ssDNA damage dependence from singlet oxygen concentration at photodynamic interaction

NASA Astrophysics Data System (ADS)

Klimenko, V. V.; Kaydanov, N. E.; Emelyanov, A. K.; Bogdanov, A. A.

2017-11-01

Single stranded DNA damage at photodynamic treatment with Radachlorin photosensitizer was investigated. Chemical trap method was used to evaluate generation of singlet oxygen in water solution. Interaction of singlet oxygen with ssDNA resulted into decrease of the replication activity of ssDNA. DNA stopped replicating during PCR at irradiation doses greater than 15 J/cm2 and concentration of photosensitizer [PS] = 3.8 μM. The dependence of replication activity of ssDNA on generated singlet oxygen concentration was identified.

Generation of hydroxyl radicals and singlet oxygen during oxidation of rhododendrol and rhododendrol-catechol.

PubMed

Miyaji, Akimitsu; Gabe, Yu; Kohno, Masahiro; Baba, Toshihide

2017-03-01

The generation of hydroxyl radicals and singlet oxygen during the oxidation of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol) and 4-(3,4-dihydroxyphenyl)-2-butanol (rhododendrol-catechol) with mushroom tyrosinase in a phosphate buffer (pH 7.4) was examined as the model for the reactive oxygen species generation via the two rhododendrol compounds in melanocytes. The reaction was performed in the presence of 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) spin trap reagents for hydroxyl radical or 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP), an acceptor of singlet oxygen, and their electron spin resonances were measured. An increase in the electron spin resonances signal attributable to the adduct of DMPO reacting with the hydroxyl radical and that of 4-oxo-TEMP reacting with singlet oxygen was observed during the tyrosinase-catalyzed oxidation of rhododendrol and rhododendrol-catechol, indicating the generation of hydroxyl radical and singlet oxygen. Moreover, hydroxyl radical generation was also observed in the autoxidation of rhododendrol-catechol. We show that generation of intermediates during tyrosinase-catalyzed oxidation of rhododendrol enhances oxidative stress in melanocytes.

The influence of excitation radiation parameters on photosensitized generation of singlet oxygen in water

NASA Astrophysics Data System (ADS)

Il'ina, A. D.; Glazov, A. L.; Semenova, I. V.; Vasyutinskii, O. S.

2016-06-01

Photosensitized generation of singlet oxygen with the aid of Radahlorin® photosensitizer has been investigated. The dependences of the intensity of singlet oxygen phosphorescence and photosensitizer fluorescence on the excitation radiation wavelength in the range of 350-440 nm and on the irradiation dose have been obtained. The dependence of the ratio of the sensitizer fluorescence intensity at about 670 nm to the singlet oxygen phosphorescence intensity at a wavelength of 1270 nm on the excitation radiation wavelength is found to be nonmonotonic and have a minimum near the center of the absorption band on its red wing. The results obtained can be used to monitor the singlet oxygen concentration in solutions.

Benzoylation of Ergosterol through Nucleophilic Acyl Substitution and Subsequent Formation of Ergosterol Benzoate Endoperoxide by Reaction with Singlet Oxygen Generated by Photosensitization

ERIC Educational Resources Information Center

Roslaniec, Mary C.; Sanford, Elizabeth M.

2011-01-01

Reactive oxygen species such as singlet oxygen have been a major focus of research in medicine. The effect of singlet oxygen on sterols within biological membranes is becoming increasingly more important. Ergosterol, a vitamin D precursor, is one such sterol. The benzoylation of ergosterol and subsequent reaction with singlet oxygen to form an…

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: An optical boiler generating singlet oxygen O2 (a1Δg)

NASA Astrophysics Data System (ADS)

Lipatov, N. I.; Biryukov, A. S.; Gulyamova, E. S.

2008-12-01

An ecologically perfect generator of singlet oxygen O2 (a1Δg) is proposed which fundamentally differs from existing singlet-oxygen generators. Excited O2 (a1Δg) molecules are generated due to interaction of the O2 (X3Σ-g) molecules with a quasi-monochromatic field, which is supplied from an external source to a closed volume — an optical boiler containing oxygen. It is shown that, by pumping continuously the optical boiler by the light field of power ~3×105 W, it is possible to accumulate up to 40% of singlet oxygen (O2(b1Σ+g)) + (O2 (a1Δg)) in the boiler volume during ~10-2 s.

Fiber-optic Singlet Oxygen [1O2 (1Δg)] Generator Device Serving as a Point Selective Sterilizer

PubMed Central

Aebisher, David; Zamadar, Matibur; Mahendran, Adaickapillai; Ghosh, Goutam; McEntee, Catherine; Greer, Alexander

2016-01-01

Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an “internal” supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fM by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1–4.4 × 107 cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse. PMID:20497367

A Bifunctional Photosensitizer for Enhanced Fractional Photodynamic Therapy: Singlet Oxygen Generation in the Presence and Absence of Light.

PubMed

Turan, Ilke Simsek; Yildiz, Deniz; Turksoy, Abdurrahman; Gunaydin, Gurcan; Akkaya, Engin U

2016-02-18

The photosensitized generation of singlet oxygen within tumor tissues during photodynamic therapy (PDT) is self-limiting, as the already low oxygen concentrations within tumors is further diminished during the process. In certain applications, to minimize photoinduced hypoxia the light is introduced intermittently (fractional PDT) to allow time for the replenishment of cellular oxygen. This condition extends the time required for effective therapy. Herein, we demonstrated that a photosensitizer with an additional 2-pyridone module for trapping singlet oxygen would be useful in fractional PDT. Thus, in the light cycle, the endoperoxide of 2-pyridone is generated along with singlet oxygen. In the dark cycle, the endoperoxide undergoes thermal cycloreversion to produce singlet oxygen, regenerating the 2-pyridone module. As a result, the photodynamic process can continue in the dark as well as in the light cycles. Cell-culture studies validated this working principle in vitro. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exposure of vitamins to UVB and UVA radiation generates singlet oxygen.

PubMed

Knak, Alena; Regensburger, Johannes; Maisch, Tim; Bäumler, Wolfgang

2014-05-01

Deleterious effects of UV radiation in tissue are usually attributed to different mechanisms. Absorption of UVB radiation in cell constituents like DNA causes photochemical reactions. Absorption of UVA radiation in endogenous photosensitizers like vitamins generates singlet oxygen via photosensitized reactions. We investigated two further mechanisms that might be involved in UV mediated cell tissue damage. Firstly, UVB radiation and vitamins also generate singlet oxygen. Secondly, UVB radiation may change the chemical structure of vitamins that may change the role of such endogenous photosensitizers in UVA mediated mechanisms. Vitamins were irradiated in solution using monochromatic UVB (308 nm) or UVA (330, 355, or 370 nm) radiation. Singlet oxygen was directly detected and quantified by its luminescence at 1270 nm. All investigated molecules generated singlet oxygen with a quantum yield ranging from 0.007 (vitamin D3) to 0.64 (nicotinamide) independent of the excitation wavelength. Moreover, pre-irradiation of vitamins with UVB changed their absorption in the UVB and UVA spectral range. Subsequently, molecules such as vitamin E and vitamin K1, which normally exhibit no singlet oxygen generation in the UVA, now produce singlet oxygen when exposed to UVA at 355 nm. This interplay of different UV sources is inevitable when applying serial or parallel irradiation with UVA and UVB in experiments in vitro. These results should be of particular importance for parallel irradiation with UVA and UVB in vivo, e.g. when exposing the skin to solar radiation.

Singlet delta oxygen generation for Chemical Oxygen-Iodine Lasers

NASA Astrophysics Data System (ADS)

Georges, E.; Mouthon, A.; Barraud, R.

1991-10-01

The development of Chemical Oxygen-Iodine Lasers is based on the generation of singlet delta oxygen. To improve the overall efficiency of these lasers, it is necessary to increase the generator production and yield of singlet delta oxygen at low and high pressure, respectively, for subsonic and supersonic lasers. Furthermore, the water vapor content must be as low as possible. A generator model, based on gas-liquid reaction and liquid-vapor equilibrium theories associated with thermophysical evaluations is presented. From model predictions, operating conditions have been drawn to attain the following experimental results in a bubble-column: by increasing the superficial gas velocity, the production of singlet delta oxygen is largely improved at low pressure; by mixing chlorine with an inert gas before injection in the reactor, this yield is maintained constant up to higher pressure. A theoretical analysis of these experimental results and their consequences for both subsonic and supersonic lasers are presented.

Characterization of Photofrin photobleaching for singlet oxygen dose estimation during photodynamic therapy of MLL cells in vitro

NASA Astrophysics Data System (ADS)

Dysart, Jonathan S.; Patterson, Michael S.

2005-06-01

A singlet oxygen dose model is developed for PDT with Photofrin. The model is based on photosensitizer photobleaching kinetics, and incorporates both singlet oxygen and non-singlet oxygen mediated bleaching mechanisms. To test our model, in vitro experiments were performed in which MatLyLu (MLL) cells were incubated in Photofrin and then irradiated with 532 nm light. Photofrin fluorescence was monitored during treatment and, at selected fluence levels, cell viability was determined using a colony formation assay. Cell survival correlated well to calculated singlet oxygen dose, independent of initial Photofrin concentration or oxygenation. About 2 × 108 molecules of singlet oxygen per cell were required to reduce the surviving fraction by 1/e. Analysis of the photobleaching kinetics suggests that the lifetime of singlet oxygen in cells is 0.048 ± 0.005 µs. The generation of fluorescent photoproducts was not a result of singlet oxygen reactions exclusively, and therefore did not yield additional information to aid in quantifying singlet oxygen dose.

Photodynamic therapy: computer modeling of diffusion and reaction phenomena

NASA Astrophysics Data System (ADS)

Hampton, James A.; Mahama, Patricia A.; Fournier, Ronald L.; Henning, Jeffery P.

1996-04-01

We have developed a transient, one-dimensional mathematical model for the reaction and diffusion phenomena that occurs during photodynamic therapy (PDT). This model is referred to as the PDTmodem program. The model is solved by the Crank-Nicholson finite difference technique and can be used to predict the fates of important molecular species within the intercapillary tissue undergoing PDT. The following factors govern molecular oxygen consumption and singlet oxygen generation within a tumor: (1) photosensitizer concentration; (2) fluence rate; and (3) intercapillary spacing. In an effort to maximize direct tumor cell killing, the model allows educated decisions to be made to insure the uniform generation and exposure of singlet oxygen to tumor cells across the intercapillary space. Based on predictions made by the model, we have determined that the singlet oxygen concentration profile within the intercapillary space is controlled by the product of the drug concentration, and light fluence rate. The model predicts that at high levels of this product, within seconds singlet oxygen generation is limited to a small core of cells immediately surrounding the capillary. The remainder of the tumor tissue in the intercapillary space is anoxic and protected from the generation and toxic effects of singlet oxygen. However, at lower values of this product, the PDT-induced anoxic regions are not observed. An important finding is that an optimal value of this product can be defined that maintains the singlet oxygen concentration throughout the intercapillary space at a near constant level. Direct tumor cell killing is therefore postulated to depend on the singlet oxygen exposure, defined as the product of the uniform singlet oxygen concentration and the time of exposure, and not on the total light dose.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Generation of singlet oxygen in fullerene-containing media: 1. Photodesorption of singlet oxygen from fullerene-containing surfaces

NASA Astrophysics Data System (ADS)

Belousova, I. M.; Belousov, V. P.; Danilov, O. B.; Ermakov, A. V.; Kiselev, V. M.; Kislyakov, I. M.; Sosnov, E. N.

2008-03-01

It is shown that upon irradiation of fullerene-containing surfaces by laser or flashlamp pulses, oxygen adsorbed by these surfaces efficiently escapes to the gas phase. The observation of luminescence pulses in the spectral region of 762 and 1268 nm confirms the presence of oxygen molecules in the excited singlet state in the desorbed oxygen. The conditions for optimisation of the efficiency of singlet-oxygen production are studied. It is shown that singlet oxygen at the concentration sufficient for obtaining operation of a fullerene-oxygen-iodine laser can be produced in this way.

X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield.

PubMed

Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C; Goldys, Ewa M

2016-01-28

Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10(8) and (2.0 ± 0.1) × 10(9) singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10(7)-2 × 10(9) singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.

Single Cell Responses to Spatially-Controlled Photosensitized Production of Extracellular Singlet Oxygen

PubMed Central

Pedersen, Brian Wett; Sinks, Louise E.; Breitenbach, Thomas; Schack, Nickolass B.; Vinogradov, Sergei A.; Ogilby, Peter R.

2011-01-01

The response of individual HeLa cells to extracellularly produced singlet oxygen was examined. The spatial domain of singlet oxygen production was controlled using the combination of a membrane-impermeable Pd porphyrin-dendrimer, which served as a photosensitizer, and a focused laser, which served to localize the sensitized production of singlet oxygen. Cells in close proximity to the domain of singlet oxygen production showed morphological changes commonly associated with necrotic cell death. The elapsed post-irradiation “waiting period” before necrosis became apparent depended on (a) the distance between the cell membrane and the domain irradiated, (b) the incident laser fluence and, as such, the initial concentration of singlet oxygen produced, and (c) the lifetime of singlet oxygen. The data imply that singlet oxygen plays a key role in this process of light-induced cell death. The approach of using extracellularly-generated singlet oxygen to induce cell death can provide a solution to a problem that often limits mechanistic studies of intracellularly photosensitized cell death: it can be difficult to quantify the effective light dose, and hence singlet oxygen concentration, when using an intracellular photosensitizer. PMID:21668871

Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries

NASA Astrophysics Data System (ADS)

Mahne, Nika; Schafzahl, Bettina; Leypold, Christian; Leypold, Mario; Grumm, Sandra; Leitgeb, Anita; Strohmeier, Gernot A.; Wilkening, Martin; Fontaine, Olivier; Kramer, Denis; Slugovc, Christian; Borisov, Sergey M.; Freunberger, Stefan A.

2017-03-01

Non-aqueous metal-oxygen batteries depend critically on the reversible formation/decomposition of metal oxides on cycling. Irreversible parasitic reactions cause poor rechargeability, efficiency, and cycle life, and have predominantly been ascribed to the reactivity of reduced oxygen species with cell components. These species, however, cannot fully explain the side reactions. Here we show that singlet oxygen forms at the cathode of a lithium-oxygen cell during discharge and from the onset of charge, and accounts for the majority of parasitic reaction products. The amount increases during discharge, early stages of charge, and charging at higher voltages, and is enhanced by the presence of trace water. Superoxide and peroxide appear to be involved in singlet oxygen generation. Singlet oxygen traps and quenchers can reduce parasitic reactions effectively. Awareness of the highly reactive singlet oxygen in non-aqueous metal-oxygen batteries gives a rationale for future research towards achieving highly reversible cell operation.

Relaxation Process of Photoexcited meso-Naphthylporphyrins while Interacting with DNA and Singlet Oxygen Generation.

PubMed

Hirakawa, Kazutaka; Taguchi, Makoto; Okazaki, Shigetoshi

2015-10-15

Electron donor-connecting cationic porphyrins meso-(1-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (1-NapTMPyP) and meso-(2-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (2-NapTMPyP) were designed and synthesized. DFT calculations speculate that the photoexcited states of 1- and 2-NapTMPyPs can be deactivated via intramolecular electron transfer from the naphthyl moiety to the porphyrin moiety. However, the quenching effect through the intramolecular electron transfer is insufficient, possibly due to the orthogonal position of the electron donor and the porphyrin ring and the relatively small driving force: Gibbs energies are 0.11 and 0.07 eV for 1- and 2-NapTMPyPs, respectively. It was speculated that more than 0.3 eV of the driving force is required to realize effective electron transfer in similar electron-donor connecting porphyrin systems. These porphyrins aggregated around the DNA strand, accelerating the deactivation of their excited singlet state and decreasing their photosensitized singlet oxygen-generating activities. In the presence of a sufficiently large concentration of DNA, these porphyrins can bind to a DNA strand stably, leading to an increased fluorescence quantum yield and lifetime. Singlet oxygen generation was also suppressed by the aggregation of porphyrins around DNA. Although the quantum yield of singlet oxygen generation was recovered in the presence of sufficient DNA, the singlet oxygen generated by DNA-binding porphyrins was significantly smaller than that without DNA. These results suggest that DNA-binding drugs limit the generation of photosensitized singlet oxygen by quenching the DNA strand.

Anthracene-based fluorescent nanoprobes for singlet oxygen detection in biological media.

PubMed

Bresolí-Obach, Roger; Nos, Jaume; Mora, Margarita; Sagristà, Maria Lluïsa; Ruiz-González, Rubén; Nonell, Santi

2016-10-15

We have developed a novel singlet oxygen nanoprobe based on 9,10-anthracenedipropionic acid covalently bound to mesoporous silica nanoparticles. The nanoparticle protects the probe from interactions with proteins, which detract from its ability to detect singlet oxygen. In vitro studies show that the nanoprobe is internalized by cells and is distributed throughout the cytoplasm, thus being capable of detecting intracellularly-generated singlet oxygen. Copyright © 2016 Elsevier Inc. All rights reserved.

The Antitumor Effect of Singlet Oxygen.

PubMed

Bauer, Georg

2016-11-01

Tumor cells are protected against intercellular apoptosis-inducing signaling through expression of membrane-associated catalase and superoxide dismutase. Exogenous singlet oxygen derived from activated photosensitizers or from cold atmospheric plasma causes local inactivation of protective catalase which is followed by the generation of secondary extracellular singlet oxygen. This process is specific for tumor cells and is driven by a complex interaction between H 2 O 2 and peroxynitrite. Secondary singlet oxygen has the potential for autoamplification of its generation, resulting in optimal inactivation of protective catalase and reactivation of intercellular apoptosis-inducing signaling. An increase in the endogenous NO concentration also causes inactivation of catalase and autoamplificatory generation of secondary singlet oxygen. This principle is essential for the antitumor activity of secondary plant products, such as cyanidins and other inhibitors of NO dioxygenase. It seems that the action of the established chemotherapeutic taxol and the recently established antitumor effect of certain azoles are based on the same principles. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Generation of singlet oxygen in fullerene-containing media: 2. Fullerene-containing solutions

NASA Astrophysics Data System (ADS)

Bagrov, I. V.; Belousova, I. M.; Grenishin, A. S.; Danilov, O. B.; Ermakov, A. V.; Kiselev, V. M.; Kislyakov, I. M.; Murav'eva, T. D.; Sosnov, E. N.

2008-03-01

The generation of singlet oxygen in fullerene solutions is studied by luminescence methods upon excitation by pulsed, repetitively pulsed, and continuous radiation sources. The concentration of singlet oxygen in solutions is measured in stationary and pulsed irradiation regimes. The rate constants of quenching of O2(1Δg) by fullerenes C70 and C60 in the CCl4 solution are measured to be (7.2±0.1)×107 L mol-1 s-1 and less than 6×104 L mol-1 s-1, respectively. The temperature and photolytic variations in the generation properties of the fullerene solution exposed to intense continuous radiation are studied by the methods of optical and EPR spectroscopy. Pulsed irradiation resulted in the production of singlet oxygen in suspensions of fullerene-like structures, in particular, astralenes. A liquid pulsed singlet-oxygen generator based on the fullerene solution in CCl4 is developed and studied, in which the yield of O2 (1Δg) to the gas phase at concentrations up to 5×1016 cm-3 is obtained.

Singlet oxygen generation during the oxidation of L-tyrosine and L-dopa with mushroom tyrosinase.

PubMed

Miyaji, Akimitsu; Kohno, Masahiro; Inoue, Yoshihiro; Baba, Toshihide

2016-03-18

The generation of singlet oxygen during the oxidation of tyrosine and L-dopa using mushroom tyrosinase in a phosphate buffer (pH 7.4), the model of melanin synthesis in melanocytes, was examined. The reaction was performed in the presence of 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP), an acceptor of singlet oxygen and the electron spin resonance (ESR) of the spin adduct, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (4-oxo-TEMPO), was measured. An increase in the ESR signal attributable to 4-oxo-TEMPO was observed during the oxidation of tyrosine and L-dopa with tyrosinase, indicating the generation of singlet oxygen. The results suggest that (1)O2 generation via tyrosinase-catalyzed melanin synthesis occurs in melanocyte. Copyright © 2016 Elsevier Inc. All rights reserved.

The Contribution of Singlet Oxygen to Insulin Resistance

PubMed Central

2017-01-01

Insulin resistance contributes to the development of diabetes and cardiovascular dysfunctions. Recent studies showed that elevated singlet oxygen-mediated lipid peroxidation precedes and predicts diet-induced insulin resistance (IR), and neutrophils were suggested to be responsible for such singlet oxygen production. This review highlights literature suggesting that insulin-responsive cells such as endothelial cells, hepatocytes, adipocytes, and myocytes also produce singlet oxygen, which contributes to insulin resistance, for example, by generating bioactive aldehydes, inducing endoplasmic reticulum (ER) stress, and modifying mitochondrial DNA. In these cells, nutrient overload leads to the activation of Toll-like receptor 4 and other receptors, leading to the production of both peroxynitrite and hydrogen peroxide, which react to produce singlet oxygen. Cytochrome P450 2E1 and cytochrome c also contribute to singlet oxygen formation in the ER and mitochondria, respectively. Endothelial cell-derived singlet oxygen is suggested to mediate the formation of oxidized low-density lipoprotein which perpetuates IR, partly through neutrophil recruitment to adipose tissue. New singlet oxygen-involving pathways for the formation of IR-inducing bioactive aldehydes such as 4-hydroperoxy-(or hydroxy or oxo)-2-nonenal, malondialdehyde, and cholesterol secosterol A are proposed. Strategies against IR should target the singlet oxygen-producing pathways, singlet oxygen quenching, and singlet oxygen-induced cellular responses. PMID:29081894

The Contribution of Singlet Oxygen to Insulin Resistance.

PubMed

Onyango, Arnold N

2017-01-01

Insulin resistance contributes to the development of diabetes and cardiovascular dysfunctions. Recent studies showed that elevated singlet oxygen-mediated lipid peroxidation precedes and predicts diet-induced insulin resistance (IR), and neutrophils were suggested to be responsible for such singlet oxygen production. This review highlights literature suggesting that insulin-responsive cells such as endothelial cells, hepatocytes, adipocytes, and myocytes also produce singlet oxygen, which contributes to insulin resistance, for example, by generating bioactive aldehydes, inducing endoplasmic reticulum (ER) stress, and modifying mitochondrial DNA. In these cells, nutrient overload leads to the activation of Toll-like receptor 4 and other receptors, leading to the production of both peroxynitrite and hydrogen peroxide, which react to produce singlet oxygen. Cytochrome P450 2E1 and cytochrome c also contribute to singlet oxygen formation in the ER and mitochondria, respectively. Endothelial cell-derived singlet oxygen is suggested to mediate the formation of oxidized low-density lipoprotein which perpetuates IR, partly through neutrophil recruitment to adipose tissue. New singlet oxygen-involving pathways for the formation of IR-inducing bioactive aldehydes such as 4-hydroperoxy-(or hydroxy or oxo)-2-nonenal, malondialdehyde, and cholesterol secosterol A are proposed. Strategies against IR should target the singlet oxygen-producing pathways, singlet oxygen quenching, and singlet oxygen-induced cellular responses.

