation and migration, resulting in the generation of abundant electron-hole pairs and allowing effective production of ROS. Thanks to the built-in electric field, the photocurrent intensity and carrier lifetime of Co3O4@Pd were approximately 2 and 3 times those of Co3O4, respectively. Besides, the signal intensity of hydroxyl radical and singlet oxygen increased to 253.4% and 135.9%, respectively. Moreover, the localized surface plasmon resonance effect of Pd also enhanced the photothermal conversion efficiency of Co3O4@Pd to 40.50%. In vitro cellular level and in vivo xenograft model evaluations demonstrated that Co3O4@Pd could generate large amounts of ROS, trigger apoptosis, and inhibit tumor growth under near-infrared laser irradiation. Generally, this study reveals the contribution of the built-in electric field to improving photodynamic performance and provides new ideas for designing efficient inorganic PSs.

Genome-Centric Metatranscriptomic Characterization of a Humin-Facilitated Anaerobic Tetrabromobisphenol A-Dehalogenating Consortium.

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in electronics manufacturing, has caused global contamination due to improper e-waste disposal. Its persistence, bioaccumulation, and potential carcinogenicity drive studies of its transformation and underlying (a)biotic interactions. This study achieved an anaerobic enrichment culture capable of reductively dehalogenating TBBPA to the more bioavailable bisphenol A. 16S rRNA gene amplicon sequencing and quantitative PCR confirmed that successive dehalogenation of four bromide ions from TBBPA was coupled with the growth of both Dehalobacter sp. and Dehalococcoides sp. with growth yields of 5.0 ± 0.4 × 108 and 8.6 ± 4.6 × 108 cells per μmol Br- released (N = 3), respectively. TBBPA dehalogenation was facilitated by solid humin and reduced humin, which possessed the highest organic radical signal intensity and reducing groups -NH2, and maintained the highest dehalogenation rate and dehalogenator copies. Genome-centric metatranscriptomic analyses revealed upregulated putative TBBPA-dehalogenating rdhA (reductive dehalogenase) genes with humin amendment, cprA-like Dhb_rdhA1 gene in Dehalobacter species, and Dhc_rdhA1/Dhc_rdhA2 genes in Dehalococcoides species. The upregulated genes of lactate fermentation, de novo corrinoid biosynthesis, and extracellular electron transport in the humin amended treatment also stimulated TBBPA dehalogenation. This study provided a comprehensive understanding of humin-facilitated organohalide respiration.

Inhibitory Effect of Tamarix ramosissima Extract on the Formation of Heterocyclic Amines in Roast Lamb Patties by Retarding the Consumption of Precursors and Preventing Free Radicals.

Tamarix ramosissima has been widely used as barbecue skewers for the good taste and unique flavor it gives to the meat, but the effects of T. ramosissima on heterocyclic amine (HA) formation in roast lamb are unknown. The influence of T. ramosissima extract (TRE) on HA formation, precursors’ consumption, and free radicals’ generation in roast lamb patties were elucidated by UPLC-MS, HPLC, and electron spin resonance (ESR) analysis, respectively. Six HAs were identified and compared with the control group; the total and polar HAs decreased by 30.51% and 56.92% with TRE addition at 0.30 g/kg. The highest inhibitory effect was found against 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP) formation (70.83%) at 0.45 g/kg. The addition of TRE retarded the consumption of HA precursors, resulting in fewer HAs formed. The typical signal intensity of free radicals in roast lamb patties significantly decreased with TRE addition versus the control group (p < 0.05), and the higher the levels of the TRE, the greater the decrease in signal intensity. We propose that the inhibitory effects of TRE on HA formation, especially on polar HAs, were probably achieved by retarding the consumption of precursors and preventing free radicals from being generated in roast lamb patties. These findings provide valuable information concerning TRE’s effectiveness in preventing HA formation through both the precursor consumption and free radical scavenging mechanisms.

Monitoring the lipid oxidation and flavor of Russian sturgeon fillets treated with low temperature vacuum heating: formation and relationship.