Time-resolved singlet oxygen luminescence detection under photodynamic therapy relevant conditions: comparison of ex vivo application of two photosensitizer formulations

NASA Astrophysics Data System (ADS)

Schlothauer, Jan C.; Hackbarth, Steffen; Jäger, Lutz; Drobniewski, Kai; Patel, Hemantbhai; Gorun, Sergiu M.; Röder, Beate

2012-11-01

Singlet oxygen plays a crucial role in photo-dermatology and photodynamic therapy (PDT) of cancer. Its direct observation by measuring the phosphorescence at 1270 nm, however, is still challenging due to the very low emission probability. It is especially challenging for the time-resolved detection of singlet oxygen kinetics in vivo which is of special interest for biomedical applications. Photosensitized generation of singlet oxygen, in pig ear skin as model for human skin, is investigated here. Two photosensitizers (PS) were topically applied to the pig ear skin and examined in a comparative study, which include the amphiphilic pheophorbide-a and the highly hydrophobic perfluoroalkylated zinc phthalocyanine (F64PcZn). Fluorescence microscopy indicates the exclusive accumulation of pheophorbide-a in the stratum corneum, while F64PcZn can also accumulate in deeper layers of the epidermis of the pig ear skin. The kinetics obtained with phosphorescence measurements show the singlet oxygen interaction with the PS microenvironment. Different generation sites of singlet oxygen correlate with the luminescence kinetics. The results show that singlet oxygen luminescence detection can be used as a diagnostic tool, not only for research, but also during treatment. The detection methodology is suitable for the monitoring of chemical quenchers' oxidation as well as O2 saturation at singlet oxygen concentration levels relevant to PDT treatment protocols.

Singlet Delta oxygen generation for chemical oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Georges, E.; Mouthon, A.; Barraud, R.

To improve the overall efficiency of chemical oxygen-iodine lasers, it is necessary to increase the generator production and yield of singlet delta oxygen at low and high pressure, respectively, for subsonic and supersonic lasers. The water vapor content must also be as low as possible. A generator model based on gas-liquid reaction and liquid-vapor equilibrium theories is presented. From model predictions, operating conditions have been drawn to attain the following experimental results in a bubble-column: by increasing the superficial gas velocity, the production of singlet delta oxygen is largely improved at low pressure; by mixing chlorine with an inert gas before injection in the reactor, this yield is maintained constant up to higher pressure.

Laser-induced generation of singlet oxygen and its role in the cerebrovascular physiology

NASA Astrophysics Data System (ADS)

Semyachkina-Glushkovskaya, O. V.; Sokolovski, S. G.; Goltsov, A.; Gekaluyk, A. S.; Saranceva, E. I.; Bragina, O. A.; Tuchin, V. V.; Rafailov, E. U.

2017-09-01

For over 55 years, laser technology has expanded from laboratory research to widespread fields, for example telecommunication and data storage amongst others. Recently application of lasers in biology and medicine presents itself as one of the emerging areas. In this review, we will outline the recent advances in using lasers for the generation of singlet oxygen, traditionally used to kill tumour cells or induce thrombotic stroke model due to damage vascular effects. Over the last two decade, completely new results on cerebrovascular effects of singlet oxygen generated during photodynamic therapy (PDT) have been shown alongside promising applications for delivery of drugs and nanoparticles into the brain for therapy of brain cancer. Furthermore, a ;gold key; has been found to overcome the limitations of PDT, such as low light penetration and high toxicity of photosensitizers, by direct generation of singlet oxygen using quantum-dot laser diodes emitting in the near infrared (NIR) spectral range. It is our motivation to highlight these pioneering results in this review, to improve understanding of the biological role of singlet oxygen and to provide new perspectives for improving clinical application of laser based therapy in further research.

Graphene oxide functionalized with methylene blue and its performance in singlet oxygen generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojtoniszak, M., E-mail: mwojtoniszak@zut.edu.pl; Rogińska, D.; Machaliński, B.

2013-07-15

Graphical abstract: - Highlights: • Adsorption of methylene blue (MB) on graphene oxide (GO). • Characterization of graphene oxide–methylene blue nanocomposite (MB–GO). • Examination of MB–GO efficiency in singlet oxygen generation (SOG). • MB–GO performs higher SOG efficiency than pristine MB. - Abstract: Due to unique electronic, mechanical, optical and structural properties, graphene has shown promising applications in many fields, including biomedicine. One of them is noninvasive anticancer therapy – photodynamic therapy (PDT), where singlet oxygen (SO), generated under the irradiation of light with appropriate wavelengths, kills cancer cells. In this study, authors report graphene oxide (GO) noncovalent functionalization withmore » methylene blue (MB). MB molecules underwent adsorption on the surface of GO. Detailed characterization of the obtained material was carried out with UV–vis spectroscopy, Raman spectroscopy, FT-IR spectroscopy, and confocal laser scanning microscopy. Furthermore, its performance in singlet oxygen generation (SOG) under irradiation of laser with excitation wavelengths of 785 nm was investigated. Interestingly, GO functionalized with MB (MB–GO) showed enhanced efficiency in singlet oxygen generation compared to pristine MB. The efficiency in SOG was detected by photobleaching of 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABMDMA). These results indicate the material is promising in PDT anticancer therapy and further in vitro and in vivo studies are required.« less

Combined phosphorescence-holographic approach for singlet oxygen detection in biological media

NASA Astrophysics Data System (ADS)

Semenova, I. V.; Belashov, A. V.; Beltukova, D. M.; Petrov, N. V.; Vasyutinskii, O. S.

2015-06-01

The paper presents a novel combined approach aimed to detect and monitor singlet oxygen molecules in biological specimens by means of the simultaneous recording and monitoring of their deactivation dynamics in the two complementary channels: radiative and nonradiative. The approach involves both the direct registration of phosphorescence at the wavelength of about 1270 nm caused by radiative relaxation of excited singlet oxygen molecules and holographic recording of thermal disturbances in the medium produced by their nonradiative relaxation. The data provides a complete set of information on singlet oxygen location and dynamics in the medium. The approach was validated in the case study of photosensitized generation of singlet oxygen in onion cell structures.

Singlet oxygen production in Chlamydomonas reinhardtii under heat stress.

PubMed

Prasad, Ankush; Ferretti, Ursula; Sedlářová, Michaela; Pospíšil, Pavel

2016-02-01

In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase.

Molecular demultiplexer as a terminator automaton.

PubMed

Turan, Ilke S; Gunaydin, Gurcan; Ayan, Seylan; Akkaya, Engin U

2018-02-23

Molecular logic gates are expected to play an important role on the way to information processing therapeutic agents, especially considering the wide variety of physical and chemical responses that they can elicit in response to the inputs applied. Here, we show that a 1:2 demultiplexer based on a Zn 2+ -terpyridine-Bodipy conjugate with a quenched fluorescent emission, is efficient in photosensitized singlet oxygen generation as inferred from trap compound experiments and cell culture data. However, once the singlet oxygen generated by photosensitization triggers apoptotic response, the Zn 2+ complex then interacts with the exposed phosphatidylserine lipids in the external leaflet of the membrane bilayer, autonomously switching off singlet oxygen generation, and simultaneously switching on a bright emission response. This is the confirmatory signal of the cancer cell death by the action of molecular automaton and the confinement of unintended damage by excessive singlet oxygen production.

Singlet oxygen generator for a solar powered chemically pumped iodine laser

NASA Technical Reports Server (NTRS)

Busch, G. E.

1984-01-01

The potential of solid phase endoperoxides as a means to produce single-delta oxygen in the gas phase in concentrations useful to chemical oxygen-iodine lasers was investigated. The 1,4 - endoperoxide of ethyl 3- (4-methyl - 1-naphthyl) propanoate was deposited over an indium-oxide layer on a glass plate. Single-delta oxygen was released from the endoperoxide upon heating the organic film by means of an electrical discharge through the conductive indium oxide coating. The evolution of singlet-delta oxygen was determined by measuring the dimol emission signal at 634 nm. Comparison of the measured signal with an analytic model leads to two main conclusions: virtually all the oxygen being evolved is in the singlet-delta state and in the gas phase, and there is no significant quenching other than energy pooling on the time scale of the experiment (approximately 10 msec). The use of solid phase endoperoxide as a singlet-delta oxygen generator for an oxygen-iodine laser appears promising.

Trojan Horse for Light-Triggered Bifurcated Production of Singlet Oxygen and Fenton-Reactive Iron within Cancer Cells.

PubMed

Cioloboc, Daniela; Kennedy, Christopher; Boice, Emily N; Clark, Emily R; Kurtz, Donald M

2018-01-08

Traditional photodynamic therapy for cancer relies on dye-photosensitized generation of singlet oxygen. However, therapeutically effective singlet oxygen generation requires well-oxygenated tissues, whereas many tumor environments tend to be hypoxic. We describe a platform for targeted enhancement of photodynamic therapy that produces singlet oxygen in oxygenated environments and hydroxyl radical, which is typically regarded as the most toxic reactive oxygen species, in hypoxic environments. The 24-subunit iron storage protein bacterioferritin (Bfr) has the unique property of binding 12 heme groups in its protein shell. We inserted the isostructural photosensitizer, zinc(II) protoporphyrin IX (ZnP), in place of the hemes and extended the surface-exposed N-terminal ends of the Bfr subunits with a peptide targeting a receptor that is hyperexpressed on the cell surface of many tumors and tumor vasculature. We then loaded the inner cavity with ∼2500 irons as a ferric oxyhydroxide polymer and finally conjugated 2 kDa polyethylene glycol to the outer surface. We showed that the inserted ZnP photosensitizes generation of both singlet oxygen and the hydroxyl radical, the latter via the reaction of photoreleased ferrous iron with hydrogen peroxide. This targeted iron-loaded ZnP-Bfr construct was endocytosed by C32 melanoma cells and localized to lysosomes. Irradiating the treated cells with light at wavelengths overlapping the ZnP Soret absorption band induced photosensitized intracellular Fe 2+ release and substantial lowering of cell viability. This targeted, light-triggered production of intracellular singlet oxygen and Fenton-reactive iron could potentially be developed into a phototherapeutic adjunct for many types of cancers.

Photosensitized generation of singlet oxygen by rhenium(I) complex

NASA Astrophysics Data System (ADS)

Burchinov, A. N.; Kiselev, V. M.; Penni, A. A.; Khistyaeva, V. V.

2015-12-01

The photosensitized generation of singlet oxygen in solutions of rhenium(I) complex fac-[Re(bipy)(CO)3NCCH3]+OTf-, where bipy=2,2'-bipyridine, in chloride methylene and carbon tetrachloride under continuous LED irradiation in the UV and visible ranges has been investigated.

Remote-Controlled Release of Singlet Oxygen by the Plasmonic Heating of Endoperoxide-Modified Gold Nanorods: Towards a Paradigm Change in Photodynamic Therapy.

PubMed

Kolemen, Safacan; Ozdemir, Tugba; Lee, Dayoung; Kim, Gyoung Mi; Karatas, Tugce; Yoon, Juyoung; Akkaya, Engin U

2016-03-07

The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self-limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Singlet oxygen generator for a supersonic chemical oxygen iodine laser: parametric study and recovery of chemicals

NASA Astrophysics Data System (ADS)

Spalek, Otomar; Kodymova, Jarmila

1997-04-01

A jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was studied including singlet delta oxygen, O2(1(Delta) g), and residual chlorine concentration measurements. The investigation was intended mainly for a water vapor measurement in gas effluent of generator in dependence on properties of liquid jets: a chemical composition and temperature of the input liquid (alkaline solution of hydrogen peroxide), a liquid jets diameter and their geometrical arrangement. Effects of these parameters on output power of a small-scale supersonic laser were studied as well. Possible approaches to a chemical fuels management in a chemical oxygen-iodine laser for industrial applications are considered. An 'open loop' cycle with a possible use of sodium hydroxide, and a 'closed loop' cycle with a regeneration of both potassium hydroxide and hydrogen peroxide are discussed.

Performance Characteristics of Jet-type Generator of Singlet Oxygen for Supersonic Chemical Oxygen-Iodine Laser*1

NASA Astrophysics Data System (ADS)

Kodymová, Jarmila; Špalek, Otomar

1998-01-01

A jet-type singlet oxygen generator based on a gas-liquid chemical reaction yielding singlet oxygen, O2(1Δ g), for pumping the supersonic chemical oxygen-iodine laser was investigated. In addition to O2(1Δ g) and residual chlorine concentrations, a content of water formed during O2(1Δ g) generation was estimated (because of its detrimental effect on lasing) in gas flowing from the generator to the laser active region. The experimental conditions were determined under which an effect of liquid droplets escaping from the generator was negligible, and accordingly, a content of water vapour was suppressed to a value corresponding to the saturated water vapour pressure. It was also proved that a reduction in the relative water content, and a consequent increase in the laser output power, could be achieved by increasing peroxide and hydroxide concentration in the generator liquid, and by decreasing a liquid temperature and a total pressure in the generator.

Highly efficient oxidation of amines to imines by singlet oxygen and its application in Ugi-type reactions.

PubMed

Jiang, Gaoxi; Chen, Jian; Huang, Jie-Sheng; Che, Chi-Ming

2009-10-15

A variety of secondary benzylic amines were oxidized to imines in 90% to >99% yields by singlet oxygen generated from oxygen and a porphyrin photosensitizer. On the basis of these reactions, a protocol was developed for oxidative Ugi-type reactions with singlet oxygen as the oxidant. This protocol has been used to synthesize C1- and N-functionalized benzylic amines in up to 96% yields.

Evidence that Singlet Oxygen-induced Human T Helper Cell Apoptosis Is the Basic Mechanism of Ultraviolet-A Radiation Phototherapy

PubMed Central

Morita, Akimichi; Werfel, Thomas; Stege, Helger; Ahrens, Constanze; Karmann, Karin; Grewe, Markus; Grether-Beck, Susanne; Ruzicka, Thomas; Kapp, Alexander; Klotz, Lars-Oliver; Sies, Helmut; Krutmann, Jean

1997-01-01

Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and other T cell mediated, inflammatory skin diseases. In the present study, successful phototherapy of atopic dermatitis was found to result from UVA radiation-induced apoptosis in skin-infiltrating T helper cells, leading to T cell depletion from eczematous skin. In vitro, UVA radiation-induced human T helper cell apoptosis was mediated through the FAS/FAS-ligand system, which was activated in irradiated T cells as a consequence of singlet oxygen generation. These studies demonstrate that singlet oxygen is a potent trigger for the induction of human T cell apoptosis. They also identify singlet oxygen generation as a fundamental mechanism of action operative in phototherapy. PMID:9362536

Cellular defense against singlet oxygen-induced oxidative damage by cytosolic NADP+-dependent isocitrate dehydrogenase.

PubMed

Kim, Sun Yee; Park, Jeen-Woo

2003-03-01

Singlet oxygen (1O2) is a highly reactive form of molecular oxygen that may harm living systems by oxidizing critical cellular macromolecules. Recently, we have shown that NADP+-dependent isocitrate dehydrogenase is involved in the supply of NADPH needed for GSH production against cellular oxidative damage. In this study, we investigated the role of cytosolic form of NADP+-dependent isocitrate dehydrogenase (IDPc) against singlet oxygen-induced cytotoxicity by comparing the relative degree of cellular responses in three different NIH3T3 cells with stable transfection with the cDNA for mouse IDPc in sense and antisense orientations, where IDPc activities were 2.3-fold higher and 39% lower, respectively, than that in the parental cells carrying the vector alone. Upon exposure to singlet oxygen generated from photoactivated dye, the cells with low levels of IDPc became more sensitive to cell killing. Lipid peroxidation, protein oxidation, oxidative DNA damage and intracellular peroxide generation were higher in the cell-line expressing the lower level of IDPc. However, the cells with the highly over-expressed IDPc exhibited enhanced resistance against singlet oxygen, compared to the control cells. The data indicate that IDPc plays an important role in cellular defense against singlet oxygen-induced oxidative injury.

Generation of singlet oxygen in fullerene-containing media: 2. Fullerene-containing solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagrov, I V; Belousova, I M; Grenishin, A S

2008-03-31

The generation of singlet oxygen in fullerene solutions is studied by luminescence methods upon excitation by pulsed, repetitively pulsed, and continuous radiation sources. The concentration of singlet oxygen in solutions is measured in stationary and pulsed irradiation regimes. The rate constants of quenching of O{sub 2}({sup 1}{delta}{sub g}) by fullerenes C{sub 70} and C{sub 60} in the CCl{sub 4} solution are measured to be (7.2{+-}0.1)x10{sup 7} L mol{sup -1} s{sup -1} and less than 6x10{sup 4} L mol{sup -1} s{sup -1}, respectively. The temperature and photolytic variations in the generation properties of the fullerene solution exposed to intense continuous radiationmore » are studied by the methods of optical and EPR spectroscopy. Pulsed irradiation resulted in the production of singlet oxygen in suspensions of fullerene-like structures, in particular, astralenes. A liquid pulsed singlet-oxygen generator based on the fullerene solution in CCl{sub 4} is developed and studied, in which the yield of O{sub 2} ({sup 1}{delta}{sub g}) to the gas phase at concentrations up to 5x10{sup 16} cm{sup -3} is obtained. (laser applications and other topics in quantum electronics)« less

Mechanism of singlet oxygen deactivation in an electric discharge oxygen – iodine laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azyazov, V N; Mikheyev, P A; Torbin, A P

2014-12-31

We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O{sub 2}(a {sup 1}Δ) + O{sub 3}(ν) → 2O{sub 2} + O on the removal rate of O{sub 2}(a {sup 1}Δ) in an electric-discharge-driven oxygen – iodine laser. This reaction has been shown to be a major channel of O{sub 2}(a {sup 1}Δ) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O{sub 2}(a {sup 1}Δ) in the discharge region of the generator. (lasers)

Photoactivatable protein labeling by singlet oxygen mediated reactions.

PubMed

To, Tsz-Leung; Medzihradszky, Katalin F; Burlingame, Alma L; DeGrado, William F; Jo, Hyunil; Shu, Xiaokun

2016-07-15

Protein-protein interactions regulate many biological processes. Identification of interacting proteins is thus an important step toward molecular understanding of cell signaling. The aim of this study was to investigate the use of photo-generated singlet oxygen and a small molecule for proximity labeling of interacting proteins in cellular environment. The protein of interest (POI) was fused with a small singlet oxygen photosensitizer (miniSOG), which generates singlet oxygen ((1)O2) upon irradiation. The locally generated singlet oxygen then activated a biotin-conjugated thiol molecule to form a covalent bond with the proteins nearby. The labeled proteins can then be separated and subsequently identified by mass spectrometry. To demonstrate the applicability of this labeling technology, we fused the miniSOG to Skp2, an F-box protein of the SCF ubiquitin ligase, and expressed the fusion protein in mammalian cells and identified that the surface cysteine of its interacting partner Skp1 was labeled by the biotin-thiol molecule. This photoactivatable protein labeling method may find important applications including identification of weak and transient protein-protein interactions in the native cellular context, as well as spatial and temporal control of protein labeling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solid-phase fullerene-like nanostructures as singlet oxygen photosensitizers in liquid media

NASA Astrophysics Data System (ADS)

Belousova, I. M.; Danilov, O. B.; Kiselev, V. M.; Kislyakov, I. M.; Kris'ko, T. K.; Murav'eva, T. D.; Videnichev, D. A.

2007-04-01

Singlet oxygen generation by fullerene and astralen containing surfaces and powders under visible irradiation was studied in water and organic liquids by means of 1Δ g state luminescence and chemical scavenger transmittance measurements. The chemical method, pioneered for solid photosensitizers of 10 II, allowed to measure the singlet oxygen concentration in the aqueous medium down to 10 8 cm -3. The singlet oxygen sensitizing by the solid-phase fullerene-containing systems was found to be 100 times less effective then by fullerene in solution. The results obtained confirm the applicability of these structures in biology and medicine.

Reevaluation of analytical methods for photogenerated singlet oxygen

PubMed Central

Nakamura, Keisuke; Ishiyama, Kirika; Ikai, Hiroyo; Kanno, Taro; Sasaki, Keiichi; Niwano, Yoshimi; Kohno, Masahiro

2011-01-01

The aim of the present study is to compare different analytical methods for singlet oxygen and to discuss an appropriate way to evaluate the yield of singlet oxygen photogenerated from photosensitizers. Singlet oxygen photogenerated from rose bengal was evaluated by electron spin resonance analysis using sterically hindered amines, spectrophotometric analysis of 1,3-diphenylisobenzofuran oxidation, and analysis of fluorescent probe (Singlet Oxygen Sensor Green®). All of the analytical methods could evaluate the relative yield of singlet oxygen. The sensitivity of the analytical methods was 1,3-diphenylisobenzofuran < electron spin resonance < Singlet Oxygen Sensor Green®. However, Singlet Oxygen Sensor Green® could be used only when the concentration of rose bengal was very low (<1 µM). In addition, since the absorption spectra of 1,3-diphenylisobenzofuran is considerably changed by irradiation of 405 nm laser, photosensitizers which are excited by light with a wavelength of around 400 nm such as hematoporphyrin cannot be used in the 1,3-diphenylisobenzofuran oxidation method. On the other hand, electron spin resonance analysis using a sterically hindered amine, especially 2,2,6,6-tetramethyl-4-piperidinol and 2,2,5,5-tetramethyl-3-pyrroline-3-carboxamide, had proper sensitivity and wide detectable range for the yield of photogenerated singlet oxygen. Therefore, in photodynamic therapy, it is suggested that the relative yield of singlet oxygen generated by various photosensitizers can be evaluated properly by electron spin resonance analysis. PMID:21980223

Singlet oxygen generation in gas discharge for oxygen-iodine laser pumping

NASA Astrophysics Data System (ADS)

Lopaev, D. V.; Braginsky, O. V.; Klopovsky, K. S.; Kovalev, A. S.; Mankelevich, Yu. A.; Popov, N. A.; Rakhimov, A. T.; Rakhimova, T. V.; Vasilieva, A. N.

2004-09-01

The possibility of development of effective discharged singlet oxygen (SO) generator (DSOG) for oxygen-iodine laser (OIL) is studied in detail. Researches of kinetics of oxygen atoms and oxygen molecules in the lowest metastable singlet states have been carried out in the different discharges and its afterglow (DC discharges, E-beam controlled discharge and RF discharges) in both CW and pulsed mode in a wide range of conditions (pressures, gas mixtures, energy deposits etc.). The models developed for all the discharges have allowed us to analyze SO generation and loss mechanisms and to find out the key-parameters controlling the highest SO yield. It is shown that in addition to spatial plasma uniformity at low E/N and high specific energy deposit per oxygen molecule, DSOG must be oxygen atom free to avoid fast three-body quenching of SO by atomic oxygen with increasing pressure and thereby to provide pressure scaling (in tens Torrs) for applying to real OIL systems.

Evaluation of phototoxicity of dendritic porphyrin-based phosphorescent oxygen probes: an in vitro study†

PubMed Central

Lebedev, Artem Y.; Marchi, Enrico; Yuan, Min; Esipova, Tatiana V.; Bergamini, Giacomo; Wilson, David F.

2013-01-01

Biological oxygen measurements by phosphorescence quenching make use of exogenous phosphorescent probes, which are introduced directly into the medium of interest (e.g. blood or interstitial fluid) where they serve as molecular sensors for oxygen. The byproduct of the quenching reaction is singlet oxygen, a highly reactive species capable of damaging biological tissue. Consequently, potential probe phototoxicity is a concern for biological applications. Herein, we compared the ability of polyethyleneglycol (PEG)-coated Pd tetrabenzoporphyrin (PdTBP)-based dendritic nanoprobes of three successive generations to sensitize singlet oxygen. It was found that the size of the dendrimer has practically no effect on the singlet oxygen sensitization efficiency in spite of the strong attenuation of the triplet quenching rate with an increase in the dendrimer generation. This unexpected result is due to the fact that the lifetime of the PdTBP triplet state in the absence of oxygen increases with dendritic generation, thus compensating for the concomitant decrease in the rate of quenching. Nevertheless, in spite of their ability to sensitize singlet oxygen, the phosphorescent probes were found to be non-phototoxic when compared with the commonly used photodynamic drug Photofrin in a standard cell-survival assay. The lack of phototoxicity is presumably due to the inability of PEGylated probes to associate with cell surfaces and/or penetrate cellular membranes. In contrast, conventional photosensitizers bind to cell components and act by generating singlet oxygen inside or in the immediate vicinity of cellular organelles. Therefore, PEGylated dendritic probes are safe to use for tissue oxygen measurements as long as the light doses are less than or equal to those commonly employed in photodynamic therapy. PMID:21409208

Photoinduced Electron Transfer-based Halogen-free Photosensitizers: Covalent meso-Aryl (Phenyl, Naphthyl, Anthryl, and Pyrenyl) as Electron Donors to Effectively Induce the Formation of the Excited Triplet State and Singlet Oxygen for BODIPY Compounds.