Sturgeon is one of the most precious fish resources worldwide. Low temperature vacuum heating (LTVH) has been confirmed as a good way of maintaining food quality. However, there is a lack of in-depth studies assessing the impact of LTVH on lipid oxidation and flavor formation. The present study compared the effect of LTVH and traditional cooking on lipid oxidation and flavor of sturgeon fillets. In total, 13 fatty acids were detected, of which polyunsaturated fatty acids content was the highest (P < 0.05). LTVH prevented the formation of conjugated diene and thiobarbituric acid reactive substances (P < 0.05), as manifested by an increased signal intensity of free radicals of electron spin resonance. The characteristic peaks intensity of lipid by Raman at 970 cm-1 , 1080 cm-1 and 1655 cm-1 were reduced, whereas peaks at 1068 cm-1 and 1125 cm-1 displayed the opposite trend. Confocal fluorescence microscopy showed that the lipids particles were reduced and distributed more evenly with an increase in heating temperature. Principal component analysis of electronic nose cannot effectively separate all groups; however, gas chromatography-ion migration spectrometry showed that the volatile flavor compounds were relatively stable during LTVH. Correlation analysis of all the above lipid oxidation indices and characteristic flavor substances showed that each treatment group was located in different quadrants and demonstrated great differentiation. Overall, the results of the present study support the view that LTVH is a healthier way of cooking. © 2022 Society of Chemical Industry.

Products of Prolonged Autoxidation of Simple Dihydric Phenols in the Presence of Copper(II) Ions – An Electron Spin Resonance Study

Electron spin resonance (ESR) spectroscopy was used for characterizing the products obtained by prolonged autoxidation of simple dihydric phenols (hydroquinone, catechol, and 4-methylcatechol) in the presence of copper(II) ions. Room temperature ESR spectra revealed that both paramagnetic copper(II) ions and organic radicals are present in obtained autoxidation products similarly to the humic acid complexed copper(II) ions. The ratio of organic radical signal intensity to the copper(II) ion signal intensity suggests that the smallest amount of copper(II) ions is incorporated in the hydroquinone autoxidation product while the highest amount of copper(II) ions is incorporated in the autoxidation product of catechol. Satisfactory computer simulations of experimental ESR spectra were obtained by considering only one type of copper(II) ion binding site for hydroquinone autoxidation product and two distinct types of copper(II) ion binding sites for catechol and 4-methylcatechol autoxidation products. Parameters obtained by the computer simulation of ESR spectra indicated prevalent ionic bonding of copper(II) ions in polymeric matrices with tetrahedral distortion at copper(II) ion binding sites and negligible exchange interactions between them. Products obtained by the hydroquinone and catechol autoxidation have more similar characteristics in comparison to the product obtained by the 4-methylcatechol autoxidation where more expressed ionic bonding of copper(II) ions, and smaller tetrahedral distortion are present. Due to the dipolar interactions of oxygen-centered organic radicals in autoxidation products with paramagnetic copper(II) ions, their ESR linewidths are larger and g-values smaller in comparison to the values found in humic acids from various soil types.

Effect of unsaturated fatty acids on glycation product formation pathways

Glycation and lipid oxidation in high-nutrient foods are closely related and exhibit complex interactions. To evaluate the effect of unsaturated fatty acids (UFAs) on glycation pathways, glycation products in glucose-lysine-UFA models were detected by ultra performance liquid chromatography-tandem mass spectrometry and electron spin resonance spectroscopy, together with multivariate data analysis. Results indicated that UFAs inhibited glucose oxidation by decreasing the contents of carbonyl compounds about 73.85–86.19%. UFAs promoted the formation of glycation products mainly via production of active radical. In three models, linoleic acid (LA) exhibits stronger glycation activity than oleic acid and eicosapentaenoic acid. LA significantly promoted radical formation, as well as the formation and degradation of fructosyllysine (FL), the signal intensity of active radical increased 647.45% and FL increased 78.73%. The comparison of E(k3), E(k7) and variable importance in projection values of orthogonal projections to latent structures discriminant analysis in three models also proved these conclusions. By studying the characteristics of LA on glycation in three UFA, we hypothesized that unsaturation is not the key factor in evaluating their effects on glycation, the radical activity, UFA solubility, spatial structure and interaction should be considered as potentially important factors.