PubMed

Zhang, Xian-Fu; Feng, Nan

2017-09-19

Pristine BODIPY compounds have negligible efficiency to generate the excited triplet state and singlet oxygen. In this report, we show that attaching a good electron donor to the BODIPY core can lead to singlet oxygen formation with up to 58 % quantum efficiency. For this purpose, BODIPYs with meso-aryl groups (phenyl, naphthyl, anthryl, and pyrenyl) were synthesized and characterized. The fluorescence, excited triplet state, and singlet oxygen formation properties for these compounds were measured in various solvents by UV/Vis absorption, steady-state and time-resolved fluorescence methods, as well as laser flash photolysis technique. In particular, the presence of anthryl and pyrenyl showed substantial enhancement on the singlet oxygen formation ability of BODIPY with up to 58 % and 34 % quantum efficiency, respectively, owing to their stronger electron-donating ability. Upon the increase in singlet oxygen formation, the fluorescence quantum yield and lifetime values of the aryl-BODIPY showed a concomitant decrease. The increase in solvent polarity enhances the singlet oxygen generation but decreases the fluorescence quantum yield. The results are explained by the presence of intramolecular photoinduced electron transfer from the aryl moiety to BODIPY core. This method of promoting T 1 formation is very different from the traditional heavy atom effect by I, Br, or transition metal atoms. This type of novel photosensitizers may find important applications in organic oxygenation reactions and photodynamic therapy of tumors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

BODIPY-Au(I): A Photosensitizer for Singlet Oxygen Generation and Photodynamic Therapy.

PubMed

Üçüncü, Muhammed; Karakuş, Erman; Kurulgan Demirci, Eylem; Sayar, Melike; Dartar, Suay; Emrullahoğlu, Mustafa

2017-05-19

Upon complexation with Au(I), a photoinactive BODIPY derivative was transformed into a highly photoactive triplet sensitizer. Along with high efficiency in singlet oxygen generation (Φ Δ = 0.84), the new BODIPY-Au(I) skeleton showed excellent photocytotoxic activity against cancer cell lines (EC 50 = 2.5 nM).

Novel fully-BODIPY functionalized cyclotetraphosphazene photosensitizers having high singlet oxygen quantum yields

NASA Astrophysics Data System (ADS)

Şenkuytu, Elif; Eçik, Esra Tanrıverdi

2017-07-01

Novel fully-BODIPY functionalized dendrimeric cyclotetraphosphazenes (FBCP 1 and 2) have been synthesized and characterized by 1H, 13C and 31P NMR spectroscopies. The photophysical and photochemical properties of FBCP 1 and 2 are investigated in dichloromethane solution. The effectiveness of singlet oxygen generation was measured for FBCP 1 and 2 by UV-Vis spectra monitoring of the solution of 1,3-diphenylisobenzofuran (DPBF), which is a well-known trapping molecule used in detection of singlet oxygen. FBCP 1 and 2 show high molar extinction coefficients in the NIR region, good singlet oxygen quantum yields and appropriate photo degradation. The data presented in the work indicate that the dendrimeric cyclotetraphosphazenes are effective singlet oxygen photosensitizers that might be used for various areas of applications such as photodynamic therapy and photocatalysis.

Aerobic photoreactivity of synthetic eumelanins and pheomelanins: generation of singlet oxygen and superoxide anion.

PubMed

Szewczyk, Grzegorz; Zadlo, Andrzej; Sarna, Michal; Ito, Shosuke; Wakamatsu, Kazumasa; Sarna, Tadeusz

2016-11-01

In this work, we examined photoreactivity of synthetic eumelanins, formed by autooxidation of DOPA, or enzymatic oxidation of 5,6-dihydroxyindole-2-carboxylic acid and synthetic pheomelanins obtained by enzymatic oxidation of 5-S-cysteinyldopa or 1:1 mixture of DOPA and cysteine. Electron paramagnetic resonance oximetry and spin trapping were used to measure oxygen consumption and formation of superoxide anion induced by irradiation of melanin with blue light, and time-resolved near-infrared luminescence was employed to determine the photoformation of singlet oxygen between 300 and 600 nm. Both superoxide anion and singlet oxygen were photogenerated by the synthetic melanins albeit with different efficiency. At 450-nm, quantum yield of singlet oxygen was very low (~10 -4 ) but it strongly increased in the UV region. The melanins quenched singlet oxygen efficiently, indicating that photogeneration and quenching of singlet oxygen may play an important role in aerobic photochemistry of melanin pigments and could contribute to their photodegradation and photoaging. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Oxygen-iodine ejector laser with a centrifugal bubbling singlet-oxygen generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagidullin, M V; Nikolaev, V D; Svistun, M I

2005-10-31

It is shown that if a supersonic oxygen-iodine ejector laser is fed by singlet oxygen from a centrifugal bubbling generator operating at a centrifugal acceleration of {approx}400g, the laser output power achieves a value 1264 W at a chemical efficiency of 24.6% for an alkaline hydrogen peroxide flow rate of 208 cm{sup 3}s{sup -1} and a specific chlorine load of 1.34 mmol s{sup -1} per square centimetre of the bubble layer. (lasers)

Does photodissociation of molecular oxygen from myoglobin and hemoglobin yield singlet oxygen?

PubMed

Lepeshkevich, Sergei V; Stasheuski, Alexander S; Parkhats, Marina V; Galievsky, Victor A; Dzhagarov, Boris M

2013-03-05

Time-resolved luminescence measurements in the near-infrared region indicate that photodissociation of molecular oxygen from myoglobin and hemoglobin does not produce detectable quantities of singlet oxygen. A simple and highly sensitive method of luminescence quantification is developed and used to determine the upper limit for the quantum yield of singlet oxygen production. The proposed method was preliminarily evaluated using model data sets and confirmed with experimental data for aqueous solutions of 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin. A general procedure for error estimation is suggested. The method is shown to provide a determination of the integral luminescence intensity in a wide range of values even for kinetics with extremely low signal-to-noise ratio. The present experimental data do not deny the possibility of singlet oxygen generation during the photodissociation of molecular oxygen from myoglobin and hemoglobin. However, the photodissociation is not efficient to yield singlet oxygen escaped from the proteins into the surrounding medium. The upper limits for the quantum yields of singlet oxygen production in the surrounding medium after the photodissociation for oxyhemoglobin and oxymyoglobin do not exceed 3.4×10(-3) and 2.3×10(-3), respectively. On the average, no more than one molecule of singlet oxygen from every hundred photodissociated oxygen molecules can succeed in escaping from the protein matrix. Copyright © 2013 Elsevier B.V. All rights reserved.

Kinetics of oxygen species in an electrically driven singlet oxygen generator

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Torbin, A. P.; Pershin, A. A.; Mikheyev, P. A.; Heaven, M. C.

2015-12-01

The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O3(υ) formed in O + O2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O2(a1Δ), oxygen atom removal and ozone formation. It is shown that the process O3(υ ⩾ 2) + O2(a1Δ) → 2O2 + O is the main O2(a1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O2(a1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

Efficacy of photodynamic therapy against Streptococcus mutans biofilm: Role of singlet oxygen.

PubMed

Misba, Lama; Zaidi, Sahar; Khan, Asad U

2018-06-01

In photodynamic therapy (PDT), killing is entirely based on the ROS generation and among different types of ROS generated during PDT, singlet oxygen is considered as the most potential as illustrated in many studies and therefore it is predominantly responsible for photodamage and cytotoxic reactions. The aim of this study was to check whether singlet oxygen (Type II photochemistry) is more potential than free radicals (Type I photochemistry) against Streptococcus mutans biofilm. We have taken two phenothiazinium dyes i.e. toluidine blue O (TBO) and new methylene blue (NMB). TBO was found to have better antibacterial as well as antibiofilm effect than NMB. Antibacterial effect was evaluated by colony forming unit while antibiofilm action by crystal violet and congo red binding assays. We have also evaluated the disruption of preformed biofilm by biofilm reduction assay, confocal laser electron and scanning electron microscopy. More singlet oxygen production was detected in case of TBO than NMB while more Free radical (HO) was produced by NMB than TBO. TBO showed better antibacterial as well as antibiofilm effect than NMB so; we conclude that potency of a photosensitizer is correlated with the capability to produce singlet oxygen. Copyright © 2018 Elsevier B.V. All rights reserved.

Time-resolved spectral analysis of Radachlorin luminescence in water

NASA Astrophysics Data System (ADS)

Belik, V. P.; Gadzhiev, I. M.; Semenova, I. V.; Vasyutinskii, O. S.

2017-05-01

We report results of spectral- and time-resolved study of Radachlorin photosensitizer luminescence in water in the spectral range of 950-1350nm and for determination of the photosensitizer triplet state and the singlet oxygen lifetimes responsible for singlet oxygen generation and degradation. At any wavelength within the explored spectral range the luminescence decay contained two major contributions: a fast decay at the ns time scale and a slow evolution at the μs time scale. The fast decay was attributed to electric dipole fluorescence transitions in photosensitizer molecules and the slow evolution to intercombination phosphorescence transitions in singlet oxygen and photosensitizer molecules. Relatively high-amplitude ns peak observed at all wavelengths suggests that singlet oxygen monitoring with spectral isolation methods alone, without additional temporal resolution can be controversial. In the applied experimental conditions the total phosphorescence signal at any wavelength contained a contribution from the photosensitizer triplet state decay, while at 1274nm the singlet oxygen phosphorescence dominated. The results obtained can be used for optimization of the methods of singlet oxygen monitoring and imaging.

Spectral properties of singlet-oxygen luminescence in the IR Region at the 1Δ g → 3Σ g transition in the presence of fullerene as a photosensitizer

NASA Astrophysics Data System (ADS)

Kiselev, V. M.; Bagrov, I. V.

2017-10-01

The spectral properties of singlet-oxygen luminescence at the 1Δ g → 3Σ g transition observed using fullerene as a photosensitizer are analyzed. It is shown that the use of C60 and C70 fullerenes for singlet-oxygen generation exhibits all the main spectral regularities observed for other photosensitizers. The results of investigations in this field are summarized.

Singlet Oxygen-Induced Membrane Disruption and Serpin-Protease Balance in Vacuolar-Driven Cell Death.

PubMed

Koh, Eugene; Carmieli, Raanan; Mor, Avishai; Fluhr, Robert

2016-07-01

Singlet oxygen plays a role in cellular stress either by providing direct toxicity or through signaling to initiate death programs. It was therefore of interest to examine cell death, as occurs in Arabidopsis, due to differentially localized singlet oxygen photosensitizers. The photosensitizers rose bengal (RB) and acridine orange (AO) were localized to the plasmalemma and vacuole, respectively. Their photoactivation led to cell death as measured by ion leakage. Cell death could be inhibited by the singlet oxygen scavenger histidine in treatments with AO but not with RB In the case of AO treatment, the vacuolar membrane was observed to disintegrate. Concomitantly, a complex was formed between a vacuolar cell-death protease, RESPONSIVE TO DESSICATION-21 and its cognate cytoplasmic protease inhibitor ATSERPIN1. In the case of RB treatment, the tonoplast remained intact and no complex was formed. Over-expression of AtSerpin1 repressed cell death, only under AO photodynamic treatment. Interestingly, acute water stress showed accumulation of singlet oxygen as determined by fluorescence of Singlet Oxygen Sensor Green, by electron paramagnetic resonance spectroscopy and the induction of singlet oxygen marker genes. Cell death by acute water stress was inhibited by the singlet oxygen scavenger histidine and was accompanied by vacuolar collapse and the appearance of serpin-protease complex. Over-expression of AtSerpin1 also attenuated cell death under this mode of cell stress. Thus, acute water stress damage shows parallels to vacuole-mediated cell death where the generation of singlet oxygen may play a role. © 2016 American Society of Plant Biologists. All Rights Reserved.

Comparison of singlet oxygen threshold dose for PDT.

PubMed

Zhu, Timothy C; Liu, Baochang; Kim, Michele M; McMillan, Dayton; Liang, Xing; Finlay, Jarod C; Busch, Theresa M

2014-02-01

Macroscopic modeling of singlet oxygen ( 1 O 2 ) is of particular interest because it is the major cytotoxic agent causing biological effects for type II photosensitizers during PDT. We have developed a macroscopic model to calculate reacted singlet oxygen concentration ([1O2] rx for PDT. An in-vivo RIF tumor mouse model is used to correlate the necrosis depth to the calculation based on explicit PDT dosimetry of light fluence distribution, tissue optical properties, and photosensitizer concentrations. Inputs to the model include 4 photosensitizer specific photochemical parameters along with the apparent singlet oxygen threshold concentration. Photosensitizer specific model parameters are determined for several type II photosensitizers (Photofrin, BPD, and HPPH). The singlet oxygen threshold concentration is approximately 0.41 - 0.56 mM for all three photosensitizers studied, assuming that the fraction of singlet oxygen generated that interacts with the cell is ( f = 1). In comparison, value derived from other in-vivo mice studies is 0.4 mM for mTHPC. However, the singlet oxygen threshold doses were reported to be 7.9 and 12.1 mM for a multicell in-vitro EMT6/Ro spheroid model for mTHPC and Photofrin PDT, respectively. The sensitivity of threshold singlet oxygen dose for our experiment is examined. The possible influence of vascular vs. apoptotic cell killing mechanism on the singlet oxygen threshold dose is discussed using the BPD with different drug-light intervals 3 hrs vs. 15 min. The observed discrepancies between different experiments warrant further investigation to explain the cause of the difference.

Comparison of singlet oxygen threshold dose for PDT

PubMed Central

Zhu, Timothy C; Liu, Baochang; Kim, Michele M.; McMillan, Dayton; Liang, Xing; Finlay, Jarod C.; Busch, Theresa M.

2015-01-01

Macroscopic modeling of singlet oxygen (1O2) is of particular interest because it is the major cytotoxic agent causing biological effects for type II photosensitizers during PDT. We have developed a macroscopic model to calculate reacted singlet oxygen concentration ([1O2]rx for PDT. An in-vivo RIF tumor mouse model is used to correlate the necrosis depth to the calculation based on explicit PDT dosimetry of light fluence distribution, tissue optical properties, and photosensitizer concentrations. Inputs to the model include 4 photosensitizer specific photochemical parameters along with the apparent singlet oxygen threshold concentration. Photosensitizer specific model parameters are determined for several type II photosensitizers (Photofrin, BPD, and HPPH). The singlet oxygen threshold concentration is approximately 0.41 – 0.56 mM for all three photosensitizers studied, assuming that the fraction of singlet oxygen generated that interacts with the cell is (f = 1). In comparison, value derived from other in-vivo mice studies is 0.4 mM for mTHPC. However, the singlet oxygen threshold doses were reported to be 7.9 and 12.1 mM for a multicell in-vitro EMT6/Ro spheroid model for mTHPC and Photofrin PDT, respectively. The sensitivity of threshold singlet oxygen dose for our experiment is examined. The possible influence of vascular vs. apoptotic cell killing mechanism on the singlet oxygen threshold dose is discussed using the BPD with different drug-light intervals 3 hrs vs. 15 min. The observed discrepancies between different experiments warrant further investigation to explain the cause of the difference. PMID:25999651

Singlet Oxygen-Induced Membrane Disruption and Serpin-Protease Balance in Vacuolar-Driven Cell Death1[OPEN

PubMed Central

Carmieli, Raanan; Mor, Avishai; Fluhr, Robert

2016-01-01

Singlet oxygen plays a role in cellular stress either by providing direct toxicity or through signaling to initiate death programs. It was therefore of interest to examine cell death, as occurs in Arabidopsis, due to differentially localized singlet oxygen photosensitizers. The photosensitizers rose bengal (RB) and acridine orange (AO) were localized to the plasmalemma and vacuole, respectively. Their photoactivation led to cell death as measured by ion leakage. Cell death could be inhibited by the singlet oxygen scavenger histidine in treatments with AO but not with RB. In the case of AO treatment, the vacuolar membrane was observed to disintegrate. Concomitantly, a complex was formed between a vacuolar cell-death protease, RESPONSIVE TO DESSICATION-21 and its cognate cytoplasmic protease inhibitor ATSERPIN1. In the case of RB treatment, the tonoplast remained intact and no complex was formed. Over-expression of AtSerpin1 repressed cell death, only under AO photodynamic treatment. Interestingly, acute water stress showed accumulation of singlet oxygen as determined by fluorescence of Singlet Oxygen Sensor Green, by electron paramagnetic resonance spectroscopy and the induction of singlet oxygen marker genes. Cell death by acute water stress was inhibited by the singlet oxygen scavenger histidine and was accompanied by vacuolar collapse and the appearance of serpin-protease complex. Over-expression of AtSerpin1 also attenuated cell death under this mode of cell stress. Thus, acute water stress damage shows parallels to vacuole-mediated cell death where the generation of singlet oxygen may play a role. PMID:26884487

Dual Functioning Thieno-Pyrrole Fused BODIPY Dyes for NIR Optical Imaging and Photodynamic Therapy: Singlet Oxygen Generation without Heavy Halogen Atom Assistance.

PubMed

Watley, Ryan L; Awuah, Samuel G; Bio, Moses; Cantu, Robert; Gobeze, Habtom B; Nesterov, Vladimir N; Das, Sushanta K; D'Souza, Francis; You, Youngjae

2015-06-01

We discovered a rare phenomenon wherein a thieno-pyrrole fused BODIPY dye (SBDPiR690) generates singlet oxygen without heavy halogen atom substituents. SBDPiR690 generates both singlet oxygen and fluorescence. To our knowledge, this is the first example of such a finding. To establish a structure-photophysical property relationship, we prepared SBDPiR analogs with electron-withdrawing groups at the para-position of the phenyl groups. The electron-withdrawing groups increased the HOMO-LUMO energy gap and singlet oxygen generation. Among the analogs, SBDPiR688, a CF3 analog, had an excellent dual functionality of brightness (82290 m(-1)  cm(-1) ) and phototoxic power (99170 m(-1)  cm(-1) ) comparable to those of Pc 4, due to a high extinction coefficient (211 000 m(-1)  cm(-1) ) and balanced decay (Φflu =0.39 and ΦΔ =0.47). The dual functionality of the lead compound SBDPiR690 was successfully applied to preclinical optical imaging and for PDT to effectively control a subcutaneous tumor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The generation of singlet oxygen (o(2)) by the nitrodiphenyl ether herbicide oxyfluorfen is independent of photosynthesis.

PubMed

Haworth, P; Hess, F D

1988-03-01

The mechanism of action of the p-nitrodiphenyl ether herbicides has remained ambiguous because of conflicting reports in the literature. The diphenyl ether herbicide oxyfluorfen causes a light induced consumption of oxygen which resembles the electron acceptor reaction of paraquat. However, this reaction is not linked to the transport of electrons through photosystem I. This conclusion is based on the observation that the rate of oxygen consumption, in the presence of oxyfluorfen, does not demonstrate a first order rate dependence on light intensity. Using the bleaching of N,N-dimethyl p-nitrosoaniline as a specific detector of singlet oxygen, we demonstrate that oxyfluorfen is a potent generator of this toxic radical. The production of singlet oxygen occurs in the presence of inhibitors of photosynthetic electron transport (oxyfluorfen at 10(-4) molar and paraquat) and also under temperature conditions (3 degrees C) which prevent electron transport. This light induced reaction results in oxygen consumption and is the primary cause of lethality for oxyfluorfen. The production of singlet oxygen occurs rapidly and at low herbicide concentrations (10(-9) molar). The reaction occurs without photosynthetic electron transport but does require an intact thylakoid membrane.

The Generation of Singlet Oxygen (1O2) by the Nitrodiphenyl Ether Herbicide Oxyfluorfen Is Independent of Photosynthesis

PubMed Central

Haworth, Phil; Hess, F. Dan

1988-01-01

The mechanism of action of the p-nitrodiphenyl ether herbicides has remained ambiguous because of conflicting reports in the literature. The diphenyl ether herbicide oxyfluorfen causes a light induced consumption of oxygen which resembles the electron acceptor reaction of paraquat. However, this reaction is not linked to the transport of electrons through photosystem I. This conclusion is based on the observation that the rate of oxygen consumption, in the presence of oxyfluorfen, does not demonstrate a first order rate dependence on light intensity. Using the bleaching of N,N-dimethyl p-nitrosoaniline as a specific detector of singlet oxygen, we demonstrate that oxyfluorfen is a potent generator of this toxic radical. The production of singlet oxygen occurs in the presence of inhibitors of photosynthetic electron transport (oxyfluorfen at 10−4 molar and paraquat) and also under temperature conditions (3°C) which prevent electron transport. This light induced reaction results in oxygen consumption and is the primary cause of lethality for oxyfluorfen. The production of singlet oxygen occurs rapidly and at low herbicide concentrations (10−9 molar). The reaction occurs without photosynthetic electron transport but does require an intact thylakoid membrane. PMID:16665968

Prospects of in vivo singlet oxygen luminescence monitoring: Kinetics at different locations on living mice.

PubMed

Pfitzner, Michael; Schlothauer, Jan C; Bastien, Estelle; Hackbarth, Steffen; Bezdetnaya, Lina; Lassalle, Henri-Pierre; Röder, Beate

2016-06-01

Singlet oxygen observation is considered a valuable tool to assess and optimize PDT treatment. In complex systems, such as tumors in vivo, only the direct, time-resolved singlet oxygen luminescence detection can give reliable information about generation and interaction of singlet oxygen. Up to now, evaluation of kinetics was not possible due to insufficient signal-to-noise ratio. Here we present high signal-to-noise ratio singlet oxygen luminescence kinetics obtained in mouse tumor model under PDT relevant conditions. A highly optimized system based on a custom made laser diode excitation source and a high aperture multi-furcated fiber, utilizing a photomultiplier tube with a multi photon counting device was used. Luminescence kinetics with unsurpassed signal-to-noise ratio were gained from tumor bearing nude mice in vivo upon topic application, subcutaneous injection as well as intravenous injection of different photosensitizers (chlorin e6 and dendrimer formulations of chlorin e6). Singlet oxygen kinetics in appropriate model systems are discussed to facilitate the interpretation of complex kinetics obtained from in vivo tumor tissue. This is the first study addressing the complexity of singlet oxygen luminescence kinetics in tumor tissue. At present, further investigations are needed to fully explain the processes involved. Nevertheless, the high signal-to-noise ratio proves the applicability of direct time-resolved singlet oxygen luminescence detection as a prospective tool for monitoring photodynamic therapy. Copyright © 2016 Elsevier B.V. All rights reserved.

Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer.

PubMed

Nardi, Giacomo; Manet, Ilse; Monti, Sandra; Miranda, Miguel A; Lhiaubet-Vallet, Virginie

2014-12-01

For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP(+) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies. Copyright © 2014 Elsevier Inc. All rights reserved.

Development of advanced generator of singlet oxygen for a COIL

NASA Astrophysics Data System (ADS)

Kodymová, Jarmila; Špalek, Otomar; Jirásek, Vít; Čenský, Miroslav; Hrubý, Jan

2006-05-01

The generator of singlet oxygen (SOG) remains still a challenge for a chemical oxygen-iodine laser (COIL). Hitherto, only chemical generators based on the gas-liquid reaction system (chlorine-basic hydrogen peroxide) can supply singlet oxygen, O II(1Δ), in enough high yields and at pressures to maintain operation of the high power supersonic COIL facilities. Employing conventional generators of jet-type or rotating disc-type makes often problems resulting mainly from liquid droplets entrained by an O II (1Δ) stream into the laser cavity, and a limited scalability of these generators. Advanced generator concepts investigated currently are based on two different approaches: (i)O II(1Δ) generation by the electrical discharge in various configurations, eliminating thus a liquid chemistry, and (ii) O II(1Δ) generation by the conventional chemistry in novel configurations offering the SOG efficiency increase and eliminating drawbacks of existing devices. One of the advanced concepts of chemical generator - a spray SOG with centrifugal separation of gasliquid phases - has been proposed and investigated in our laboratory. In this paper we present a description of the generator principle, some essential results of theoretical estimations, and interim experimental results obtained with the spray SOG.