Effects of ammonia addition on soot formation in ethylene laminar diffusion flames

In light of the increasingly stringent pollutant emission regulation and energy crisis, ammonia (NH3) has been regarded as a highly competitive alternative fuel. Previous studies mainly focused on the fundamental combustion characteristics and NOx emission of co-firing NH3 with hydrocarbons; however, soot emission was rarely studied. In this study, effects of NH3 addition with varying ratios (between 0% and 60% by mole fraction while the remainder is argon) on soot formation in ethylene (40% by mole fraction) laminar diffusion flames were experimentally and numerically investigated. Two-color laser induced incandescence and planar laser induced fluorescence method were used to measure the spatial distributions of soot volume fraction, polycyclic aromatic hydrocarbons (PAHs), and OH radical. Temperature profiles along the flame centerline were obtained through rapid thermocouple insertion technique. Results show that with NH3 addition, the flame height increases and the temperature at the same height decreases. Peak concentration and total loading show that the inhibitory effect of NH3 addition on PAHs and soot volume fraction (SVF) is in the order: A1 < A2&A3 < A4 < SVF. The primary particle size obtained by transmission electron microscope substantially decreases with the increasing NH3. In addition, the signal intensity of OH radical was diminished, indicating that instead of promoting the soot oxidation, NH3 reduces soot formation by inhibiting PAH growth, soot inception, and surface growth. Chemical kinetic analysis suggests that NH3 addition reduces the concentrations of H, C2H2, and C3H3, thus markedly inhibiting the rate-limiting step of A1 formation and PAH growth.

Molecular level changes during suppression of Rhizoctonia solani growth by humic substances and relationships with chemical structure

Elucidation of the inhibitory effects of humic substances (HSs) on phytopathogenic fungi and the underlying molecular mechanisms are highly important for improved biocontrol. In this study, we investigated the growth suppression, morphological characteristics, transcriptomic sequence, and radical signals of Rhizoctonia solani following HS addition (50 mg/L). Through mycelial cultured experiment, mycelia growth of R. solani had been suppressed with HS addition, and the inhibition rate was 24.88 ± 0.11% compared to the control. Field emission-scanning electron microscopy showed increased and superimposed branching mycelial growth, with a shriveled appearance. RNA samples of R. solani cultured with or without HSs were both extracted to examine the sequence on molecular level by Illumina HiSeq sequencing platform. RNA sequencing analysis revealed 175 differentially expressed genes (DEGs; 111 upregulated and 64 downregulated) between the HSs treatment and control. The upregulated unigenes were annotated and significantly enriched to three molecular processes: vitamin B6 metabolism, ABC transporters, and glutathione metabolism, while the downregulated unigenes were annotated to carbohydrate metabolism, but not significantly enriched. Real time-quantitative polymerase chain reaction analysis showed that the unigenes related to hexokinase, glucose-6-phosphate isomerase, glutathione synthase, and glutathione reductase were significantly decreased (by 60.03%, 70.70%, 60.33%, and 57.59%, respectively), while those related to glutathione S-transferase were significantly increased (2.66-fold). The electron paramagnetic resonance spectra showed that HSs induced increased the intensity of radical signals of R. solani in a cultured system increased by 59.56% compared to CK (without HSs addition). Network analysis based on DEGs expression and the chemical structure of HSs revealed that the carbonyl moiety in HSs formed the most links with nodes of the DEGs (sum of the links of positive and negative effects = 70), implicating this structure as the active fraction responsible for the inhibitory effect. This study provides molecular and chemical evidence of the biofungicidal activity of HSs with the potential for practical application.

Novel strategy of using a C/C electrodes electro-activated peroxymonosulfate to remove NO from simulated flue gas

Simultaneous treatment NO and SO2 from industrial flue gas by wet processes, a large number of sulfate (SO42-) ions will be generated in the system, and SO42- ion is corrosive to concrete buildings used for subsequent sewage treatment. If the generated SO42- ions can be in-situ reutilization to be converted to sulfate radicals (SO4·-) with strong oxidizing, then they can continue to oxidize removal NO and SO2 in the flue gas, which will further promote the effect of flue gas treatment. Therefore, a novel strategy with C/C electrodes electro-activated peroxymonosulfate (PMS) is developed, utilizing electrons to activate PMS to generate radicals while carbon electrodes converting SO42- ions to SO4·- radicals via direct electron transfer, and then use the radicals and other active substance generated to remove NO. The effects of current intensity, temperature on NO removal and the types of oxides produced in the electro-activated system are investigated. In addition, the relationships of current intensity and conversion time with the SO4·- radical signal intensity detected are discussed respectively. Accordingly, a catalytic mechanism is proposed involving SO4·-⋅OH and 1O2 radicals oxidation and C-PMS* non-radical oxidation.

Plant derived ingredients rich in nitrates or phenolics for protection of pork against protein oxidation

A pork model system containg phenolic extracts (citrus, rosemary, and acerola), traditional Spanish food ingredients (paprika, garlic, and oregano), or natural nitrate sources (beet, lettuce, arugula, spinach, chard, celery, and watercress) were oxidized by an hydrophilic (OXHydro, 2,2'-azobis(2-amidinopropane)-dihydrochloride; AAPH) or lipophilic (OXLip, 2,2'-azobis(2,4-dimethylvaleronitrile; AMVN) radical initiator. Citrus as well as lettuce and spinach protected almost fully against protein thiol loss and showed efficient radical scavenging activity as determined by ESR spectroscopy in both oxidizing systems. Rosemary was an efficient radical scavenger in both systems, but behaved as a prooxidant on thiols in the OXHydro system. Acerola was also found to be prooxidative as determined by increased radical signal intensity especially in the OXLip system, assigned to high concentration of ascorbate in the extract. Natural nitrate sources, especially lettuce and spinach, are accordingly potential substitutes for synthetic phenolic antioxidants protecting against protein thiol oxidation and radical formation in pork.

Effect of Decabromodiphenyl Ether on Free Radicals in the Degradation of P-nitrophenol under Ultraviolet Light

Polybrominated diphenyl ether as an additive bromine flame retardant is widely used in industrial products, due to its strong fat-soluble and biological accumulating, it is a new type of ecological risk of environmental organic pollutants, and thus, resulted in more and more serious and widespread pollution. In view of the increasingly severe environmental conditions, this paper selected decabromodiphenyl ether(Deca-BDE) as the research object, based on the limited research data, taking its flame retardant mechanism as the starting point, and preliminarily discussed how the photodegradation of organic pollutants when Deca-BDE coexisted with other organic pollutants was affected by Deca-BDE. The experimental results show that, when ten Deca-BDE coexist with organic pollutants, the signal strength of organic pollutants photodegradation produce free radicals decreases, the preliminary judgment is Deca-BDE have a shielding effect on free radical signal, or Deca-BDE curbed the photodegradation of organic pollutants, lead to degradation of intermediate reduction, to detect the radical signal intensity weaken. Of course, there are still many areas for improvement and improvement in this study, which need to be proved by further research methods. This study is expected to provide guidance for the scientific classification and treatment of organic pollutants.

Genotoxic Responses of Mitochondrial Oxygen Consumption Rate and Mitochondrial Semiquinone Radicals in Tumor Cells