A Comparison of Singlet Oxygen Explicit Dosimetry (SOED) and Singlet Oxygen Luminescence Dosimetry (SOLD) for Photofrin-Mediated Photodynamic Therapy

PubMed Central

Kim, Michele M.; Penjweini, Rozhin; Gemmell, Nathan R.; Veilleux, Israel; McCarthy, Aongus; Buller, Gerald S.; Hadfield, Robert H.; Wilson, Brian C.; Zhu, Timothy C.

2016-01-01

Accurate photodynamic therapy (PDT) dosimetry is critical for the use of PDT in the treatment of malignant and nonmalignant localized diseases. A singlet oxygen explicit dosimetry (SOED) model has been developed for in vivo purposes. It involves the measurement of the key components in PDT—light fluence (rate), photosensitizer concentration, and ground-state oxygen concentration ([3O2])—to calculate the amount of reacted singlet oxygen ([1O2]rx), the main cytotoxic component in type II PDT. Experiments were performed in phantoms with the photosensitizer Photofrin and in solution using phosphorescence-based singlet oxygen luminescence dosimetry (SOLD) to validate the SOED model. Oxygen concentration and photosensitizer photobleaching versus time were measured during PDT, along with direct SOLD measurements of singlet oxygen and triplet state lifetime (τΔ and τt), for various photosensitizer concentrations to determine necessary photophysical parameters. SOLD-determined cumulative [1O2]rx was compared to SOED-calculated [1O2]rx for various photosensitizer concentrations to show a clear correlation between the two methods. This illustrates that explicit dosimetry can be used when phosphorescence-based dosimetry is not feasible. Using SOED modeling, we have also shown evidence that SOLD-measured [1O2]rx using a 523 nm pulsed laser can be used to correlate to singlet oxygen generated by a 630 nm laser during a clinical malignant pleural mesothelioma (MPM) PDT protocol by using a conversion formula. PMID:27929427

A Comparison of Singlet Oxygen Explicit Dosimetry (SOED) and Singlet Oxygen Luminescence Dosimetry (SOLD) for Photofrin-Mediated Photodynamic Therapy.

PubMed

Kim, Michele M; Penjweini, Rozhin; Gemmell, Nathan R; Veilleux, Israel; McCarthy, Aongus; Buller, Gerald S; Hadfield, Robert H; Wilson, Brian C; Zhu, Timothy C

2016-12-06

Accurate photodynamic therapy (PDT) dosimetry is critical for the use of PDT in the treatment of malignant and nonmalignant localized diseases. A singlet oxygen explicit dosimetry (SOED) model has been developed for in vivo purposes. It involves the measurement of the key components in PDT-light fluence (rate), photosensitizer concentration, and ground-state oxygen concentration ([³ O ₂])-to calculate the amount of reacted singlet oxygen ([¹ O ₂] rx ), the main cytotoxic component in type II PDT. Experiments were performed in phantoms with the photosensitizer Photofrin and in solution using phosphorescence-based singlet oxygen luminescence dosimetry (SOLD) to validate the SOED model. Oxygen concentration and photosensitizer photobleaching versus time were measured during PDT, along with direct SOLD measurements of singlet oxygen and triplet state lifetime ( τ Δ and τ t ), for various photosensitizer concentrations to determine necessary photophysical parameters. SOLD-determined cumulative [¹ O ₂] rx was compared to SOED-calculated [¹ O ₂] rx for various photosensitizer concentrations to show a clear correlation between the two methods. This illustrates that explicit dosimetry can be used when phosphorescence-based dosimetry is not feasible. Using SOED modeling, we have also shown evidence that SOLD-measured [¹ O ₂] rx using a 523 nm pulsed laser can be used to correlate to singlet oxygen generated by a 630 nm laser during a clinical malignant pleural mesothelioma (MPM) PDT protocol by using a conversion formula.

Improved photocatalytic degradation of Orange G using hybrid nanofibers

NASA Astrophysics Data System (ADS)

Ledwaba, Mpho; Masilela, Nkosiphile; Nyokong, Tebello; Antunes, Edith

2017-05-01

Functionalised electrospun polyamide-6 (PA-6) nanofibres incorporating gadolinium oxide nanoparticles conjugated to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) as the sensitizer were prepared for the photocatalytic degradation of Orange G. Fibres incorporating the phthalocyanine alone or a mixture of the nanoparticles and phthalocyanine were also generated. The singlet oxygen-generating ability of the sensitizer was shown to be maintained within the fibre mat, with the singlet oxygen quantum yields increasing upon incorporation of the magnetic nanoparticles. Consequently, the rate of the photodegradation of Orange G was observed to increase with an increase in singlet oxygen quantum yield. A reduction in the half-lives for the functionalised nanofibres was recorded in the presence of the magnetic nanoparticles, indicating an improvement in the efficiency of the degradation process.

Phytoalexin Phenalenone Derivatives Inactivate Mosquito Larvae and Root-knot Nematode as Type-II Photosensitizer

NASA Astrophysics Data System (ADS)

Song, Runjiang; Feng, Yian; Wang, Donghui; Xu, Zhiping; Li, Zhong; Shao, Xusheng

2017-02-01

Phytoalexins phenalenones (PNs) are phytochemicals biosynthesized inside the plant in responsive to exterior threat. PNs are excellent type-II photosensitizers, which efficiently produce singlet oxygen upon light irradiation. Based on the core functional structure of PNs, novel PN derivatives were synthesized here and their singlet oxygen generating abilities and their phototoxicity were evaluated. At the presence of light, these PNs have photoinduced toxicity towards Aedes albopictus larvae and nematode Meloidogyne incognita, while the activity lost in the dark. The obvious tissue damage was observed on the treated mosquito larvae and nematode due to the generation of singlet oxygen. Our results revealed the potential of phenalenones as photoactivated agents for mosquito and root-knot nematode management together with light.

Interaction of plasmalogens and their diacyl analogs with singlet oxygen in selected model systems

PubMed Central

Broniec, Agnieszka; Klosinski, Radoslaw; Pawlak, Anna; Wrona-Krol, Marta; Thompson, David; Sarna, Tadeusz

2011-01-01

Plasmalogens (Plg) are phospholipids containing vinyl ether linkage at the sn-1 position of the glycerophospholipid backbone. In spite of being quite abundant in humans, the biological role of plasmalogens remains speculative. It has been postulated that plasmalogens are physiological antioxidants with the vinyl ether functionality serving as sacrificial trap for free radicals and singlet oxygen. However, no quantitative data on the efficiency of plasmalogens to scavenge these reactive species are available. In this study, rate constants of quenching of singlet oxygen, generated by photosensitized energy transfer, by several plasmalogens and, for comparison, by their diacyl analogs, were determined by time-resolved detection of phosphorescence at 1270 nm. Relative rates of the interaction of singlet oxygen, with plasmalogens and other lipids in solution and liposomal membranes were measured by electron paramagnetic resonance oximetry and product analysis, employing HPLC-EC detection of cholesterol hydroperoxides and iodometric assay of lipid hydroperoxides. Results show that singlet oxygen interacts with plasmalogens significantly faster than with the other lipids, with he corresponding rate constants being by one-two orders of magnitude greater. The quenching of singlet oxygen by plasmalogens is mostly reactive in nature and results from its preferential interaction with the vinyl ether bond. The data suggest that plasmalogens could protect unsaturated membrane lipids against oxidation induced by singlet oxygen, providing that the oxidation products are not excessively cytotoxic. PMID:21236336

Solar generation and storage of O2 (a 1 delta g)

NASA Technical Reports Server (NTRS)

Twarowski, Allen J.; Dao, Phan; Good, Lisa A.

1988-01-01

An investigation was performed of the technical steps required to design a solar powered oxygen-iodine laser. Singlet delta oxygen is formed upon transfer of energy from selected photoexcited dye molecules to ground state molecular oxygen and then is concentrated and stored as an endoperoxide by reaction with an aromatic hydrocarbon. The endoperoxide, when heated, releases singlet oxygen in high yield thus providing a regenerable source of laser fuel. Energy transfer from dye molecules to molecular oxygen was investigated. When dye molecules were adsorbed to polymer substrates it was observed that the dye became embedded in the polymer matrix. Porphin dyes were incorporated into films of 1,4-dimethyl-2-poly(vinylnaphthalene), 2PVN. An endoperoxide was formed when porphin-doped 2PVN was exposed to visible radiation. This demonstrates the possibility of generating singlet oxygen using solar energy and concentrating and storing it in one simple step. Transport of energy by exciton migration in polycrystalline dye films was also investigated.

Light-induced generation of singlet oxygen by naked gold nanoparticles and its implications to cancer cell phototherapy.

PubMed

Pasparakis, George

2013-12-20

Generation of singlet oxygen by direct irradiation of naked gold nanoparticles is observed using either continuous wave or pulsed laser sources. The underlying mechanism involves plasmon- and hot-electron-mediated reaction pathways and (1) O2 seems to significantly amplify the overall death rates during photothermal treatment of cancer cell lines in vitro. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revealing mechanisms of selective, concentration-dependent potentials of 4-hydroxy-2-nonenal to induce apoptosis in cancer cells through inactivation of membrane-associated catalase.

PubMed

Bauer, Georg; Zarkovic, Neven

2015-04-01

Tumor cells generate extracellular superoxide anions and are protected against superoxide anion-mediated intercellular apoptosis-inducing signaling by the expression of membrane-associated catalase. 4-Hydroxy-2-nonenal (4-HNE), a versatile second messenger generated during lipid peroxidation, has been shown to induce apoptosis selectively in malignant cells. The findings described in this paper reveal the strong, concentration-dependent potential of 4-HNE to specifically inactivate extracellular catalase of tumor cells both indirectly and directly and to consequently trigger apoptosis in malignant cells through superoxide anion-mediated intercellular apoptosis-inducing signaling. Namely, 4-HNE caused apoptosis selectively in NOX1-expressing tumor cells through inactivation of their membrane-associated catalase, thus reactivating subsequent intercellular signaling through the NO/peroxynitrite and HOCl pathways, followed by the mitochondrial pathway of apoptosis. Concentrations of 4-HNE of 1.2 µM and higher directly inactivated membrane-associated catalase of tumor cells, whereas at lower concentrations, 4-HNE triggered a complex amplificatory pathway based on initial singlet oxygen formation through H2O2 and peroxynitrite interaction. Singlet-oxygen-dependent activation of the FAS receptor and caspase-8 increased superoxide anion generation by NOX1 and amplification of singlet oxygen generation, which allowed singlet-oxygen-dependent inactivation of catalase. 4-HNE and singlet oxygen cooperate in complex autoamplificatory loops during this process. The finding of these novel anticancer pathways may be useful for understanding the role of 4-HNE in the control of malignant cells and for the optimization of ROS-dependent therapeutic approaches including antioxidant treatments. Copyright © 2015 Elsevier Inc. All rights reserved.

Reactive oxygen species generation in aqueous solutions containing GdVO4:Eu3+ nanoparticles and their complexes with methylene blue

NASA Astrophysics Data System (ADS)

Hubenko, Kateryna; Yefimova, Svetlana; Tkacheva, Tatyana; Maksimchuk, Pavel; Borovoy, Igor; Klochkov, Vladimir; Kavok, Nataliya; Opolonin, Oleksander; Malyukin, Yuri

2018-04-01

It this letter, we report the study of free radicals and reactive oxygen species (ROS) generation in water solutions containing gadolinium orthovanadate GdVO4:Eu3+ nanoparticles (VNPs) and their complexes with methylene blue (MB) photosensitizer. The catalytic activity was studied under UV-Vis and X-ray irradiation by three methods (conjugated dienes test, OH· radical, and singlet oxygen detection). It has been shown that the VNPs-MB complexes reveal high efficiency of ROS generation under UV-Vis irradiation associated with both high efficiency of OH· radicals generation by VNPs and singlet oxygen generation by MB due to nonradiative excitation energy transfer from VNPs to MB molecules. Contrary to that under X-ray irradiation, the strong OH . radicals scavenging by VNPs has been observed.

Reactive oxygen species generation in aqueous solutions containing GdVO4:Eu3+ nanoparticles and their complexes with methylene blue.

PubMed

Hubenko, Kateryna; Yefimova, Svetlana; Tkacheva, Tatyana; Maksimchuk, Pavel; Borovoy, Igor; Klochkov, Vladimir; Kavok, Nataliya; Opolonin, Oleksander; Malyukin, Yuri

2018-04-13

It this letter, we report the study of free radicals and reactive oxygen species (ROS) generation in water solutions containing gadolinium orthovanadate GdVO 4 :Eu 3+ nanoparticles (VNPs) and their complexes with methylene blue (MB) photosensitizer. The catalytic activity was studied under UV-Vis and X-ray irradiation by three methods (conjugated dienes test, OH· radical, and singlet oxygen detection). It has been shown that the VNPs-MB complexes reveal high efficiency of ROS generation under UV-Vis irradiation associated with both high efficiency of OH· radicals generation by VNPs and singlet oxygen generation by MB due to nonradiative excitation energy transfer from VNPs to MB molecules. Contrary to that under X-ray irradiation, the strong OH . radicals scavenging by VNPs has been observed.

Comparative study of singlet oxygen production by photosensitiser dyes encapsulated in silicone: towards rational design of anti-microbial surfaces.

PubMed

Noimark, Sacha; Salvadori, Enrico; Gómez-Bombarelli, Rafael; MacRobert, Alexander J; Parkin, Ivan P; Kay, Christopher W M

2016-10-12

Surfaces with built-in antimicrobial activity have the potential to reduce hospital-acquired infections. One promising strategy is to create functionalised surfaces which, following illumination with visible light, are able to generate singlet oxygen under aerobic conditions. In contrast to antibiotics, the mechanism of bacterial kill by species derived from reactions with singlet oxygen is completely unselective, therefore offering little room for evolutionary adaptation. Here we consider five commercially available organic photosensitiser dyes encapsulated in silicone polymer that show varied antimicrobial activity. We correlate density functional theory calculations with UV-Vis spectroscopy, electron paramagnetic resonance spectroscopy and singlet oxygen production measurements in order to define and test the elements required for efficacious antimicrobial activity. Our approach forms the basis for the rational in silico design and spectroscopic screening of simple and efficient self-sterilising surfaces made from cheap, low toxicity photosensitiser dyes encapsulated in silicone.

Mitochondrial dependent oxidative stress in cell culture induced by laser radiation at 1265 nm.

PubMed

Saenko, Yury V; Glushchenko, Eugenia S; Zolotovskii, Igor O; Sholokhov, Evgeny; Kurkov, Andrey

2016-04-01

Photodynamic therapy is the main technique applied for surface carcinoma treatment. This technique employs singlet oxygen generated via a laser excited photosensitizer as a main damaging agent. However, prolonged sensitivity to intensive light, relatively low tissue penetration by activating light the cost of photosensitizer (PS) administration can limit photodynamic therapy applications. Early was reported singlet oxygen generation without photosensitizer induced by a laser irradiation at the wavelength of 1250-1270 nm. Here, we study the dynamics of oxidative stress, DNA damage, changes of mitochondrial potential, and mitochondrial mass induced by a laser at 1265 nm have been studied in HCT-116 and CHO-K cells. Laser irradiation of HCT-116 and CHO-K cells has induced a dose-dependent cell death via increasing intracellular reactive oxygen species (ROS) concentration, increase of DNA damage, decrease of mitochondrial potential, and reduced glutathione. It has been shown that, along with singlet oxygen generation, the increase of the intracellular ROS concentration induced by mitochondrial damage contributes to the damaging effect of the laser irradiation at 1265 nm.

A comparative study of the processes of generation of singlet oxygen upon irradiation of aqueous preparations on the basis of chlorin e6 and coproporphyrin III

NASA Astrophysics Data System (ADS)

Bagrov, I. V.; Belousova, I. M.; Gorelov, S. I.; Dobrun, M. V.; Kiselev, V. M.; Kislyakov, I. M.; Kris'ko, A. V.; Kris'ko, T. K.

2017-02-01

The photosensitizing ability of an agent based on chlorin e6 (Photoditazin), which is used for photodynamic diagnosis and therapy, is compared with that of a new preparation on the basis of coproporphyrin III in the environment of a phosphate buffer and a simulated biological environment (albumin solution). The efficiency of singlet-oxygen production was estimated by EPR spectroscopy and spectroscopy in the UV and visible ranges with the use of "chemical traps" of singlet oxygen. By irradiating drugs with LED emission centered at λmax = 520 nm, we determined the quantum yield of singlet-oxygen production in a buffer solution; the obtained values are 0.60 and 0.37 for chlorine and coproporphyrin, respectively. The steady-state concentration of singlet oxygen upon irradiation of solutions of the studied photosensitizers with concentrations of 12-43 μM and the density of radiation power within the 6-96 W/cm2 region was found to be in the region of 1010-1011 molecules/cm3. It is shown that the introduction into the solution of egg albumin (0.1%) reduces the sensitizing properties of the two drugs by two to three times, while the efficiencies of the preparations with respect to singlet-oxygen production become almost identical (0.19 and 0.17).

Parabanic acid is the singlet oxygen specific oxidation product of uric acid.

PubMed

Iida, Sayaka; Ohkubo, Yuki; Yamamoto, Yorihiro; Fujisawa, Akio

2017-11-01

Uric acid quenches singlet oxygen physically or reacts with it, but the oxidation product has not been previously characterized. The present study determined that the product is parabanic acid, which was confirmed by LC/TOFMS analysis. Parabanic acid was stable at acidic pH (<5.0), but hydrolyzed to oxaluric acid at neutral or alkaline pH. The total yields of parabanic acid and oxaluric acid based on consumed uric acid were ~100% in clean singlet oxygen production systems such as UVA irradiation of Rose Bengal and thermal decomposition of 3-(1,4-dihydro-1,4-epidioxy-4-methyl-1-naphthyl)propionic acid. However, the ratio of the amount of uric acid consumed to the total amount of singlet oxygen generated was less than 1/180, indicating that most of the singlet oxygen was physically quenched. The total yields of parabanic acid and oxaluric acid were high in the uric acid oxidation systems with hydrogen peroxide plus hypochlorite or peroxynitrite. They became less than a few percent in peroxyl radical-, hypochlorite- or peroxynitrite-induced oxidation of uric acid. These results suggest that parabanic acid could be an in vivo probe of singlet oxygen formation because of the wide distribution of uric acid in human tissues and extracellular spaces. In fact, sunlight exposure significantly increased human skin levels of parabanic acid.

Metal bacteriochlorins which act as dual singlet oxygen and superoxide generators.

PubMed

Fukuzumi, Shunichi; Ohkubo, Kei; Zheng, Xiang; Chen, Yihui; Pandey, Ravindra K; Zhan, Riqiang; Kadish, Karl M

2008-03-06

A series of stable free-base, Zn(II) and Pd(II) bacteriochlorins containing a fused six- or five-member diketo- or imide ring have been synthesized as good candidates for photodynamic therapy sensitizers, and their electrochemical, photophysical, and photochemical properties were examined. Photoexcitation of the palladium bacteriochlorin affords the triplet excited state without fluorescence emission, resulting in formation of singlet oxygen with a high quantum yield due to the heavy atom effect of palladium. Electrochemical studies revealed that the zinc bacteriochlorin has the smallest HOMO-LUMO gap of the investigated compounds, and this value is significantly lower than the triplet excited-state energy of the compound in benzonitrile. Such a small HOMO-LUMO gap of the zinc bacteriochlorin enables intermolecular photoinduced electron transfer from the triplet excited state to the ground state to produce both the radical cation and the radical anion. The radical anion thus produced can transfer an electron to molecular oxygen to produce superoxide anion which was detected by electron spin resonance. The same photosensitizer can also act as an efficient singlet oxygen generator. Thus, the same zinc bacteriochlorin can function as a sensitizer with a dual role in that it produces both singlet oxygen and superoxide anion in an aprotic solvent (benzonitrile).

Redox signaling and stress tolerance in plants: a focus on vitamin E.

PubMed

Miret, Javier A; Munné-Bosch, Sergi

2015-03-01

Plants are subject to specific redox processes, in which photosynthesis plays a prominent role. Chloroplasts function in light at high oxygen tensions and are enormous generators of reactive oxygen species, mainly singlet oxygen. This side product of photosynthesis inflicts damage to thylakoid membranes at high concentrations, but at the same time it is an essential component of cellular signaling. Detoxification of singlet oxygen is achieved by different means, including quenching and scavenging by tocopherols, responsible for controlling singlet oxygen levels, and the extent of lipid peroxidation in chloroplasts. Here, environmental conditions leading to excess light in chloroplasts will be used to show the importance of singlet oxygen, tocopherols, and lipid peroxidation in cell signaling. Defects in antioxidant protection (e.g., tocopherol deficiency) can lead to increased photo-oxidative damage, but also to the activation of defense pathways, illustrating the phenotypic plasticity evolved by plants to withstand stress. Most importantly, these studies show how redox signaling processes are integrated within the cell and illustrate the great capacity of plants to adapt to their environment. © 2015 New York Academy of Sciences.

Comparing the efficiency of supersonic oxygen-iodine laser with different mixing designs

NASA Astrophysics Data System (ADS)

Vyskubenko, Boris A.; Adamenkov, A. A.; Bakshin, V. V.; Efremov, V. I.; Ilyin, S. P.; Kolobyanin, Yu. V.; Krukovsky, I. M.; Kudryashov, E. A.; Moiseyev, V. B.

2003-11-01

The paper presents experimental studies of supersonic oxygen-iodine laser (OIL) using twisted-flow singlet oxygen generator (SOG) over a wide range of the singlet oxygen pressures and the buffer gas flow rates. The experiments used different designs of the nozzle unit and mixing system for singlet oxygen and iodine gas with the carrier gas (such as nitrogen or helium). For a wide range of the key parameters, the study looked at the efficiency of supersonic OIL with variation of the singlet oxygen pressure. The measurements were made for different positions of the iodine injection plane with respect to the critical cross-section (both in the subsonic part of the nozzle and in the supersonic flow). The gas pressure at the nozzle unit entry was varied from 50 to 250 Torr. The total pressure loss have been found for different mixing designs. Experimental curves are given for energy performance and chemical efficiency of the supersonic OIL as a function of the key parameters. Comparison is made between the calculated and experimental data. For the optimum conditions of OIL operation, chemical efficiency of 25-30% has been achieved.

Photophysical Properties and Singlet Oxygen Generation Efficiencies of Water-Soluble Fullerene Nanoparticles

PubMed Central

Stasheuski, Alexander S; Galievsky, Victor A; Stupak, Alexander P; Dzhagarov, Boris M; Choi, Mi Jin; Chung, Bong Hyun; Jeong, Jin Young

2014-01-01

As various fullerene derivatives have been developed, it is necessary to explore their photophysical properties for potential use in photoelectronics and medicine. Here, we address the photophysical properties of newly synthesized water-soluble fullerene-based nanoparticles and polyhydroxylated fullerene as a representative water-soluble fullerene derivative. They show broad emission band arising from a wide-range of excitation energies. It is attributed to the optical transitions from disorder-induced states, which decay in the nanosecond time range. We determine the kinetic properties of the singlet oxygen (1O2) luminescence generated by the fullerene nanoparticles and polyhydroxylated fullerene to consider the potential as photodynamic agents. Triplet state decay of the nanoparticles was longer than 1O2 lifetime in water. Singlet oxygen quantum yield of a series of the fullerene nanoparticles is comparably higher ranging from 0.15 to 0.2 than that of polyhydroxylated fullerene, which is about 0.06. PMID:24893622

Photochemical studies of a fluorescent chlorophyll catabolite--source of bright blue fluorescence in plant tissue and efficient sensitizer of singlet oxygen.