Our recent report demonstrated that genotoxic stimuli enhance mitochondrial energy metabolism in various tumor cell lines. However, the mitochondrial response against genotoxic stimuli has not been fully elucidated. In this study, to investigate mitochondrial functions in X-irradiated cells, the oxygen consumption rate (OCR) in human cervical adenocarcinoma HeLa cells was examined by electron spin resonance (ESR) spectroscopy with lithium 5,9,14,18,23,27,32,36-octa-n-butoxy-2,3-naphthalocyanine. ESR oximetry demonstrated that basal respiration, ATP-linked respiration, proton leak, maximal respiration, and reserve capacity increased in HeLa cells 24 h after X-irradiation. However, a flow cytometric analysis using MitoTracker Green showed that mitochondrial mass also increased following X-irradiation. When the OCR was standardized to the mitochondria membrane mass, the radiation-induced increases in the respiratory parameters disappeared. This finding indicated that the radiation-induced increase in cellular OCR was explained by an increase in mitochondrial mass but not by the activation of mitochondrial respiratory-related enzymes. In addition, mitochondrial semiquinone radicals at g = 2.004 were detected by low-temperature (110 K) ESR spectroscopy. The ESR signal intensity of semiquinone radicals was enhanced by X-irradiation, suggesting an increase in the electron flow in the electron transport chain. These data will be important to understand the mechanism of radio-sensitization by mitochondria-targeting reagents in tumor cells.

Characterization of lipid oxidation process of beef during repeated freeze-thaw by electron spin resonance technology and Raman spectroscopy

In this study, electron spin resonance (ESR) and Raman spectroscopy were applied to characterize lipid oxidation of beef during repeated freeze–thaw (RFT). Besides the conventional indexes including peroxide values (PV), thiobarbituric acid-reactive substances (TBARS) and acid values (AV) were evaluated, the radical and molecular structure changes were also measured by ESR and Raman spectroscopy. The results showed that PV, TBARS and AV were increased (P<0.05) after RFT. This suggested that lipid oxidation was occurred during RFT. With the increase of radical signal intensity, lower oxidation stability was presented by ESR. Raman intensity of ν(CC) stretching region (1655cm−1) was decreased during RFT. Furthermore, lower Raman intensity ratio of I1655/I1442, I1655/I1745 that determine total unsaturation was also observed. Significant correlations (p<0.01) were obtained among conventional methods, ESR and Raman spectroscopy. Our result has proved that ESR and Raman spectroscopy showed great potential in characterizing lipid oxidation process of beef during RFT.

EPR SPECTROSCOPY STUDIES OF CHANGES IN ERYTHROCYTE MEMBRANES IN PATIENTS WITH LARYNGEAL CANCER

To evaluate microviscosity and sorption capacity of erythrocyte membranes (SCEM) from patients with laryngeal cancer (LC). Samples from 35 patients with LC of stages II and III and 20 healthy volunteers were investigated by electron paramagnetic resonance with Bis(1-oxyl-2,2,6,6-tetramethylpiperidinyl-4)-ester of 5,7-dimethyladamantane-1,3-dicarbonic acid (AdTEMPO) probe. SCEM was evaluated by amount of unabsorbed methylene blue. Microviscosity of erythrocyte membranes was determined by the effective rotational diffusion correlation times (τeff) and a decrease in radical spectrum signal intensity per hour. The most apparent decrease in mobility of the AdTEMPO in erythrocytes was observed prior to washing of erythrocytes with 0.9% NaCl for 5 min after probe insertion. The deceleration after 60 min was observed only in stage II LC. τeff was at control values after washing of erythrocytes of stage II LC 5 min after probe insertion and was significantly reduced in stage III LC in comparison to control. Radical spectrum signal intensity per hour in samples of stage II and III patients prior to and after washing of erythrocytes was on average 1.5-fold higher than that of control. SCEM in samples of stage II and III LC was found in 40 and 33% cases, respectively and was on average significantly reduced in comparison to control. The initial interaction of AdTEMPO with erythrocyte membranes of stage II and III LC patients is accompanied by an increase in τeff, indicating deceleration of probe rotation. τeff of the probe in membranes remains unchanged in 60 min, indicating changes in the structural organization of lipid bilayer and its associated proteins in particular. The similarity of SCEM for both studied groups reflects the pathological changes in function of erythrocyte membranes.