PubMed

Jockusch, Steffen; Turro, Nicholas J; Banala, Srinivas; Kräutler, Bernhard

2014-02-01

Fluorescent chlorophyll catabolites (FCCs) are fleeting intermediates of chlorophyll breakdown, which is seen as an enzyme controlled detoxification process of the chlorophylls in plants. However, some plants accumulate large amounts of persistent FCCs, such as in senescent leaves and in peels of yellow bananas. The photophysical properties of such a persistent FCC (Me-sFCC) were investigated in detail. FCCs absorb in the near UV spectral region and show blue fluorescence (max at 437 nm). The Me-sFCC fluorescence had a quantum yield of 0.21 (lifetime 1.6 ns). Photoexcited Me-sFCC intersystem crosses into the triplet state (quantum yield 0.6) and generates efficiently singlet oxygen (quantum yield 0.59). The efficient generation of singlet oxygen makes fluorescent chlorophyll catabolites phototoxic, but might also be useful as a (stress) signal and for defense of the plant tissue against infection by pathogens.

Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

NASA Astrophysics Data System (ADS)

Blacha-Grzechnik, Agata; Piwowar, Katarzyna; Krukiewicz, Katarzyna; Koscielniak, Piotr; Szuber, Jacek; Zak, Jerzy K.

2016-05-01

The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate 1O2 when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals' synthesis or in the wastewater treatment.

In-vivo singlet oxygen threshold doses for PDT

PubMed Central

Zhu, Timothy C.; Kim, Michele M.; Liang, Xing; Finlay, Jarod C.; Busch, Theresa M.

2015-01-01

Objective Dosimetry of singlet oxygen (1O2) is of particular interest because it is the major cytotoxic agent causing biological effects for type-II photosensitizers during photodynamic therapy (PDT). An in-vivo model to determine the singlet oxygen threshold dose, [1O2]rx,sh, for PDT was developed. Material and methods An in-vivo radiation-induced fibrosarcoma (RIF) tumor mouse model was used to correlate the radius of necrosis to the calculation based on explicit PDT dosimetry of light fluence distribution, tissue optical properties, and photosensitizer concentrations. Inputs to the model include five photosensitizer-specific photochemical parameters along with [1O2]rx,sh. Photosensitizer-specific model parameters were determined for benzoporphyrin derivative monoacid ring A (BPD) and compared with two other type-II photosensitizers, Photofrin® and m-tetrahydroxyphenylchlorin (mTHPC) from the literature. Results The mean values (standard deviation) of the in-vivo [1O2]rx,sh are approximately 0.56 (0.26) and 0.72 (0.21) mM (or 3.6×107 and 4.6×107 singlet oxygen per cell to reduce the cell survival to 1/e) for Photofrin® and BPD, respectively, assuming that the fraction of generated singlet oxygen that interacts with the cell is 1. While the values for the photochemical parameters (ξ, σ, g, β) used for BPD were preliminary and may need further refinement, there is reasonable confidence for the values of the singlet oxygen threshold doses. Discussion In comparison, the [1O2]rx,sh value derived from in-vivo mouse study was reported to be 0.4 mM for mTHPC-PDT. However, the singlet oxygen required per cell is reported to be 9×108 per cell per 1/e fractional kill in an in-vitro mTHPC-PDT study on a rat prostate cancer cell line (MLL cells) and is reported to be 7.9 mM for a multicell in-vitro EMT6/Ro spheroid model for mTHPC-PDT. A theoretical analysis is provided to relate the number of in-vitro singlet oxygen required per cell to reach cell killing of 1/e to in-vivo singlet oxygen threshold dose (in mM). The sensitivity of threshold singlet oxygen dose for our experiment is examined. The possible influence of vascular vs. apoptotic cell killing mechanisms on the singlet oxygen threshold dose is discussed by comparing [1O2]rx,sh for BPD with 3 hr and 15 min drug-light-intervals, with the later being known to have a dominantly vascular effect. Conclusions The experimental results of threshold singlet oxygen concentration in an in-vivo RIF tumor model for Photofrin®, BPD, and mTHPC are about 20 times smaller than those observed in vitro. These results are consistent with knowledge that factors other than singlet oxygen-mediated tumor cell killing can contribute to PDT damage in-vivo. PMID:25927018

In-vivo singlet oxygen threshold doses for PDT.

PubMed

Zhu, Timothy C; Kim, Michele M; Liang, Xing; Finlay, Jarod C; Busch, Theresa M

2015-02-01

Dosimetry of singlet oxygen ( 1 O 2 ) is of particular interest because it is the major cytotoxic agent causing biological effects for type-II photosensitizers during photodynamic therapy (PDT). An in-vivo model to determine the singlet oxygen threshold dose, [ 1 O 2 ] rx,sh , for PDT was developed. An in-vivo radiation-induced fibrosarcoma (RIF) tumor mouse model was used to correlate the radius of necrosis to the calculation based on explicit PDT dosimetry of light fluence distribution, tissue optical properties, and photosensitizer concentrations. Inputs to the model include five photosensitizer-specific photochemical parameters along with [ 1 O 2 ] rx,sh . Photosensitizer-specific model parameters were determined for benzoporphyrin derivative monoacid ring A (BPD) and compared with two other type-II photosensitizers, Photofrin ® and m-tetrahydroxyphenylchlorin (mTHPC) from the literature. The mean values (standard deviation) of the in-vivo [ 1 O 2 ] rx,sh are approximately 0.56 (0.26) and 0.72 (0.21) mM (or 3.6×10 7 and 4.6×10 7 singlet oxygen per cell to reduce the cell survival to 1/e) for Photofrin ® and BPD, respectively, assuming that the fraction of generated singlet oxygen that interacts with the cell is 1. While the values for the photochemical parameters (ξ, σ, g , β) used for BPD were preliminary and may need further refinement, there is reasonable confidence for the values of the singlet oxygen threshold doses. In comparison, the [ 1 O 2 ] rx,sh value derived from in-vivo mouse study was reported to be 0.4 mM for mTHPC-PDT. However, the singlet oxygen required per cell is reported to be 9×10 8 per cell per 1/ e fractional kill in an in-vitro mTHPC-PDT study on a rat prostate cancer cell line (MLL cells) and is reported to be 7.9 mM for a multicell in-vitro EMT6/Ro spheroid model for mTHPC-PDT. A theoretical analysis is provided to relate the number of in-vitro singlet oxygen required per cell to reach cell killing of 1/ e to in-vivo singlet oxygen threshold dose (in mM). The sensitivity of threshold singlet oxygen dose for our experiment is examined. The possible influence of vascular vs. apoptotic cell killing mechanisms on the singlet oxygen threshold dose is discussed by comparing [ 1 O 2 ] rx,sh for BPD with 3 hr and 15 min drug-light-intervals, with the later being known to have a dominantly vascular effect. The experimental results of threshold singlet oxygen concentration in an in-vivo RIF tumor model for Photofrin ® , BPD, and mTHPC are about 20 times smaller than those observed in vitro . These results are consistent with knowledge that factors other than singlet oxygen-mediated tumor cell killing can contribute to PDT damage in-vivo .

Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals.

PubMed

Komaszylo Née Siedlecka, Joanna; Kania, Magdalena; Masnyk, Marek; Cmoch, Piotr; Lozinska, Iwona; Czarnocki, Zbigniew; Skorupinska-Tudek, Karolina; Danikiewicz, Witold; Swiezewska, Ewa

2016-02-01

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents--reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol-2 and -10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy-, peroxy- and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI-MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI-MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.

Regulation of a polyamine transporter by the conserved 3′ UTR-derived sRNA SorX confers resistance to singlet oxygen and organic hydroperoxides in Rhodobacter sphaeroides

PubMed Central

Peng, Tao; Berghoff, Bork A.; Oh, Jeong-Il; Weber, Lennart; Schirmer, Jasmin; Schwarz, Johannes; Glaeser, Jens; Klug, Gabriele

2016-01-01

ABSTRACT Singlet oxygen is generated by bacteriochlorophylls when light and oxygen are simultaneously present in Rhodobacter sphaeroides. Singlet oxygen triggers a specific response that is partly regulated by the alternative sigma factor RpoHI/HII. The sRNA RSs2461 has previously been identified as an RpoHI/HII-dependent sRNA and is derived from the 3′ UTR of the mRNA for an OmpR-type transcriptional regulator. Similar to the RpoHI/HII-dependent CcsR and SorY sRNAs, RSs2461 affects the resistance of R. sphaeroides against singlet oxygen and was therefore renamed here SorX. Furthermore, SorX has a strong impact on resistance against organic hydroperoxides that usually occur as secondary damages downstream of singlet oxygen. The 75-nt SorX 3′ fragment, which is generated by RNase E cleavage and highly conserved among related species, represents the functional entity. A target search identified potA mRNA, which encodes a subunit of a polyamine transporter, as a direct SorX target and stress resistance via SorX could be linked to potA. The PotABCD transporter is an uptake system for spermidine in E. coli. While spermidine is generally described as beneficial during oxidative stress, we observed significantly increased sensitivity of R. sphaeroides to organic hydroperoxides in the presence of spermidine. We therefore propose that the diminished import of spermidine, due to down-regulation of potA by SorX, counteracts oxidative stress. Together with results from other studies this underlines the importance of regulated transport to bacterial stress defense. PMID:27420112

Regulation of a polyamine transporter by the conserved 3' UTR-derived sRNA SorX confers resistance to singlet oxygen and organic hydroperoxides in Rhodobacter sphaeroides.

PubMed

Peng, Tao; Berghoff, Bork A; Oh, Jeong-Il; Weber, Lennart; Schirmer, Jasmin; Schwarz, Johannes; Glaeser, Jens; Klug, Gabriele

2016-10-02

Singlet oxygen is generated by bacteriochlorophylls when light and oxygen are simultaneously present in Rhodobacter sphaeroides. Singlet oxygen triggers a specific response that is partly regulated by the alternative sigma factor RpoHI/HII. The sRNA RSs2461 has previously been identified as an RpoHI/HII-dependent sRNA and is derived from the 3' UTR of the mRNA for an OmpR-type transcriptional regulator. Similar to the RpoHI/HII-dependent CcsR and SorY sRNAs, RSs2461 affects the resistance of R. sphaeroides against singlet oxygen and was therefore renamed here SorX. Furthermore, SorX has a strong impact on resistance against organic hydroperoxides that usually occur as secondary damages downstream of singlet oxygen. The 75-nt SorX 3' fragment, which is generated by RNase E cleavage and highly conserved among related species, represents the functional entity. A target search identified potA mRNA, which encodes a subunit of a polyamine transporter, as a direct SorX target and stress resistance via SorX could be linked to potA. The PotABCD transporter is an uptake system for spermidine in E. coli. While spermidine is generally described as beneficial during oxidative stress, we observed significantly increased sensitivity of R. sphaeroides to organic hydroperoxides in the presence of spermidine. We therefore propose that the diminished import of spermidine, due to down-regulation of potA by SorX, counteracts oxidative stress. Together with results from other studies this underlines the importance of regulated transport to bacterial stress defense.

Cholecystokinin 1 Receptor - A Unique G Protein-Coupled Receptor Activated by Singlet Oxygen (GPCR-ABSO).

PubMed

Jiang, Hong Ning; Li, Yuan; Jiang, Wen Yi; Cui, Zong Jie

2018-01-01

Plasma membrane-delimited generation of singlet oxygen by photodynamic action with photosensitizer sulfonated aluminum phthalocyanine (SALPC) activates cholecystokinin 1 receptor (CCK1R) in pancreatic acini. Whether CCK1R retains such photooxidative singlet oxygen activation properties in other environments is not known. Genetically encoded protein photosensitizers KillerRed or mini singlet oxygen generator (miniSOG) were expressed in pancreatic acinar tumor cell line AR4-2J, CCK1R, KillerRed or miniSOG were expressed in HEK293 or CHO-K1 cells. Cold light irradiation (87 mW⋅cm -2 ) was applied to photosensitizer-expressing cells to examine photodynamic activation of CCK1R by Fura-2 fluorescent calcium imaging. When CCK1R was transduced into HEK293 cells which lack endogenous CCK1R, photodynamic action with SALPC was found to activate CCK1R in CCK1R-HEK293 cells. When KillerRed or miniSOG were transduced into AR4-2J which expresses endogenous CCK1R, KillerRed or miniSOG photodynamic action at the plasma membrane also activated CCK1R. When fused KillerRed-CCK1R was transduced into CHO-K1 cells, light irradiation activated the fused CCK1R leading to calcium oscillations. Therefore KillerRed either expressed independently, or fused with CCK1R can both activate CCK1R photodynamically. It is concluded that photodynamic singlet oxygen activation is an intrinsic property of CCK1R, independent of photosensitizer used, or CCK1R-expressing cell types. Photodynamic singlet oxygen CCK1R activation after transduction of genetically encoded photosensitizer in situ may provide a convenient way to verify intrinsic physiological functions of CCK1R in multiple CCK1R-expressing cells and tissues, or to actuate CCK1R function in CCK1R-expressing and non-expressing cell types after transduction with fused KillerRed-CCK1R.

Theoretical study of singlet oxygen molecule generation via an exciplex with valence-excited thiophene.

PubMed

Sumita, Masato; Morihashi, Kenji

2015-02-05

Singlet-oxygen [O2((1)Δg)] generation by valence-excited thiophene (TPH) has been investigated using multireference Møller-Plesset second-order perturbation (MRMP2) theory of geometries optimized at the complete active space self-consistent field (CASSCF) theory level. Our results indicate that triplet TPH(1(3)B2) is produced via photoinduced singlet TPH(2(1)A1) because 2(1)A1 TPH shows a large spin-orbit coupling constant with the first triplet excited state (1(3)B2). The relaxed TPH in the 1(3)B2 state can form an exciplex with O2((3)Σg(-)) because this exciplex is energetically more stable than the relaxed TPH. The formation of the TPH(1(3)B2) exciplex with O2((3)Σg(-)) whose total spin multiplicity is triplet (T1 state) increases the likelihood of transition from the T1 state to the singlet ground or first excited singlet state. After the transition, O2((1)Δg) is emitted easily although the favorable product is that from a 2 + 4 cycloaddition reaction.

Increasing the endogenous NO level causes catalase inactivation and reactivation of intercellular apoptosis signaling specifically in tumor cells

PubMed Central

Bauer, Georg

2015-01-01

Tumor cells generate extracellular superoxide anions and are protected against intercellular apoptosis-inducing HOCl- and NO/peroxynitrite signaling through the expression of membrane-associated catalase. This enzyme decomposes H2O2 and thus prevents HOCl synthesis. It efficiently interferes with NO/peroxynitrite signaling through oxidation of NO and decomposition of peroxynitrite. The regulatory potential of catalase at the crosspoint of ROS and RNS chemical biology, as well as its high local concentration on the outside of the cell membrane of tumor cells, establish tight control of intercellular signaling and thus prevent tumor cell apoptosis. Therefore, inhibition of catalase or its inactivation by singlet oxygen reactivate intercellular apoptosis-inducing signaling. Nitric oxide and peroxynitrite are connected with catalase in multiple and meaningful ways, as (i) NO can be oxidated by compound I of catalase, (ii) NO can reversibly inhibit catalase, (iii) peroxynitrite can be decomposed by catalase and (iv) the interaction between peroxynitrite and H2O2 leads to the generation of singlet oxygen that inactivates catalase. Therefore, modulation of the concentration of free NO through addition of arginine, inhibition of arginase, induction of NOS expression or inhibition of NO dioxygenase triggers an autoamplificatory biochemical cascade that is based on initial formation of singlet oxygen, amplification of superoxide anion/H2O2 and NO generation through singlet oxygen dependent stimulation of the FAS receptor and caspase-8. Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling. This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors. The latter aspect is explicitely studied for the interaction between catalase inhibiting acetylsalicylic acid and an NO donor. It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential. Our data open novel approaches for rational tumor therapy based on specific ROS signaling and its control in tumor cells. PMID:26342455

Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

PubMed

Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

2006-03-01

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water

PubMed Central

Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

2012-01-01

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1Δg)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O2 gas to the reactor chambers. In the presence of O2, singlet oxygen was generated by illuminating the sensitizer particles with 669-nm light from an optical fiber coupled to the top of the reactor. The generated 1O2 was transported through the membrane by the O2 stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (either 9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, and N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that 1O2 transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow, it arose only from 1O2-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves 1O2 mass transfer and solvation, where smaller bubbles provide better penetration of 1O2 into the flowing stream due to higher surface-to-volume contact between the probe molecules and 1O2. PMID:22260325

UVA Photoirradiation of Oxygenated Benz[a]anthracene and 3-Methylcholanthene - Generation of Singlet Oxygen and Induction of Lipid Peroxidation

PubMed Central

Yin, Jun-Jie; Xia, Qingsu; Cherng, Shu-Hui; Tang, I-Wah; Fu, Peter P.; Lin, Ge; Yu, Hongtao; Herreño Sáenz, Diógenes

2008-01-01

Polycyclic aromatic hydrocarbons (PAHs) are widespread genotoxic environmental pollutants and potentially pose a health risk to humans. Although the biological and toxicological activities, including metabolism, mutagenicity, and carcinogenicity, of PAHs have been thoroughly studied, their phototoxicity and photo-induced biological activity have not been well examined. We have long been interested in phototoxicity of PAHs and their derivatives induced by irradiation with UV light. In this paper we report the photoirradiation of a series of oxygenated benz[a]anthracene (BA) and 3-methylcholanthene (3-MC) by UVA light in the presence of a lipid, methyl linoleate. The studied PAHs include 2-hydroxy-BA (2-OH-BA), 3-hydroxy-BA (3-OH-BA), 5-hydroxymethyl-BA (5-CH2OH-BA), 7-hydroxymethyl-BA (7-CH2OH-BA), 12-hydroxymethyl-BA (12-CH2OH-BA), 7-hydroxymethyl-12-methyl-BA (7-CH2OH-12-MBA), 5-formyl-BA (5-CHO-BA), BA 5,6-cis-dihydrodiol (BA 5,6-cis-diol), 1-hydroxy-3-methylcholanthene (1-OH-3-MC), 1-keto-3-methylcholanthene (1-keto-3-MC), and 3-MC 1,2-diol. The results indicate that upon photoirradiation by UVA at 7 and 21 J/cm2, respectively all these compounds induced lipid peroxidation and exhibited a relationship between the dose of the light and the level of lipid peroxidation induced. To determine whether or not photoirradiation of these compounds by UVA light produces ROS, an ESR spin-trap technique was employed to provide direct evidence. Photoirradiation of 3-keto-3-MC by UVA (at 389 nm) in the presence of 2,2,6,6-tetramethylpiperidine (TEMP), a specific probe for singlet oxygen, resulted in the formation of TEMPO, indicating that singlet oxygen was generated. These overall results suggest that UVA photoirradiation of oxygenated BA and 3-methylcholanthrene generates singlet oxygen, one of the reactive oxygen species (ROS), which induce lipid peroxidation. PMID:18441402

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Efficient solutions for low-temperature singlet-oxygen generators

NASA Astrophysics Data System (ADS)

Igoshin, Valerii I.; Karyshev, V. D.; Katulin, V. A.; Kirilin, A. V.; Kisletsov, A. V.; Konnov, S. A.; Kupriyanov, N. L.; Medvedev, A. M.; Nadezhina, T. N.

1989-02-01

Experimental investigations were made of the physicochemical characteristics of the active solutions for a chemical generator in an oxygen-iodine laser. A strong temperature dependence of the viscosity of the solution was observed. The influence of this factor on the operation of the singlet-oxygen generator and the laser is discussed. The cyclic operation of a laser with efficient neutralization of the reagents and the addition of an alkali is simulated. It is shown that hydrogen peroxide may be 50% utilized when the temperature of the solution is no higher than - 30 °C. A method of preparing a solution for an iodine laser with a low freezing point (between - 30 °C and - 40 °C) is developed. It is shown that an aqueous solution of hydrogen peroxide with a concentration of 25-40% is suitable.

Luminescence of Radachlorin Photosensitizer in Aqueous Solution under Excitation at 405 and 660 nm

NASA Astrophysics Data System (ADS)

Beltukova, D. M.; Belik, V. P.; Vasyutinskii, O. S.; Gadzhiev, I. M.; Goncharov, S. E.; Semenova, I. V.

2018-01-01

Entire luminescence spectrum of a commercial photosensitizer Radachlorin in aqueous solution has been recorded under laser excitation at 660 nm and analyzed. The peak of singlet oxygen phosphorescence at 1274 nm has been observed. The results obtained were compared with those recorded with laser excitation at 405 nm and reported earlier. The comparison showed the similarity of relaxation and luminescence processes occurring in both cases. Effective absorption cross sections were determined at each excitation wavelength, it was also shown that the singlet oxygen quantum yield is independent of photosensitizer concentration. The lifetime of the first excited triplet state in Radachlorin was determined. The results obtained can be used for optimization of the conditions of singlet oxygen generation and detection in solutions and biological samples.

Singlet Oxygen Generation Mediated By Silicon Nanocrystal Assemblies

DTIC Science & Technology

2011-01-01

Lattice fringes in Fig.3 d correspond to the (111) atomic planes of Si nanocrystals. Length scales are indicated. Downscaling of the stain etched PSi...intensity of 1W/cm2 in a time scale of a few hours a monolayer of oxygen is formed on the surface of Si nanocrystals. Fig. 8. Infrared absorption...solution. Fig. 10. PL intensity as a function of continuously prolonged etching of Si powder. Inset: PL suppression level (can be scaled as singlet

Non-photochemical production of singlet oxygen via activation of persulfate by carbon nanotubes.

PubMed

Cheng, Xin; Guo, Hongguang; Zhang, Yongli; Wu, Xiao; Liu, Yang

2017-04-15

The reaction between persulfate (PS) and carbon nanotubes (CNTs) for the degradation of 2,4-dichlorophenol (2,4-DCP) was investigated. It was demonstrated that CNTs could efficiently activate PS for the degradation of 2,4-DCP. Results suggested that the neither hydroxyl radical (OH) nor sulfate radical (SO 4 - ) was produced therein. For the first time, the generation of singlet oxygen ( 1 O 2 ) was proved by several methods including electron paramagnetic resonance spectrometry (EPR) and liquid chromatography mass spectrometry measurements. Moreover, the generation of the superoxide radical as a precursor of the singlet oxygen was also confirmed by using certain scavengers and EPR measurement, in which the presence of molecular oxygen was not required as a precursor of 1 O 2 . The efficient generation of 1 O 2 using the PS/CNTs system without any light irradiation can be employed for the selective oxidation of aqueous organic compounds under neutral conditions with the mineralization and toxicity evaluated. A kinetic model was developed to theoretically evaluate the adsorption and oxidation of 2,4-DCP on the CNTs. Accordingly, a catalytic mechanism was proposed involving the formation of a dioxirane intermediate between PS and CNTs, and the subsequent decomposition of this intermediate into 1 O 2 . Copyright © 2017 Elsevier Ltd. All rights reserved.

Photosensitized singlet oxygen luminescence from the protein matrix of Zn-substituted myoglobin.

PubMed

Lepeshkevich, Sergei V; Parkhats, Marina V; Stasheuski, Alexander S; Britikov, Vladimir V; Jarnikova, Ekaterina S; Usanov, Sergey A; Dzhagarov, Boris M

2014-03-13

A nanosecond laser near-infrared spectrometer was used to study singlet oxygen ((1)O2) emission in a protein matrix. Myoglobin in which the intact heme is substituted by Zn-protoporphyrin IX (ZnPP) was employed. Every collision of ground state molecular oxygen with ZnPP in the excited triplet state results in (1)O2 generation within the protein matrix. The quantum yield of (1)O2 generation was found to be equal to 0.9 ± 0.1. On the average, six from every 10 (1)O2 molecules succeed in escaping from the protein matrix into the solvent. A kinetic model for (1)O2 generation within the protein matrix and for a subsequent (1)O2 deactivation was introduced and discussed. Rate constants for radiative and nonradiative (1)O2 deactivation within the protein were determined. The first-order radiative rate constant for (1)O2 deactivation within the protein was found to be 8.1 ± 1.3 times larger than the one in aqueous solutions, indicating the strong influence of the protein matrix on the radiative (1)O2 deactivation. Collisions of singlet oxygen with each protein amino acid and ZnPP were assumed to contribute independently to the observed radiative as well as nonradiative rate constants.

Singlet oxygen signatures are detected independent of light or chloroplasts in response to multiple stresses.

PubMed

Mor, Avishai; Koh, Eugene; Weiner, Lev; Rosenwasser, Shilo; Sibony-Benyamini, Hadas; Fluhr, Robert

2014-05-01

The production of singlet oxygen is typically associated with inefficient dissipation of photosynthetic energy or can arise from light reactions as a result of accumulation of chlorophyll precursors as observed in fluorescent (flu)-like mutants. Such photodynamic production of singlet oxygen is thought to be involved in stress signaling and programmed cell death. Here we show that transcriptomes of multiple stresses, whether from light or dark treatments, were correlated with the transcriptome of the flu mutant. A core gene set of 118 genes, common to singlet oxygen, biotic and abiotic stresses was defined and confirmed to be activated photodynamically by the photosensitizer Rose Bengal. In addition, induction of the core gene set by abiotic and biotic selected stresses was shown to occur in the dark and in nonphotosynthetic tissue. Furthermore, when subjected to various biotic and abiotic stresses in the dark, the singlet oxygen-specific probe Singlet Oxygen Sensor Green detected rapid production of singlet oxygen in the Arabidopsis (Arabidopsis thaliana) root. Subcellular localization of Singlet Oxygen Sensor Green fluorescence showed its accumulation in mitochondria, peroxisomes, and the nucleus, suggesting several compartments as the possible origins or targets for singlet oxygen. Collectively, the results show that singlet oxygen can be produced by multiple stress pathways and can emanate from compartments other than the chloroplast in a light-independent manner. The results imply that the role of singlet oxygen in plant stress regulation and response is more ubiquitous than previously thought.

Singlet Oxygen Signatures Are Detected Independent of Light or Chloroplasts in Response to Multiple Stresses1[C][W

PubMed Central

Mor, Avishai; Koh, Eugene; Weiner, Lev; Rosenwasser, Shilo; Sibony-Benyamini, Hadas; Fluhr, Robert

2014-01-01

The production of singlet oxygen is typically associated with inefficient dissipation of photosynthetic energy or can arise from light reactions as a result of accumulation of chlorophyll precursors as observed in fluorescent (flu)-like mutants. Such photodynamic production of singlet oxygen is thought to be involved in stress signaling and programmed cell death. Here we show that transcriptomes of multiple stresses, whether from light or dark treatments, were correlated with the transcriptome of the flu mutant. A core gene set of 118 genes, common to singlet oxygen, biotic and abiotic stresses was defined and confirmed to be activated photodynamically by the photosensitizer Rose Bengal. In addition, induction of the core gene set by abiotic and biotic selected stresses was shown to occur in the dark and in nonphotosynthetic tissue. Furthermore, when subjected to various biotic and abiotic stresses in the dark, the singlet oxygen-specific probe Singlet Oxygen Sensor Green detected rapid production of singlet oxygen in the Arabidopsis (Arabidopsis thaliana) root. Subcellular localization of Singlet Oxygen Sensor Green fluorescence showed its accumulation in mitochondria, peroxisomes, and the nucleus, suggesting several compartments as the possible origins or targets for singlet oxygen. Collectively, the results show that singlet oxygen can be produced by multiple stress pathways and can emanate from compartments other than the chloroplast in a light-independent manner. The results imply that the role of singlet oxygen in plant stress regulation and response is more ubiquitous than previously thought. PMID:24599491

Donor/acceptor nanoparticle pair-based singlet oxygen channeling homogenous chemiluminescence immunoassay for quantitative determination of bisphenol A.

PubMed

Hou, Changjiang; Zhao, Lixia; Geng, Fanglan; Wang, Dan; Guo, Liang-Hong

2016-12-01

Bisphenol A (BPA) is widely used in consumer products such as plastic bottles and food containers. It has become a ubiquitous environmental contaminant and poses a serious risk to human health. A rapid, sensitive, and high-throughput method for detecting BPA is therefore desirable. Herein, a donor/acceptor nanoparticle pair-based singlet oxygen channeling chemiluminescence homogenous immunoassay is developed for the determination of BPA. The donor nanoparticles were modified with phthalocyanine as a photosensitizer and were then coated with streptavidin. The acceptor nanoparticles were doped with thioxene derivatives and Eu(III) as a chemiluminescence emitter and then coated with anti-BPA antibody. Under light irradiation, oxygen near the donor surface transforms to singlet oxygen ( 1 O 2 ), which migrates to the acceptor and reacts with it, generating luminescence. Because 1 O 2 has a very short lifetime, luminescence is generated only when the donor and acceptor are in close proximity. This occurs when they are brought together by the antigen/antibody and streptavidin/biotin reaction. Based on this singlet oxygen channeling mechanism, a competitive homogenous chemiluminescence immunoassay for BPA was developed on 384 microplates. The assay exhibited linear detection over the range 10-1000 ng/mL and a limit of detection of 2.9 ng/mL. The intra- and inter-assay precisions were both below 5.1 %. The average recoveries of three spiked samples in tap and river water samples were in the range 95.5-121.0 %, in agreement with values obtained using high-performance liquid chromatography. The homogeneous assay is rapid, low cost, sensitive, and allows high-throughput, so is well suited for screening large numbers of environmental samples. Graphical abstract Principle of the singlet oxygen channeling homogenous chemiluminescence competitive immunoassay based on nanoparticle pairs for determination of BPA.

Light-triggered liposomal cargo delivery platform incorporating photosensitizers and gold nanoparticles for enhanced singlet oxygen generation and increased cytotoxicity

NASA Astrophysics Data System (ADS)

Kautzka, Zofia; Clement, Sandhya; Goldys, Ewa M.; Deng, Wei

2018-02-01

We developed light-triggered liposomes incorporating gold nanoparticles and Rose Bengal (RB), a well-known photosensitizer used for photodynamic therapy. Singlet oxygen generated by these liposomes with 532 nm light illumination was characterized by adjusting the molar ratio of lipids and gold nanoparticles while keeping the amount of RB constant. Gold nanoparticles were found to enhance the singlet oxygen generation rate, with a maximum enhancement factor of 1.75 obtained for the molar ratio of HSPC: PE-NH2: gold of 57:5:17 compared with liposomes loaded with RB alone. The experimental results could be explained by the local electric field enhancement caused by gold nanoparticles. We further assessed cellular cytotoxicity of these liposomes by encapsulating an antitumor drug, doxorubicin (Dox); such Dox loaded liposomes were applied to human colorectal cancer cells, HCT116, and exposed to light. Gold-loaded liposomes containing RB and Dox where Dox release was triggered by light were found to exhibit higher cytotoxicity, compared to the liposomes loaded with RB and Dox alone. Our results indicate that gold-loaded liposomes incorporating photosensitizers may have improved therapeutic efficacy in photodynamic therapy and chemotherapy.

Increasing the endogenous NO level causes catalase inactivation and reactivation of intercellular apoptosis signaling specifically in tumor cells.

PubMed

Bauer, Georg

2015-12-01

Tumor cells generate extracellular superoxide anions and are protected against intercellular apoptosis-inducing HOCl- and NO/peroxynitrite signaling through the expression of membrane-associated catalase. This enzyme decomposes H2O2 and thus prevents HOCl synthesis. It efficiently interferes with NO/peroxynitrite signaling through oxidation of NO and decomposition of peroxynitrite. The regulatory potential of catalase at the crosspoint of ROS and RNS chemical biology, as well as its high local concentration on the outside of the cell membrane of tumor cells, establish tight control of intercellular signaling and thus prevent tumor cell apoptosis. Therefore, inhibition of catalase or its inactivation by singlet oxygen reactivate intercellular apoptosis-inducing signaling. Nitric oxide and peroxynitrite are connected with catalase in multiple and meaningful ways, as (i) NO can be oxidated by compound I of catalase, (ii) NO can reversibly inhibit catalase, (iii) peroxynitrite can be decomposed by catalase and (iv) the interaction between peroxynitrite and H2O2 leads to the generation of singlet oxygen that inactivates catalase. Therefore, modulation of the concentration of free NO through addition of arginine, inhibition of arginase, induction of NOS expression or inhibition of NO dioxygenase triggers an autoamplificatory biochemical cascade that is based on initial formation of singlet oxygen, amplification of superoxide anion/H2O2 and NO generation through singlet oxygen dependent stimulation of the FAS receptor and caspase-8. Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling. This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors. The latter aspect is explicitely studied for the interaction between catalase inhibiting acetylsalicylic acid and an NO donor. It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential. Our data open novel approaches for rational tumor therapy based on specific ROS signaling and its control in tumor cells. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Singlet oxygen detection in biological systems: Uses and limitations.

PubMed

Koh, Eugene; Fluhr, Robert

2016-07-02

The study of singlet oxygen in biological systems is challenging in many ways. Singlet oxygen is a relatively unstable ephemeral molecule, and its properties make it highly reactive with many biomolecules, making it difficult to quantify accurately. Several methods have been developed to study this elusive molecule, but most studies thus far have focused on those conditions that produce relatively large amounts of singlet oxygen. However, the need for more sensitive methods is required as one begins to explore the levels of singlet oxygen required in signaling and regulatory processes. Here we discuss the various methods used in the study of singlet oxygen, and outline their uses and limitations.

Synthesis and characterization of near-infrared absorbing water soluble squaraines and study of their photodynamic effects in DLA live cells.

PubMed

Shafeekh, Kulathinte M; Soumya, Mohanannair S; Rahim, Moochikkadavath A; Abraham, Annie; Das, Suresh

2014-01-01

Here, we report the synthesis, photophysical properties and photodynamic effects in DLA live cells of three water soluble squaraine dyes, viz. bisbenzothiazolium squaraine dyes SQMI and SQDI with iodine in one and both benzothiazolium units, respectively, and an unsymmetrical squaraine dye ASQI containing iodinated benzothiazolium and aniline substituents. The diiodinated SQDI showed an anomalous trend in both fluorescence and triplet quantum yields over the monoiodinated SQMI, with SQDI showing higher fluorescence and lower triplet quantum yields compared to SQMI. Nanosecond laser flash photolysis of SQDI and SQMI indicated the formation of triplet excited states with quantum yield of 0.19 and 0.26, respectively. On photoirradiation, both the SQDI and SQMI generate singlet oxygen and it was observed that both dyes undergoing oxidation reactions with the singlet oxygen generated. ASQI which exhibited a lower triplet quantum yield of 0.06 was, however, stable and did not react with the singlet oxygen generated. In vitro cytotoxicity studies of these dyes in DLA live cells were performed using Trypan blue dye exclusion method and it reflect an order of cytotoxicity of SQDI>SQMI>ASQI. Intracellular generation of the ROS was confirmed by dichlorofluorescein assay after the in vitro PDT. © 2014 The American Society of Photobiology.

Phosphoprotein SAK1 is a regulator of acclimation to singlet oxygen in Chlamydomonas reinhardtii.

PubMed

Wakao, Setsuko; Chin, Brian L; Ledford, Heidi K; Dent, Rachel M; Casero, David; Pellegrini, Matteo; Merchant, Sabeeha S; Niyogi, Krishna K

2014-05-23

Singlet oxygen is a highly toxic and inevitable byproduct of oxygenic photosynthesis. The unicellular green alga Chlamydomonas reinhardtii is capable of acclimating specifically to singlet oxygen stress, but the retrograde signaling pathway from the chloroplast to the nucleus mediating this response is unknown. Here we describe a mutant, singlet oxygen acclimation knocked-out 1 (sak1), that lacks the acclimation response to singlet oxygen. Analysis of genome-wide changes in RNA abundance during acclimation to singlet oxygen revealed that SAK1 is a key regulator of the gene expression response during acclimation. The SAK1 gene encodes an uncharacterized protein with a domain conserved among chlorophytes and present in some bZIP transcription factors. The SAK1 protein is located in the cytosol, and it is induced and phosphorylated upon exposure to singlet oxygen, suggesting that it is a critical intermediate component of the retrograde signal transduction pathway leading to singlet oxygen acclimation.DOI: http://dx.doi.org/10.7554/eLife.02286.001. Copyright © 2014, Wakao et al.

Singlet-Oxygen Generation in Alkaline Periodate Solution.

PubMed

Bokare, Alok D; Choi, Wonyong

2015-12-15

A nonphotochemical generation of singlet oxygen ((1)O2) using potassium periodate (KIO4) in alkaline condition (pH > 8) was investigated for selective oxidation of aqueous organic pollutants. The generation of (1)O2 was initiated by the spontaneous reaction between IO4(-) and hydroxyl ions, along with a stoichiometric conversion of IO4(-) to iodate (IO3(-)). The reactivity of in-situ-generated (1)O2 was monitored by using furfuryl alcohol (FFA) as a model substrate. The formation of (1)O2 in the KIO4/KOH system was experimentally confirmed using electron spin resonance (ESR) measurements in corroboration with quenching studies using azide as a selective (1)O2 scavenger. The reaction in the KIO4/KOH solution in both oxic and anoxic conditions initiated the generation of superoxide ion as a precursor of the singlet oxygen (confirmed by using superoxide scavengers), and the presence of molecular oxygen was not required as a precursor of (1)O2. Although hydrogen peroxide had no direct influence on the FFA oxidation process, the presence of natural organic matter, such as humic and fulvic acids, enhanced the oxidation efficiency. Using the oxidation of simple organic diols as model compounds, the enhanced (1)O2 formation is attributed to periodate-mediated oxidation of vicinal hydroxyl groups present in humic and fulvic constituent moieties. The efficient and simple generation of (1)O2 using the KIO4/KOH system without any light irradiation can be employed for the selective oxidation of aqueous organic compounds under neutral and near-alkaline conditions.

Singlet oxygen detection in biological systems: Uses and limitations

PubMed Central

Koh, Eugene; Fluhr, Robert

2016-01-01

ABSTRACT The study of singlet oxygen in biological systems is challenging in many ways. Singlet oxygen is a relatively unstable ephemeral molecule, and its properties make it highly reactive with many biomolecules, making it difficult to quantify accurately. Several methods have been developed to study this elusive molecule, but most studies thus far have focused on those conditions that produce relatively large amounts of singlet oxygen. However, the need for more sensitive methods is required as one begins to explore the levels of singlet oxygen required in signaling and regulatory processes. Here we discuss the various methods used in the study of singlet oxygen, and outline their uses and limitations. PMID:27231787

In situ H(+)-mediated formation of singlet oxygen from NaBiO3 for oxidative degradation of bisphenol A without light irradiation: Efficiency, kinetics, and mechanism.

PubMed

Ding, Yaobin; Xia, Xiangli; Ruan, Yufeng; Tang, Heqing

2015-12-01

Bisphenol A (BPA) is a ubiquitous environmental contaminant with endocrine disruption potential. This study explored the efficiency, kinetics, and mechanism of BPA removal from weakly acidic solutions by using NaBiO3 as a source of singlet oxygen. It was observed that the use of NaBiO3 (1gL(-1)) could eliminate almost all (more than 97%) of the added BPA (0.1mmolL(-1)) in solutions at pH 5.0 in 60min. The degradation of BPA followed pseudo-first-order kinetics over the pH range from 3 to 9, and the pseudo-first-order rate constant (k) was dependent on pH, NaBiO3 concentration and the coexisting compounds. As solution pH was decreased from 9 to 3 or NaBiO3 concentration was increased from 0.5 to 2gL(-1), the k value was increased logarithmically. Humic acid and Fe(3+) showed little effect on the BPA removal, but Mn(2+) exhibited exceptionally enhancing effect on the degradation of BPA. The involved reactive species were identified as singlet oxygen by using radical scavenger probes and ESR measurement, and the generated singlet oxygen was confirmed to be generated from the decomposition of NaBiO3 mediated by H(+) ions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lycopene inhibits the isomerization of β-carotene during quenching of singlet oxygen and free radicals.

PubMed

Heymann, Thomas; Heinz, Philipp; Glomb, Marcus A

2015-04-01

The present study aimed to investigate the influence of singlet oxygen and radical species on the isomerization of carotenoids. On the one hand, lycopene and β-carotene standards were incubated with 1,4-dimethylnaphthalene-1,4-endoperoxide that produced singlet oxygen in situ. (13Z)- and (15Z)-β-carotene were preferentially generated at low concentrations of singlet oxygen, while high concentrations resulted in formation of (9Z)-β-carotene. The addition of different concentrations of lycopene led to the same isomerization progress of β-carotene, but resulted in a decreased formation of (9Z)-β-carotene and retarded degradation of (all-E)-β-carotene. On the other hand, isomerization of β-carotene and lycopene was induced by ABTS-radicals, too. As expected from the literature, chemical quenching was observed especially for lycopene, while physical quenching was preferred for β-carotene. Mixtures of β-carotene and lycopene resulted in a different isomerization progress compared to the separate β-carotene model. As long as lycopene was present, almost no isomerization of β-carotene was triggered; after that, strong formation of (13Z)-, (9Z)-, and (15Z)-β-carotene was initiated. In summary, lycopene protected β-carotene against isomerization during reactions with singlet oxygen and radicals. These findings can explain the pattern of carotenoid isomers analyzed in fruits and vegetables, where lycopene containing samples showed higher (all-E)/(9Z)-β-carotene ratios, and also in in vivo samples such as human blood plasma.

Measurement of antiphotooxidative properties of isoquinoline alkaloids using transient thermal lens spectroscopy

NASA Astrophysics Data System (ADS)

Hung, J.; Castillo, J.; Laboren, I.; Rodríguez, M.; Hassegawa, M.

2005-11-01

The antiphotooxidative properties of boldine and chloride berberine were studied by time-resolved thermal lensing technique. These compounds belong to isoquinoline alkaloids possessing interesting biological activity (e.g. antibacterial, antimalarial, antitumor). Antiphotooxidative properties of the alkaloids were studied by mechanism of energy transference between powerful oxidizing agents such as singlet oxygen. Singlet oxygen was produced by energy transfer from chlorophyll-sensitized photooxidation of oil by exposure of high light intensities like laser. The lifetimes of singlet oxygen in dimethylsulfoxide, methanol and water were determined to confirm the assignment of the singlet molecular oxygen O II (1Δ g) in the experiments. In order to understand the effect of the alkaloids on active oxygen species, we carried out in detail an analysis of the thermal lensing signal. It was shown that the alkaloids can act as quenchers of singlet oxygen. To demonstrate the ability of the alkaloids to act efficient singlet oxygen acceptors, we have measured the fluorescence spectra of the studied alkaloids in the presence and in the absence of singlet oxygen. The antiphotooxidative activity of boldine and chloride berberine can be explained by the ability to quench singlet oxygen.

Bovine Serum Albulmin Protein-Templated Silver Nanocluster (BSA-Ag13 ): An Effective Singlet Oxygen Generator for Photodynamic Cancer Therapy.

PubMed

Yu, Yong; Geng, Junlong; Ong, Edward Yong Xi; Chellappan, Vijila; Tan, Yen Nee

2016-10-01

This paper reports a novel synthesis approach of bovine serum albumin (BSA) protein-templated ultrasmall (<2 nm) Ag nanocluster (NC) with strong singlet oxygen generation capacity for photodynamic therapy (PDT). An atomically precise BSA-Ag 13 NC (i.e., 13 Ag atoms per cluster) is successfully synthesized for the first time by using NaOH-dissolved NaBH 4 solution as the controlling reducing agent. The ubiquitous size of BSA-Ag 13 NC results in unique behaviors of its photoexcited states as characterized by the ultrafast laser spectroscopy using time-correlated single photon counting and transient absorption techniques. In particular, triply excited states can be largely present in the excited BSA-Ag 13 NC and readily sensitized molecular oxygen to produce singlet oxygen ( 1 O 2 ) with a high quantum efficiency (≈1.26 using Rose Bengal as a standard). This value is much higher than its Au analogue (i.e., ≈0.07 for BSA-Au 25 NC) and the commonly available photosensitizers. Due to the good cellular uptake and inherent biocompatibility imparted by the surface protein, BSA-Ag 13 NC can be applied as an effective PDT agent in generating 1 O 2 to kill cancer cell as demonstrated in this study. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Note: Measuring instrument of singlet oxygen quantum yield in photodynamic effects

NASA Astrophysics Data System (ADS)

Li, Zhongwei; Zhang, Pengwei; Zang, Lixin; Qin, Feng; Zhang, Zhiguo; Zhang, Hongli

2017-06-01

Using diphenylisobenzofuran (C20H14O) as a singlet oxygen (1O2) reporter, a comparison method, which can be used to measure the singlet oxygen quantum yield (ΦΔ) of the photosensitizer quantitatively, is presented in this paper. Based on this method, an automatic measuring instrument of singlet oxygen quantum yield is developed. The singlet oxygen quantum yield of the photosensitizer hermimether and aloe-emodin is measured. It is found that the measuring results are identical to the existing ones, which verifies the validity of the measuring instrument.

Photodynamic activity of pyropheophorbide methyl ester and pyropheophorbide a in dimethylformamide solution.

PubMed

Al-Omari, Saleh; Ali, Ahmad

2009-03-01

Comparative spectroscopic study including the photosensitizers of pyropheophorbide methyl ester (PPME) and pyropheophorbide a (PPa) was performed to study their photodynamic activity. The investigated photosensitizers in a homogeneous system of dimethylformamide (DMF) are not photostable upon irradiation. The photobleaching efficiency of PPa is higher than that of PPME. Combining these results with the data obtained by measuring the singlet oxygen quantum yield and the hydroxyl group generation, it was revealed that the photobleaching efficiency could be correlated with the singlet oxygen quantum yield and the hydroxyl group production of the photosensitizer.

Light-triggered liposomal cargo delivery platform incorporating photosensitizers and gold nanoparticles for enhanced singlet oxygen generation and increased cytotoxicity.

PubMed

Kautzka, Zofia; Clement, Sandhya; Goldys, Ewa M; Deng, Wei

2017-01-01

We developed light-triggered liposomes incorporating 3-5 nm hydrophobic gold nanoparticles and Rose Bengal (RB), a well-known photosensitizer used for photodynamic therapy. Singlet oxygen generated by these liposomes with 532 nm light illumination was characterized for varying the molar ratio of lipids and gold nanoparticles while keeping the amount of RB constant. Gold nanoparticles were found to enhance the singlet oxygen generation rate, with a maximum enhancement factor of 1.75 obtained for the molar ratio of hydrogenated soy l-α-phosphatidylcholine:1,2-dioleoyl- sn -glycero-3-phosphoethanolamine- N -(hexanoylamine):gold of 57:5:17 compared with liposomes loaded with RB alone. The experimental results could be explained by the local electric field enhancement caused by gold nanoparticles. We further assessed cellular cytotoxicity of gold-loaded liposomes by encapsulating an antitumor drug, doxorubicin (Dox); such Dox-loaded liposomes were applied to human colorectal cancer cells (HCT116) and exposed to light. Gold-loaded liposomes containing RB and Dox where Dox release was triggered by light were found to exhibit higher cytotoxicity compared with the liposomes loaded with RB and Dox alone. Our results indicate that gold-loaded liposomes incorporating photosensitizers may serve as improved agents in photodynamic therapy and chemotherapy.