Effects of the components in rice flour on thermal radical generation under microwave irradiation

The relationships between radical generation under microwave irradiation and the components of various types of rice flour were investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to characterize the radicals found in rice flour samples. The EPR spectra revealed that several types of radical (carbon-centered, tyrosyl and semiquinone) were localized in the starch and protein fractions of the rice flour. The signal intensity of the free radicals was observed to increase exponentially with increasing microwave power and residence time. The rice bran samples exhibited the greatest free radical signal intensity, followed by the brown rice samples and the white rice samples. This finding was consistent for both the native and the microwaved samples. The ratio of rice starch to rice protein also played an important role in the generation of radicals.

A novel property of gold nanoparticles: Free radical generation under microwave irradiation.

Gold nanoparticles (GNPs) are known to be effective mediators in microwave hyperthermia. Interaction with an electromagnetic field, large surface to volume ratio, and size quantization of nanoparticles (NPs) can lead to increased cell killing beyond pure heating effects. The purpose of this study is to explore the possibility of free radical generation by GNPs in aqueous media when they are exposed to a microwave field. A number of samples with 500 mM 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in 20 ppm GNP colloidal suspensions were scanned with an electron paramagnetic resonance (EPR)/electron spin resonance spectrometer to generate and detect free radicals. A fixed (9.68 GHz) frequency microwave from the spectrometer has served for both generation and detection of radicals. EPR spectra obtained as first derivatives of intensity with the spectrometer were double integrated to get the free radical signal intensities. Power dependence of radical intensity was studied by applying various levels of microwave power (12.5, 49.7, and 125 mW) while keeping all other scan parameters the same. Free radical signal intensities from initial and final scans, acquired at the same power levels, were compared. Hydroxyl radical (OH⋅) signal was found to be generated due to the exposure of GNP-DMPO colloidal samples to a microwave field. Intensity of OH⋅ signal thus generated at 12.5 mW microwave power for 2.8 min was close to the intensity of OH⋅ signal obtained from a water-DMPO sample exposed to 1.5 Gy ionizing radiation dose. For repeated scans, higher OH⋅ intensities were observed in the final scan for higher power levels applied between the initial and the final scans. Final intensities were higher also for a shorter time interval between the initial and the final scans. Our results observed for the first time demonstrate that GNPs generate OH⋅ radicals in aqueous media when they are exposed to a microwave field. If OH⋅ radicals can be generated close to deoxyribonucleic acid of cells by proper localization of NPs, NP-aided microwave hyperthermia can yield cell killing via both elevated temperature and free radical generation.

Evaluation of absorbed dose in irradiated sugar-containing plant material (peony roots) by an ESR method

Abstract The relationship between electron spin resonance (ESR) signal intensity of irradiated plant materials and sugar content was investigated by spectral analysis using peony roots. A weak background signal near g=2.005 was observed in the roots. After a 10 kGy irradiation, the ESR line broadened and the intensity increased, and the spectral characteristics were similar to a typical spectrum of irradiated food containing crystalline sugars. The free radical concentration was nearly stable 30 days after irradiation. The spectrum of peony root 30 days after irradiation was simulated using the summation of the intensities of six assumed components: radical signals derived from (a) sucrose, (b) glucose, (c) fructose, (d) cellulose, (e) the background signal near g=2.005 and (f) unidentified component. The simulated spectra using the six components were in agreement with the observed sample spectra. The intensity of sucrose radical signal in irradiated samples increased proportionally up to 20 kGy. In addition, the intensity of sucrose radical signals was strongly correlated with the sucrose contents of the samples. The results showed that the radiation sensitivity of sucrose in peony roots was influenced little by other plant constituents. There was also a good correlation between the total area of the spectra and the sucrose content, because the sucrose content was higher than that of other sugars in the samples. In peony roots, estimation of the absorbed dose from the ESR signal intensity may be possible by a calibration method based on the sucrose content.