Light-triggered liposomal cargo delivery platform incorporating photosensitizers and gold nanoparticles for enhanced singlet oxygen generation and increased cytotoxicity

PubMed Central

Kautzka, Zofia; Clement, Sandhya; Goldys, Ewa M; Deng, Wei

2017-01-01

We developed light-triggered liposomes incorporating 3–5 nm hydrophobic gold nanoparticles and Rose Bengal (RB), a well-known photosensitizer used for photodynamic therapy. Singlet oxygen generated by these liposomes with 532 nm light illumination was characterized for varying the molar ratio of lipids and gold nanoparticles while keeping the amount of RB constant. Gold nanoparticles were found to enhance the singlet oxygen generation rate, with a maximum enhancement factor of 1.75 obtained for the molar ratio of hydrogenated soy l-α-phosphatidylcholine:1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(hexanoylamine):gold of 57:5:17 compared with liposomes loaded with RB alone. The experimental results could be explained by the local electric field enhancement caused by gold nanoparticles. We further assessed cellular cytotoxicity of gold-loaded liposomes by encapsulating an antitumor drug, doxorubicin (Dox); such Dox-loaded liposomes were applied to human colorectal cancer cells (HCT116) and exposed to light. Gold-loaded liposomes containing RB and Dox where Dox release was triggered by light were found to exhibit higher cytotoxicity compared with the liposomes loaded with RB and Dox alone. Our results indicate that gold-loaded liposomes incorporating photosensitizers may serve as improved agents in photodynamic therapy and chemotherapy. PMID:28203076

Phosphorescence Kinetics of Singlet Oxygen Produced by Photosensitization in Spherical Nanoparticles. Part I. Theory.

PubMed

Hovan, Andrej; Datta, Shubhashis; Kruglik, Sergei G; Jancura, Daniel; Miskovsky, Pavol; Bánó, Gregor

2018-05-24

The singlet oxygen produced by energy transfer between an excited photosensitizer (pts) and ground-state oxygen molecules plays a key role in photodynamic therapy. Different nanocarrier systems are extensively studied to promote targeted pts delivery in a host body. The phosphorescence kinetics of the singlet oxygen produced by the short laser pulse photosensitization of pts inside nanoparticles is influenced by singlet oxygen diffusion from the particles to the surrounding medium. Two theoretical models are presented in this work: a more complex numerical one and a simple analytical one. Both the models predict the time course of singlet oxygen concentration inside and outside of the spherical particles following short-pulse excitation of pts. On the basis of the comparison of the numerical and analytical results, a semiempirical analytical formula is derived to calculate the characteristic diffusion time of singlet oxygen from the nanoparticles to the surrounding solvent. The phosphorescence intensity of singlet oxygen produced in pts-loaded nanocarrier systems can be calculated as a linear combination of the two concentrations (inside and outside the particles), taking the different phosphorescence emission rate constants into account.

Phthalocyanines functionalized with 2-methyl-5-nitro-1H-imidazolylethoxy and 1,4,7-trioxanonyl moieties and the effect of metronidazole substitution on photocytotoxicity.

PubMed

Wierzchowski, Marcin; Sobotta, Lukasz; Skupin-Mrugalska, Paulina; Kruk, Justyna; Jusiak, Weronika; Yee, Michael; Konopka, Krystyna; Düzgüneş, Nejat; Tykarska, Ewa; Gdaniec, Maria; Mielcarek, Jadwiga; Goslinski, Tomasz

2013-10-01

Four novel magnesium(II) and zinc(II) phthalocyanines bearing 1,4,7-trioxanonyl, polyether and/or (2-methyl-5-nitro-1H-imidazol-1-yl)ethoxy, heterocyclic substituents at their non-peripheral positions were synthesized and assessed in terms of physicochemical and biological properties. Magnesium phthalocyanine derivatives bearing polyether substituents (Pc-1), a mixed system of polyether and heterocyclic substituents (Pc-3), and four heterocyclic substituents (Pc-4), respectively, were synthesized following the Linstead macrocyclization reaction procedure. Zinc phthalocyanine (Pc-2) bearing polyether substituents at non-peripheral positions was synthesized following the procedure in n-pentanol with the zinc acetate, and DBU. Novel phthalocyanines were purified by flash column chromatography and characterized using NMR, MS, UV-Vis and HPLC. Moreover, two precursors in macrocyclization reaction phthalonitriles were characterized using X-ray. Photophysical properties of the novel macrocycles were evaluated, including UV-Vis spectra analysis and aggregation study. All macrocycles subjected to singlet oxygen generation and the oxidation rate constant measurements exhibited lower quantum yields of singlet oxygen generation in DMSO than in DMF. In addition, the Pc-2 molecule was found to be the most efficient singlet oxygen generator from the group of macrocycles studied. The photocytotoxicity evaluated on the human oral squamous cell carcinoma cell line, HSC-3, for Pc-3 was significantly higher than that for Pc-1, Pc-2, and Pc-4. Interestingly, Pc-3 was found to be the most active macrocycle in vitro although its ability to generate singlet oxygen was significantly lower than those of Pc-1 and Pc-2. However, attempts to encapsulate phthalocyanines Pc-1-Pc-3 in liposomal membranes were unsuccessful. The phthalocyanine-nitroimidazole conjugate, Pc-4 was encapsulated in phosphatidylglycerol:phosphatidylcholine unilamellar liposomes and subjected to photocytotoxicity study. © 2013.

New singlet oxygen donors based on naphthalenes: synthesis, physical chemical data, and improved stability.

PubMed

Klaper, Matthias; Linker, Torsten

2015-06-01

Singlet oxygen donors are of current interest for medical applications, but suffer from a short half-life leading to low singlet oxygen yields and problems with storage. We have synthesized more than 25 new singlet oxygen donors based on differently substituted naphthalenes in only a few steps. The influence of functional groups on the reaction rate of the photooxygenations, thermolysis, half-life, and singlet oxygen yield has been thoroughly studied. We determined various thermodynamic data and compared them with density functional calculations. Interestingly, remarkable stabilities of functional groups during the photooxygenations and stabilizing effects for some endoperoxides during the thermolysis have been found. Furthermore, we give evidence for a partly concerted and partly stepwise thermolysis mechanism leading to singlet and triplet oxygen, respectively. Our results might be interesting for "dark oxygenations" and future applications in medicine. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optically (solar) pumped oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Danilov, O. B.; Zhevlakov, A. P.; Yur'ev, M. S.

2014-07-01

We present the results of theoretical and experimental studies demonstrating the possibility of developing an oxygen-iodine laser (OIL) with direct optical pumping of molecular oxygen involving inter-molecular interaction with charge transfer from donor molecule (buffer gas) to acceptor molecule (oxygen). This interaction lifts degeneracy of the lower energy states of molecular oxygen and increases its absorption cross section in the visible spectral region and the UV Herzberg band, where high quantum yield of singlet oxygen is achieved (QY ˜ 1 and QY ˜ 2, respectively) at the same time. A pulse-periodic optical pump sources with pulse energy of ˜50 kJ, pulse duration of ˜25 μs, and repetition rate of ˜10 Hz, which are synchronized with the mechanism of singlet oxygen generation, are developed. This allows implementation of a pulse-periodic oxygen-iodine laser with an efficiency of ˜25%, optical efficiency of ˜40%, and parameter L/ T ˜ 1/1.5, where T is the thermal energy released in the laser active medium upon generation of energy L. It is demonstrated that, under direct solar pumping of molecular oxygen, the efficiency parameter of the OIL can reach L/ T ˜ 1/0.8 in a wide range of scaling factors.

Phosphorescence Kinetics of Singlet Oxygen Produced by Photosensitization in Spherical Nanoparticles. Part II. The Case of Hypericin-Loaded Low-Density Lipoprotein Particles.

PubMed

Datta, Shubhashis; Hovan, Andrej; Jutková, Annamária; Kruglik, Sergei G; Jancura, Daniel; Miskovsky, Pavol; Bánó, Gregor

2018-05-24

The phosphorescence kinetics of singlet oxygen produced by photosensitized hypericin (Hyp) molecules inside low-density lipoprotein (LDL) particles was studied experimentally and by means of numerical and analytical modeling. The phosphorescence signal was measured after short laser pulse irradiation of aqueous Hyp/LDL solutions. The Hyp triplet state lifetime determined by a laser flash-photolysis measurement was 5.3 × 10 -6 s. The numerical and the analytical model described in part I of the present work (DOI: 10.1021/acs.jpcb.8b00658) were used to analyze the observed phosphorescence kinetics of singlet oxygen. It was shown that singlet oxygen diffuses out of LDL particles on a time scale shorter than 0.1 μs. The total (integrated) concentration of singlet oxygen inside LDL is more than an order of magnitude smaller than the total singlet oxygen concentration in the solvent. The time course of singlet oxygen concentrations inside and outside the particles was calculated using simplified representations of the LDL internal structure. The experimental phosphorescence data were fitted by a linear combination of these concentrations using the emission factor E (the ratio of the radiative singlet oxygen depopulation rate constants inside and outside LDL) as a fitting parameter. The emission factor was determined to be E = 6.7 ± 2.5. Control measurements were carried out by adding sodium azide, a strong singlet oxygen quencher, to the solution.

O2(a1Δ) Quenching In The O/O2/O3 System

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-10-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ)+O+M→2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ) quenching were followed by observing the 1268 nm fluorescence of the O2a1Δ-X3∑ transition. Fast quenching of O2(a1Δ) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

Mimicking the photosynthetic triplet energy-transfer relay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gust, D.; Moore, T.A.; Moore, A.L.

1993-06-30

In the reaction centers of photosynthetic organisms, chlorophyll triplet states are sometimes formed by recombination of charge-separated intermediates. These triplets are excellent sensitizers for singlet oxygen formation. Carotenoid polyenes can provide photoprotection from singlet oxygen generation by rapidly quenching chlorophyll triplet states via triplet-triplet energy transfer. Because in bacteria the reaction center carotenoid is not located adjacent to the bacteriochlorophyll special pair, which is the origin of the charge separation, it has been postulated that quenching may occur via a triplet relay involving an intermediate chlorophyll monomer. We now report the synthesis and spectroscopic study of a covalently linked carotenoidmore » (C)-porphyrin (P)-pyropheophorbide (Ppd) triad molecule which mimics this triplet relay. The pyropheophorbide singlet-state C-P-[sup 1]Ppd (generated by direct excitation or energy transfer from the attached porphyrin) undergoes intersystem crossing to the triplet C-P-[sup 3]Ppd. In oxygen-free solutions, this triplet decays to [sup 3]C-p-Ppd through a triplet-transfer relay involving an intermediate C-[sup 3]P-Ppd species. In aerated solutions, quenching of C-P-[sup 3]Ppd by the attached carotenoid competes with singlet oxygen sensitization and thus provides a degree of photoprotection. In a similar traid containing a zinc porphyrin moiety, triplet transfer is slow due to the higher energy of the C-[sup 3]P[sub Zn]-Ppd intermediate, and photoprotection via the relay is nonexistent. The triplet relay ceases to function at low temperatures in both the natural and biomimetic cases due to the endergonicity of the first step. 37 refs., 6 figs., 1 tab.« less

Light- and singlet oxygen-mediated antifungal activity of phenylphenalenone phytoalexins.

PubMed

Lazzaro, Alejandra; Corominas, Montserrat; Martí, Cristina; Flors, Cristina; Izquierdo, Laura R; Grillo, Teresa A; Luis, Javier G; Nonell, Santi

2004-07-01

The light-induced singlet oxygen production and antifungal activity of phenylphenalenone phytoalexins isolated from infected banana plants (Musa acuminata) are reported. Upon absorption of light energy all studied phenylphenalenones sensitise the production of singlet oxygen in polar and non-polar media. Antifungal activity of these compounds towards Fusarium oxysporum is enhanced in the presence of light. These results, together with the correlation of IC50 values under illumination with the quantum yield of singlet oxygen production and the enhancing effect of D2O on the antifungal activity, suggest the intermediacy of singlet oxygen produced by electronic excitation of the phenylphenalenone phytoalexins.

Photophysical properties of fullerene-dendron-pyropheophorbide supramolecules

NASA Astrophysics Data System (ADS)

Ermilov, E. A.; Al-Omari, S.; Helmreich, M.; Jux, N.; Hirsch, A.; Röder, B.

2004-05-01

Two novel monofullerene-bis(pyropheophorbide a) complexes were synthesized and their photophysical properties were studied by using both steady-state and time-resolved techniques. It was revealed that in the pyropheophorbide a (pyroPheo)-C 60 molecular system (FP1) strong quenching of the first excited singlet state of the pyroPheo and, as result, dramatically decreasing of photosensitized singlet oxygen generation occurs by efficient photoinduced electron transfer to the fullerene molecule with a rate constant of 2.5 × 10 9 s -1. In contrast, the fullerene hexaadduct-bis(pyroPheo) system (FHP1), which possesses five diethyl malonate addends in the remaining octahedral positions, shows a high singlet oxygen quantum yield which is due to the reduced fullerene chromophore which is not a good electron acceptor anymore.

Characterization of photoactivated singlet oxygen damage in single-molecule optical trap experiments.

PubMed

Landry, Markita P; McCall, Patrick M; Qi, Zhi; Chemla, Yann R

2009-10-21

Optical traps or "tweezers" use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments-the most common biological application of optical tweezers-and may guide the development of more robust experimental protocols.

Characterization of Photoactivated Singlet Oxygen Damage in Single-Molecule Optical Trap Experiments

PubMed Central

Landry, Markita P.; McCall, Patrick M.; Qi, Zhi; Chemla, Yann R.

2009-01-01

Abstract Optical traps or “tweezers” use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments—the most common biological application of optical tweezers—and may guide the development of more robust experimental protocols. PMID:19843445

Continuous process for singlet oxygenation of hydrophobic substrates in microemulsion using a pervaporation membrane.

PubMed

Caron, Laurent; Nardello, Véronique; Mugge, José; Hoving, Erik; Alsters, Paul L; Aubry, Jean-Marie

2005-02-15

Chemically generated singlet oxygen (1O2, 1Deltag) is able to oxidize a great deal of hydrophobic substrates from molybdate-catalyzed hydrogen peroxide decomposition, provided a suitable reaction medium such as a microemulsion system is used. However, high substrate concentrations or poorly reactive organics require large amounts of H2O2 that generate high amounts of water and thus destabilize the system. We report results obtained on combining dark singlet oxygenation of hydrophobic substrates in microemulsions with a pervaporation membrane process. To avoid composition alterations after addition of H2O2 during the peroxidation, the reaction mixture circulates through a ceramic membrane module that enables a partial and selective dewatering of the microemulsion. Optimization phase diagrams of sodium molybdate/water/alcohol/anionic surfactant/organic solvent have been elaborated to maximize the catalyst concentration and therefore the reaction rate. The membrane selectivity towards the mixture constituents has been investigated showing that a high retention is observed for the catalyst, for organic solvents and hydrophobic substrates, but not for n-propanol (cosurfactant) and water. The efficiency of such a process is illustrated with the peroxidation of a poorly reactive substrate, viz., beta-pinene.

Two-dimensional singlet oxygen imaging with its near-infrared luminescence during photosensitization

PubMed Central

Hu, Bolin; Zeng, Nan; Liu, Zhiyi; Ji, Yanhong; Xie, Weidong; Peng, Qing; Zhou, Yong; He, Yonghong; Ma, Hui

2011-01-01

Photodynamic therapy is a promising cancer treatment that involves activation of photosensitizer by visible light to create singlet oxygen. This highly reactive oxygen species is believed to induce cell death and tissue destruction in PDT. Our approach used a near-infrared area CCD with high quantum efficiency to detect singlet oxygen by its 1270-nm luminescence. Two-dimensional singlet oxygen images with its near-infrared luminescence during photosensitization could be obtained with a CCD integration time of 1 s, without scanning. Thus this system can produce singlet oxygen luminescence images faster and achieve more accurate measurements in comparison to raster-scanning methods. The experimental data show a linear relationship between the singlet oxygen luminescence intensity and sample concentration. This method provides a detection sensitivity of 0.0181 μg/ml (benzoporphyrin derivative monoacid ring A dissolved in ethanol) and a spatial resolution better than 50 μm. A pilot study was conducted on a total of six female Kunming mice. The results from this study demonstrate the system's potential for in vivo measurements. Further experiments were carried out on two tumor-bearing nude mice. Singlet oxygen luminescence images were acquired from the tumor-bearing nude mouse with intravenous injection of BPD-MA, and the experimental results showed real-time singlet oxygen signal depletion as a function of the light exposure. PMID:21280909

Lanthanum(III)-catalyzed disproportionation of hydrogen peroxide: a heterogeneous generator of singlet molecular oxygen-1O2 (1Deltag)-in near-neutral aqueous and organic media for peroxidation of electron-rich substrates.

PubMed

Nardello, Véronique; Barbillat, Jacques; Marko, Jean; Witte, Peter T; Alsters, Paul L; Aubry, Jean-Marie

2003-01-20

The decomposition of hydrogen peroxide into singlet molecular oxygen-(1)O(2) ((1)Delta(g))-in the presence of lanthanum(iii) salts was studied by monitoring its characteristic IR luminescence at 1270 nm. The process was found to be heterogeneously catalyzed by La(III), provided that the heterogeneous catalyst is generated in situ. The yield of (1)O(2) generation was assessed as 45+/-5 % both in water and in methanol. The pH-dependence on the rate of (1)O(2) generation corresponds to a bell-shaped curve from pH 4.5 to 13 with a maximum around pH 8. The study of the influence of H(2)O(2) showed that the formation of (1)O(2) begins as soon as one equivalent of H(2)O(2) is introduced. It then increases drastically up to two equivalents and more smoothly above. Unlike all other metal salt catalyst systems known to date for H(2)O(2) disproportionation, this chemical source of (1)O(2) is able to generate (1)O(2) not only in basic media, but also under neutral and slightly acidic conditions. In addition, this La-based catalyst system has a very low tendency to induce unwanted oxygenating side reactions, such as epoxidation of alkenes. These two characteristics of the heterogeneous lanthanum catalyst system allow non-photochemical (i.e., "dark") singlet oxygenation of substrate classes that cannot be peroxidized successfully with conventional molybdate catalysts, such as allylic alcohols and alkenyl amines.

Photo-excitation of carotenoids causes cytotoxicity via singlet oxygen production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshii, Hiroshi, E-mail: yoshii@nirs.go.jp; Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui 910-1193; Yoshii, Yukie, E-mail: yukiey@nirs.go.jp

Highlights: Black-Right-Pointing-Pointer Some photo-excited carotenoids have photosensitizing ability. Black-Right-Pointing-Pointer They are able to produce ROS. Black-Right-Pointing-Pointer Photo-excited fucoxanthin can produce singlet oxygen through energy transfer. -- Abstract: Carotenoids, natural pigments widely distributed in algae and plants, have a conjugated double bond system. Their excitation energies are correlated with conjugation length. We hypothesized that carotenoids whose energy states are above the singlet excited state of oxygen (singlet oxygen) would possess photosensitizing properties. Here, we demonstrated that human skin melanoma (A375) cells are damaged through the photo-excitation of several carotenoids (neoxanthin, fucoxanthin and siphonaxanthin). In contrast, photo-excitation of carotenoids that possess energymore » states below that of singlet oxygen, such as {beta}-carotene, lutein, loroxanthin and violaxanthin, did not enhance cell death. Production of reactive oxygen species (ROS) by photo-excited fucoxanthin or neoxanthin was confirmed using a reporter assay for ROS production with HeLa Hyper cells, which express a fluorescent indicator protein for intracellular ROS. Fucoxanthin and neoxanthin also showed high cellular penetration and retention. Electron spin resonance spectra using 2,2,6,6-tetramethil-4-piperidone as a singlet oxygen trapping agent demonstrated that singlet oxygen was produced via energy transfer from photo-excited fucoxanthin to oxygen molecules. These results suggest that carotenoids such as fucoxanthin, which are capable of singlet oxygen production through photo-excitation and show good penetration and retention in target cells, are useful as photosensitizers in photodynamic therapy for skin disease.« less

Quenching of I(2P1/2) by O3 and O(3P).

PubMed

Azyazov, Valeriy N; Antonov, Ivan O; Heaven, Michael C

2007-04-26

Oxygen-iodine lasers that utilize electrical or microwave discharges to produce singlet oxygen are currently being developed. The discharge generators differ from conventional chemical singlet oxygen generators in that they produce significant amounts of atomic oxygen. Post-discharge chemistry includes channels that lead to the formation of ozone. Consequently, removal of I(2P1/2) by O atoms and O3 may impact the efficiency of discharge driven iodine lasers. In the present study, we have measured the rate constants for quenching of I(2P1/2) by O(3P) atoms and O3 using pulsed laser photolysis techniques. The rate constant for quenching by O3, (1.8 +/- 0.4) x 10(-12) cm3 s-1, was found to be a factor of 5 smaller than the literature value. The rate constant for quenching by O(3P) was (1.2 +/- 0.2) x 10(-11) cm3 s-1.

Rapid assessment of singlet oxygen-induced plasma lipid oxidation and its inhibition by antioxidants with diphenyl-1-pyrenylphosphine (DPPP).

PubMed

Morita, Mayuko; Naito, Yuji; Yoshikawa, Toshikazu; Niki, Etsuo

2016-01-01

Recent studies suggesting the involvement of singlet oxygen in the pathogenesis of multiple diseases have attracted renewed attention to lipid oxidation mediated by singlet oxygen. Although the rate constants for singlet oxygen quenching by antioxidants have been measured extensively, the inhibition of lipid oxidation mediated by singlet oxygen has received relatively less attention, partly because a convenient method for measuring the rate of lipid oxidation is not available. The objective of this study was to develop a convenient method to measure plasma lipid oxidation mediated by singlet oxygen which may be applied to a rapid assessment of the antioxidant capacity to inhibit this oxidation using a conventional microplate reader. Singlet oxygen was produced from naphthalene endoperoxide, and lipid hydroperoxide production was followed by using diphenyl-1-pyrenylphosphine (DPPP). Non-fluorescent DPPP reacts stoichiometrically with lipid hydroperoxides to give highly fluorescent DPPP oxide. It was found that plasma oxidation by singlet oxygen increased the fluorescence intensity of DPPP oxide, which was suppressed by antioxidants. Fucoxanthin suppressed the oxidation more efficiently than β-carotene and α-tocopherol, while ascorbic acid and Trolox were not effective. The present method may be useful for monitoring lipid oxidation and also for rapid screening of the capacity of dietary antioxidants and natural products to inhibit lipid oxidation in a biologically relevant system.

Relativistic potential energy surfaces of initial oxidations of Si(100) by atomic oxygen: The importance of surface dimer triplet state

NASA Astrophysics Data System (ADS)

Kim, Tae-Rae; Shin, Seokmin; Choi, Cheol Ho

2012-06-01

The non-relativistic and relativistic potential energy surfaces (PESs) of the symmetric and asymmetric reaction paths of Si(100)-2×1 oxidations by atomic oxygen were theoretically explored. Although only the singlet PES turned out to exist as a major channel leading to "on-dimer" product, both the singlet and triplet PESs leading to "on-top" products are attractive. The singlet PESs leading to the two surface products were found to be the singlet combinations (open-shell singlet) of the low-lying triplet state of surface silicon dimer and the ground 3P state of atomic oxygen. The triplet state of the "on-top" product can also be formed by the ground singlet state of the surface silicon dimer and the same 3P oxygen. The attractive singlet PESs leading to the "on-dimer" and "on-top" products made neither the intersystem crossings from triplet to singlet PES nor high energy 1D of atomic oxygen necessary. Rather, the low-lying triplet state of surface silicon dimer plays an important role in the initial oxidations of silicon surface.

The photophysics of monomeric bacteriochlorophylls c and d and their derivatives: properties of the triplet state and singlet oxygen photogeneration and quenching

NASA Technical Reports Server (NTRS)

Krasnovsky, A. A. Jr; Cheng, P.; Blankenship, R. E.; Moore, T. A.; Gust, D.

1993-01-01

Measurements of pigment triplet-triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium-free and farnesyl-free analogs. The energies of the pigment triplet states fell in the range 1.29-1.34 eV. The triplet lifetimes in aerobic solutions were 200-250 ns; they increased to 280 +/- 70 microseconds after nitrogen purging in liquid solutions and to 0.7-2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0-2.5) x 10(9) M-1 s-1, which is close to 1/9 of the rate constant for diffusion-controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were 55-75% in air-saturated solutions. Singlet oxygen quenching by ground-state pigment molecules was observed. Quenching was the most efficient for magnesium-containing pigments, kq = (0.31-1.2) x 10(9) M-1 s-1. It is caused mainly by a physical process of singlet oxygen (1O2) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen.