Mechanism of Gallstones Formation in Women During Menopause (EPR Study)

Abstract The worldwide incidence of gallbladder disease is highly variable. Identification of metabolic alterations like cholesterol metabolism or free radicals may provide insight into the formation of gallstones and provide a basis for prognostic markers. The aim of the study was to identify the pathogenesis and prognostic value of metabolic disorders in gallstone formation in menopausal women. Methods: Menopause-aged women with (group I, 58 patients) and without gallstone disease (group II, 25 patients) were investigated. In each group blood lipid metabolism and blood redox parameters (free Mn2+-ions) and antioxidant system activity (ceruloplasmine/Fe3+-transferrin) were studied using micro enzymatic method and Electron Pramagnetic Resonance (EPR) spectroscopy. Surgically removed gall bladder stones were studied by routine laboratory methods (cholesterol and bilirubin content) and EPR spectroscopy. In model experiments in vitro purified bilirubin was irradiated with visible light in different conditions (in presence and without oxygen). Results: Intensive signal of oxidized bilirubin free radical was detected in the EPR spectra of gallstones. Reduced activity of blood antioxidant ceruloplasmin/F3+-transferrin system and increased content of prooxidants Mn2+-ions were detected in menopausal women blood with gallstone disease. In vitro experiments demonstrated, that prolonged exposure of bilirubin to visible light in the presence of oxygen induces formation of the bilirubin free radicals (EPR signal g= 2.003 AH = 1.0 mT); irradiation of bilirubin in vacuum was not associated with generation of free radicals. Correlation analysis revealed statistically significant correlation between EPR signal intensity of bilirubin free radical in gallstones, activity of ceruloplazmin/F3+-transferrin antioxidant system and content of free Mn 2+ ions in patients' blood (r=-0.5725, p=0.0324; r=0.7805, p=0.0010, respectively). The tight correlation between marker of oxidative stress, Mn 2+ ions EPR signal intensity and HDL-, LDL-cholesterol content in blood (r = 0.910629, p = 0.0324; r = 0.029477, p = 0.0010, respectively) was also revealed. Conclusion: The results of the present study demonstrated the pathophysiological significance of alterations of blood redox-homeostasis during menopause in the gallstone formation. The risk of bilirubin oxidation, which plays a crucial role in the gallstones formation, increases with intensification of oxidative stress. Crystallization of cholesterol in polymeric network of oxidized bilirubin may contribute to gallstone formation.

WE-G-BRE-05: Nanoparticle-Aided Microwave Hyperthermia Is Accompanied By Free Radical Generation and Enhanced Cell Kill

Purpose: Hyperthermia, an established method of cancer treatment used in adjuvant to radiation and chemotherapy, can utilize metallic nanoparticles (NPs) for tumor heating with a microwave electromagnetic field. The high surface-area-to-volume ratio of nanoparticles makes them effective catalysts for free radical generation, thus amplifying the cell-killing effect of hyperthermia. We explore the effect of gold and platinum NPs in generating free radicals in aqueous media under a microwave field. Methods: Spin trap 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was mixed separately with 3.2 nm Mesogold and Mesoplatinum colloidal nanoparticle suspensions in deionized water to trap radicals. The mixtures were injected into a number of glass capillaries and exposed to the 9.68GHz microwave field of an electron paramagnetic resonance (EPR) spectrometer. The microwave radiation from the spectrometer served to both generate and detect the trapped radicals. Each sample was scanned at 12mW microwave power to obtain the initial signal of hydroxyl radicals (OH.), then at 39.8mW followed by 79.8 or 125mW, and finally re-scanned at 12mW. Radical signal intensities obtained by double integration of EPR spectra from the initial and the final scans were then compared. Results: Nanoparticle samples had no intentionally-added free radicals before the initial measurement. While samples with DMPO-water solution showed nomore » OH. signal, all those with AuNPs or PtNPs developed an OH. signal during their first exposure to the microwave field. Depending upon the applied microwave power and time interval between the initial and the final EPR scans, an OH. intensity increase of ∼10-60% was found. This contradicts the typical trend of exponential decay of the OH. signal with time. Conclusion: The consistent increase in OH. intensity establishes that gold and platinum nanoparticles facilitate free radical generation under microwave irradiation. Our results suggest that NP-aided hyperthermia is accompanied by the generation of free radicals, which enhance the cell-killing effects of hyperthermia.« less