Roles of reactive oxygen species in UVA-induced oxidation of 5,6-dihydroxyindole-2-carboxylic acid-melanin as studied by differential spectrophotometric method.

PubMed

Ito, Shosuke; Kikuta, Marina; Koike, Shota; Szewczyk, Grzegorz; Sarna, Michal; Zadlo, Andrzej; Sarna, Tadeusz; Wakamatsu, Kazumasa

2016-05-01

Eumelanin photoprotects pigmented tissues from ultraviolet (UV) damage. However, UVA-induced tanning seems to result from the photooxidation of preexisting melanin and does not contribute to photoprotection. We investigated the mechanism of UVA-induced degradation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-melanin taking advantage of its solubility in a neutral buffer and using a differential spectrophotometric method to detect subtle changes in its structure. Our methodology is suitable for examining the effects of various agents that interact with reactive oxygen species (ROS) to determine how ROS is involved in the UVA-induced oxidative modifications. The results show that UVA radiation induces the oxidation of DHICA to indole-5,6-quinone-2-carboxylic acid in eumelanin, which is then cleaved to form a photodegraded, pyrrolic moiety and finally to form free pyrrole-2,3,5-tricarboxylic acid. The possible involvement of superoxide radical and singlet oxygen in the oxidation was suggested. The generation and quenching of singlet oxygen by DHICA-melanin was confirmed by direct measurements of singlet oxygen phosphorescence. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Computational Study of Oxidation of Guanine by Singlet Oxygen (1 Δg ) and Formation of Guanine:Lysine Cross-Links.

PubMed

Thapa, Bishnu; Munk, Barbara H; Burrows, Cynthia J; Schlegel, H Bernhard

2017-04-27

Oxidation of guanine in the presence of lysine can lead to guanine-lysine cross-links. The ratio of the C4, C5 and C8 crosslinks depends on the manner of oxidation. Type II photosensitizers such as Rose Bengal and methylene blue can generate singlet oxygen, which leads to a different ratio of products than oxidation by type I photosensitizers or by one electron oxidants. Modeling reactions of singlet oxygen can be quite challenging. Reactions have been explored using CASSCF, NEVPT2, DFT, CCSD(T), and BD(T) calculations with SMD implicit solvation. The spin contamination in open-shell calculations were corrected by Yamaguchi's approximate spin projection method. The addition of singlet oxygen to guanine to form guanine endo- peroxide proceeds step-wise via a zwitterionic peroxyl intermediate. The subsequent barrier for ring closure is smaller than the initial barrier for singlet oxygen addition. Ring opening of the endoperoxide by protonation at C4-O is followed by loss of a proton from C8 and dehydration to produce 8-oxoG ox . The addition of lysine (modelled by methylamine) or water across the C5=N7 double bond of 8-oxoG ox is followed by acyl migration to form the final spiro products. The barrier for methylamine addition is significantly lower than for water addition and should be the dominant reaction channel. These results are in good agreement with the experimental results for the formation of guanine-lysine cross-links by oxidation by type II photosensitizers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

New singlet oxygen generator for chemical oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Yoshida, S.; Saito, H.; Fujioka, T.; Yamakoshi, H.; Uchiyama, T.

1986-11-01

Experiments have been carried out to investigate a new method for generating O2(1Delta) with long-time operation of an efficient chemical oxygen-iodine laser system in mind. An impinging-jet nozzle was utilized to atomize a H2O2-KOH solution so that the alkaline H2O2/Cl2 reaction might occur in droplet-gas phase with high excitation efficiency. Experimental results indicate that the present generator can yield as high as 80 percent of O2(1Delta) with reasonable O2 flow rate.

LuAG:Pr3+-porphyrin based nanohybrid system for singlet oxygen production: Toward the next generation of PDTX drugs.

PubMed

Popovich, Kseniya; Tomanová, Kateřina; Čuba, Václav; Procházková, Lenka; Pelikánová, Iveta Terezie; Jakubec, Ivo; Mihóková, Eva; Nikl, Martin

2018-02-01

A highly prospective drug for the X-ray induced photodynamic therapy (PDTX), LuAG:Pr 3+ @SiO 2 -PpIX nanocomposite, was successfully prepared by a three step process: photo-induced precipitation of the Lu 3 Al 5 O 12 :Pr 3+ (LuAG:Pr 3+ ) core, sol-gel technique for amorphous silica coating, and a biofunctionalization by attaching the protoporphyrin IX (PpIX) molecules. The synthesis procedure provides three-layer nanocomposite with uniform shells covering an intensely luminescent core. Room temperature radioluminescence (RT RL) spectra as well as photoluminescence (RT PL) steady-state and time resolved spectra of the material confirm the non-radiative energy transfer from the core Pr 3+ ions to the PpIX outer layer. First, excitation of Pr 3+ ions results in the red luminescence of PpIX. Second, the decay measurements exhibit clear evidence of mentioned non-radiative energy transfer (ET). The singlet oxygen generation in the system was demonstrated by the 3'-(p-aminophenyl) fluorescein (APF) chemical probe sensitive to the singlet oxygen presence. The RT PL spectra of an X-ray irradiated material with the APF probe manifest the formation of singlet oxygen due to which enhanced luminescence around 530 nm is observed. Quenching studies, using NaN 3 as an 1 O 2 inhibitor, also confirm the presence of 1 O 2 in the system and rule out the parasitic reaction with OH radicals. To summarize, presented features of LuAG:Pr 3+ @SiO 2 -PpIX nanocomposite indicate its considerable potential for PDTX application. Copyright © 2018 Elsevier B.V. All rights reserved.

Direct participation of DNA in the formation of singlet oxygen and base damage under UVA irradiation.

PubMed

Yagura, Teiti; Schuch, André Passaglia; Garcia, Camila Carrião Machado; Rocha, Clarissa Ribeiro Reily; Moreno, Natália Cestari; Angeli, José Pedro Friedmann; Mendes, Davi; Severino, Divinomar; Bianchini Sanchez, Angelica; Di Mascio, Paolo; de Medeiros, Marisa Helena Gennari; Menck, Carlos Frederico Martins

2017-07-01

UVA light is hardly absorbed by the DNA molecule, but recent works point to a direct mechanism of DNA lesion by these wavelengths. UVA light also excite endogenous chromophores, which causes DNA damage through ROS. In this study, DNA samples were irradiated with UVA light in different conditions to investigate possible mechanisms involved in the induction of DNA damage. The different types of DNA lesions formed after irradiation were determined through the use of endonucleases, which recognize and cleave sites containing oxidized bases and cyclobutane pyrimidine dimers (CPDs), as well as through antibody recognition. The formation of 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxodG) was also studied in more detail using electrochemical detection. The results show that high NaCl concentration and concentrated DNA are capable of reducing the induction of CPDs. Moreover, concerning damage caused by oxidative stress, the presence of sodium azide and metal chelators reduce their induction, while deuterated water increases the amounts of oxidized bases, confirming the involvement of singlet oxygen in the generation of these lesions. Curiously, however, high concentrations of DNA also enhanced the formation of oxidized bases, in a reaction that paralleled the increase in the formation of singlet oxygen in the solution. This was interpreted as being due to an intrinsic photosensitization mechanism, depending directly on the DNA molecule to absorb UVA and generate singlet oxygen. Therefore, the DNA molecule itself may act as a chromophore for UVA light, locally producing a damaging agent, which may lead to even greater concerns about the deleterious impact of sunlight. Copyright © 2017 Elsevier Inc. All rights reserved.

Photochemical properties of squarylium cyanine dyes.

PubMed

Ferreira, D P; Conceição, D S; Ferreira, V R A; Graça, V C; Santos, P F; Vieira Ferreira, L F

2013-11-01

This study presents several new squarylium dyes derived from benzothiazole and benzoselenazole with several structural variations, namely the nature of the heteroaromatic ring and the length of the N,N'-dialkyl groups. Before being investigated in connection with their effect on living cells and/or tissues, these novel compounds were characterized, namely with respect to the determination of their main photophysical parameters. Therefore, a study of the ground state absorption, fluorescence emission (quantum yields and lifetimes) and singlet oxygen generation quantum yields was performed for all the compounds synthesized in order to evaluate their efficiency as photosensitizers. An increase of the alkyl chain length from ethyl to hexyl did not produce a clear change in the fluorescence quantum yields, showing no influence on the photoisomerization process. Heavy atom inclusion (Se instead of S) enhanced the singlet oxygen generation efficiency and decreased the intensity of the fluorescence emission. The external heavy atom effect (I(-) as a counterion instead of CF3SO3(-)) produced a significant increase in the singlet oxygen formation quantum yield (about 20%). Transient absorption studies in aerated and oxygen free samples revealed that the photoisomerization process, which could compete with the triplet state formation for all dyes in solution, is a negligible pathway for the excited state deactivation, in accordance with the rigidity introduced by the squaric ring into the polymethine chain of the dye, both in chloroform and ethanol. However, in the case of the chloroform solution a new transient was detected in air equilibrated solutions, resulting from a reaction of the excited squarylium dye in the singlet state with CHCl3˙, and assigned to the radical cation (SQ(+)˙) of the dye.

"Dark" Singlet Oxygen and Electron Paramagnetic Resonance Spin Trapping as Convenient Tools to Assess Photolytic Drug Degradation.

PubMed

Persich, Peter; Hostyn, Steven; Joie, Céline; Winderickx, Guy; Pikkemaat, Jeroen; Romijn, Edwin P; Maes, Bert U W

2017-05-01

Forced degradation studies are an important tool for a systematic assessment of decomposition pathways and identification of reactive sites in active pharmaceutical ingredients (APIs). Two methodologies have been combined in order to provide a deeper understanding of singlet oxygen-related degradation pathways of APIs under light irradiation. First, we report that a "dark" singlet oxygen test enables the investigation of drug reactivity toward singlet oxygen independently of photolytic irradiation processes. Second, the photosensitizing properties of the API producing the singlet oxygen was proven and quantified by spin trapping and electron paramagnetic resonance analysis. A combination of these techniques is an interesting addition to the forced degradation portfolio as it can be used for (1) revealing unexpected degradation pathways of APIs due to singlet oxygen, (2) clarifying photolytic drug-drug interactions in fixed-dose combinations, and (3) synthesizing larger quantities of hardly accessible oxidative drug degradants. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

O2(a1Δ) quenching in O/O2/O3/CO2/He/Ar mixtures

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-02-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ))+O+M-->2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ)) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ)) quenching were followed by observing the 1268 nm fluorescence of the O2 a1Δ-X3Ε transition. Fast quenching of O2(a1Δ)) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

The effect of axial ligands on the quantum yield of singlet oxygen of new silicon phthalocyanine

NASA Astrophysics Data System (ADS)

Lv, Huafei; Zhang, Xuemei; Yu, Xinxin; Pan, Sujuan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2016-10-01

The singlet oxygen (1O2) production abilitity is an important factor to assess their potential as effective of photosensitizers. In this paper, the 1O2 production rate, production rate constant and quantum yield of silicon(IV) phthalocyanine axially bearing 1-3 generation dendritic substituents were evaluated by a high performance liquid chromatographic method. The results show that the 1O2 production rate and production rate constant of these compounds increase gradually with dendritic generations increase. And the 1O2 quantum yield of silicon(IV) phthalocyanine with first generation dendritic ligand was the highest. This may be due to the isolation effect of the dendritic ligands on the phthalocyanine core. The parameters of the observed 1O2 production properties will provide valuable data for these dendrimer phthalocyanines as promising photosensitizer in PDT application.

Enhanced singlet oxygen generation from PLGA loaded with verteporfin and gold nanoparticles

NASA Astrophysics Data System (ADS)

Deng, Wei; Kautzka, Zofia; Goldys, Ewa M.

2016-12-01

In this study, poly(lactic-co-glycolic acid) (PLGA) nanocomposites were developed by incorporating a photosensitizer, verteporfin and gold nanoparticles into this polymeric matrix and utilised for enhanced photoynamic therapy. Both enhanced fluorescence and singlet oxygen generation from verteporfin were observed in this new formulation under both 425nm LED and 405nm laser illumination. A maximum enhancement factor of 2.5 for fluorescence and 1.84 for 1O2 generation was obtained when the molar ratio of gold:VP was 5:1 and excited at 425 nm, compared with PLGA doped with verteporfin only. The experiment results could be explained by the local electric field enhancement of gold nanoparticles. Furthermore, in vitro cell-killing effect on human pancreatic cancer cells was also demonstrated by using this new formulation following light exposure, indicating the utility of these nanocomposites for enhanced photodynamic therapy.

Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium-Oxygen Battery.

PubMed

Wandt, Johannes; Jakes, Peter; Granwehr, Josef; Gasteiger, Hubert A; Eichel, Rüdiger-A

2016-06-06

Aprotic lithium-oxygen (Li-O2 ) batteries have attracted considerable attention in recent years owing to their outstanding theoretical energy density. A major challenge is their poor reversibility caused by degradation reactions, which mainly occur during battery charge and are still poorly understood. Herein, we show that singlet oxygen ((1) Δg ) is formed upon Li2 O2 oxidation at potentials above 3.5 V. Singlet oxygen was detected through a reaction with a spin trap to form a stable radical that was observed by time- and voltage-resolved in operando EPR spectroscopy in a purpose-built spectroelectrochemical cell. According to our estimate, a lower limit of approximately 0.5 % of the evolved oxygen is singlet oxygen. The occurrence of highly reactive singlet oxygen might be the long-overlooked missing link in the understanding of the electrolyte degradation and carbon corrosion reactions that occur during the charging of Li-O2 cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-vitro singlet oxygen threshold dose at PDT with Radachlorin photosensitizer

NASA Astrophysics Data System (ADS)

Klimenko, V. V.; Shmakov, S. V.; Kaydanov, N. E.; Knyazev, N. A.; Kazakov, N. V.; Rusanov, A. A.; Bogdanov, A. A.; Dubina, M. V.

2017-07-01

In this present study we investigate the Radachlorin photosensitizer accumulation in K562 cells and Hela cells and determined the cell viability after PDT. Using the macroscopic singlet oxygen modeling and cellular photosensitizer concentration the singlet oxygen threshold doses for K562 cells and Hela cells were calculated.

A prototype of an electric-discharge gas flow oxygen-iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

NASA Astrophysics Data System (ADS)

Vagin, N. P.; Ionin, A. A.; Kochetov, I. V.; Napartovich, A. P.; Sinitsyn, D. V.; Yuryshev, N. N.

2017-03-01

The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O2: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions, volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as 100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to 220-230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen-iodine laser based on a slab cryogenic RF discharge.

Synergism between airborne singlet oxygen and a trisubstituted olefin sulfonate for the inactivation of bacteria.

PubMed

Choudhury, Rajib; Greer, Alexander

2014-04-01

The reactivity of a trisubstituted alkene surfactant (8-methylnon-7-ene-1 sulfonate, 1) to airborne singlet oxygen in a solution containing E. coli was examined. Surfactant 1 was prepared by a Strecker-type reaction of 9-bromo-2-methylnon-2-ene with sodium sulfite. Submicellar concentrations of 1 were used that reacted with singlet oxygen by an "ene" reaction to yield two hydroperoxides (7-hydroperoxy-8-methylnon-8-ene-1 sulfonate and (E)-8-hydroperoxy-8-methylnon-6-ene-1 sulfonate) in a 4:1 ratio. Exchanging the H2O solution for D2O where the lifetime of solution-phase singlet oxygen increases by 20-fold led to an ∼2-fold increase in the yield of hydroperoxides pointing to surface activity of singlet oxygen with the surfactant in a partially solvated state. In this airborne singlet oxygen reaction, E. coli inactivation was monitored in the presence and absence of 1 and by a LIVE/DEAD cell permeabilization assay. It was shown that the surfactant has low dark toxicity with respect to the bacteria, but in the presence of airborne singlet oxygen, it produces a synergistic enhancement of the bacterial inactivation. How the ene-derived surfactant hydroperoxides can provoke (1)O2 toxicity and be of general utility is discussed.

Steady-state and time-resolved studies on the photophysical properties of fullerene-pyropheophorbide a complexes in polar and nonpolar solvents

NASA Astrophysics Data System (ADS)

Ermilov, E. A.; Al-Omari, S.; Helmreich, M.; Jux, N.; Hirsch, A.; Röder, B.

2004-04-01

A novel monofullerene-bis(pyropheophorbide a) dyad has been photophysically characterized by steady-state as well as time-resolved techniques. It was revealed that in this complex strong and fast quenching of the first excited singlet state of the pyropheophorbide a (pyroPheo) molecule occurs by efficient photoinduced electron transfer to the fullerene moiety in both polar (DMF) and nonpolar (toluene) solvents. In DMF the energy of the charge-separated state is 0.94 eV and it undergoes directly transition to the ground state resulting in a very low value of photosensitized singlet oxygen generation. In contrast to the situation in a polar solvent, in toluene the charge-separated state lies above the exited triplet state of pyroPheo as well as that of C 60. It has been shown that in a nonpolar solvent a sufficient amount of singlet oxygen was generated by energy transfer from the excited triplet state of pyroPheo which has been populated via relaxation of the charge-separated state.

Singlet Oxygen Detection Using Red Wine Extracts as Photosensitizers.

PubMed

Lagunes, Irene; Vázquez-Ortega, Fernanda; Trigos, Ángel

2017-09-01

Moderate consumption of red wine provides beneficial effects to health. This is attributed to polyphenol compounds present in wine such as resveratrol, quercetin, gallic acid, rutin, and vanillic acid. The amount of these antioxidants is variable; nevertheless, the main beneficial effects of red wine are attributed to resveratrol. However, it has been found that resveratrol and quercetin are able to photosensitize singlet oxygen generation and conversely, gallic acid acts as quencher. Therefore, and since resveratrol and quercetin are some of the most important antioxidants reported in red wines, the aim of this research was to evaluate the photosensitizing ability of 12 red wine extracts through photo-oxidation of ergosterol. The presence of 1 O 2 was detected by ergosterol conversion into peroxide of ergosterol through 1 H NMR analysis. Our results showed that 10 wine extracts were able to act as photosensitizers in the generation of singlet oxygen. The presence of 1 O 2 can damage other compounds of red wine and cause possible organoleptic alterations. Finally, although the reaction conditions employed in this research do not resemble the inherent conditions in wine making processing or storing, or even during its consumption, this knowledge could be useful to prevent possible pro-oxidant effects and avoid detrimental effects in red wines. © 2017 Institute of Food Technologists®.

Luminescence spectroscopic observation of singlet oxygen formation in extra virgin olive oil as affected by irradiation light wavelengths, 1,4-diazabicyclo[2.2.2]octane, irradiation time, and oxygen bubbling.

PubMed

Jung, Mun Y; Choi, Dong S; Park, Ki H; Lee, Bosoon; Min, David B

2011-01-01

A spectrofluorometer equipped with a highly sensitive near-IR InGaAs detector was used for the direct visualization of singlet oxygen emission at 1268 nm in olive oil during light irradiation with various different wavelengths. The virgin olive oil in methylene chloride (20% w/v, oxygen saturated) was irradiated at the 301, 417, 454, 483, and 668 nm, then the emission at 1268 nm, singlet oxygen dimole decaying was observed. The result showed the highest production of (1)O(2) with light irradiation at 417 nm, and followed by at 668 nm in virgin olive oil, indicating that pheophytin a and chlorophyll a were the most responsible components for the production of singlet oxygen. The UV light irradiations at the wavelength of 200, 250, and 300 nm did not induce any detectable luminescence emission at 1268 nm, but 350 nm produced weak emission at 1269 nm. The quantity of (1)O(2) produced with excitation at 350 nm was about 1/6 of that of irradiation at 417 nm. Addition of an efficient (1)O(2) quencher, 1,4-diazabicyclo[2.2.2]octane, in virgin olive oil in methylene chloride greatly decreased the luminescence emission at 1268 nm, confirming the singlet oxygen production in olive oil. Singlet oxygen production was more efficient in oxygen-purged virgin olive oil than in oxygen non-purged olive oil. This represents first report on the direct observation of singlet oxygen formation in olive oil as well as in real-food system after visible light illumination. Practical Application: The present results show the positive evidence of the singlet oxygen involvement in rapid oxidative deterioration of virgin olive oil under visible light. This paper also shows the effects of different wavelength of light irradiation on the formation of singlet oxygen in olive oil. The present results would provide important information for the understanding of the mechanism involved in rapid oxidative quality deterioration of virgin olive oil under light illumination and for searching the preventive methods of deterioration of olive oil quality under light.

SU-E-T-191: First Principle Calculation of Quantum Yield in Photodynamic Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abolfath, R; Guo, F; Chen, Z

Purpose: We present a first-principle method to calculate the spin transfer efficiency in oxygen induced by any photon fields especially in MeV energy range. The optical pumping is mediated through photosensitizers, e.g., porphyrin and/or ensemble of quantum dots. Methods: Under normal conditions, oxygen molecules are in the relatively non-reactive triplet state. In the presence of certain photosensitizer compounds such as porphyrins, electromagnetic radiation of specific wavelengths can excite oxygen to highly reactive singlet state. With selective uptake of photosensitizers by certain malignant cells, photon irradiation of phosensitized tumors can lead to selective killing of cancer cells. This is the basismore » of photodynamic therapy (PDT). Despite several attempts, PDT has not been clinically successful except in limited superficial cancers. Many parameters such as photon energy, conjugation with quantum dots etc. can be potentially combined with PDT in order to extend the role of PDT in cancer management. The key quantity for this optimization is the spin transfer efficiency in oxygen by any photon field. The first principle calculation model presented here, is an attempt to fill this need. We employ stochastic density matrix description of the quantum jumps and the rate equation methods in quantum optics based on Markov/Poisson processes and calculate time evolution of the population of the optically pumped singlet oxygen. Results: The results demonstrate the feasibility of our model in showing the dependence of the optical yield in generating spin-singlet oxygen on the experimental conditions. The adjustable variables can be tuned to maximize the population of the singlet oxygen hence the efficacy of the photodynamic therapy. Conclusion: The present model can be employed to fit and analyze the experimental data and possibly to assist researchers in optimizing the experimental conditions in photodynamic therapy.« less

Regulation of singlet oxygen-induced apoptosis by cytosolic NADP+-dependent isocitrate dehydrogenase.

PubMed

Kim, Sun Yee; Lee, Su Min; Tak, Jean Kyoung; Choi, Kyeong Sook; Kwon, Taeg Kyu; Park, Jeen-Woo

2007-08-01

Singlet oxygen is a highly reactive form of molecular oxygen that may harm living systems by oxidizing critical cellular macromolecules and it also promotes deleterious processes such as cell death. Recently, we demonstrated that the control of redox balance and the cellular defense against oxidative damage are the primary functions of cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDPc) through supplying NADPH for antioxidant systems. In this report, we demonstrate that modulation of IDPc activity in HL-60 cells regulates singlet oxygen-induced apoptosis. When we examined the protective role of IDPc against singlet oxygen-induced apoptosis with HL-60 cells transfected with the cDNA for mouse IDPc in sense and antisense orientations, a clear inverse relationship was observed between the amount of IDPc expressed in target cells and their susceptibility to apoptosis. The results suggest that IDPc plays an important protective role in apoptosis of HL-60 cells induced by singlet oxygen.

A tandem mass spectrometric method for singlet oxygen measurement.

PubMed

Karonen, Maarit; Mattila, Heta; Huang, Ping; Mamedov, Fikret; Styring, Stenbjörn; Tyystjärvi, Esa

2014-01-01

Singlet oxygen, a harmful reactive oxygen species, can be quantified with the substance 2,2,6,6-tetramethylpiperidine (TEMP) that reacts with singlet oxygen, forming a stable nitroxyl radical (TEMPO). TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we designed an ultra-high-performance liquid chromatographic-tandem mass spectrometric (UHPLC-ESI-MS/MS) quantification method for TEMPO and showed that the method based on multiple reaction monitoring (MRM) can be used for the measurements of singlet oxygen from both nonbiological and biological samples. Results obtained with both UHPLC-ESI-MS/MS and EPR methods suggest that plant thylakoid membranes produce 3.7 × 10(-7) molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000 μmol m(-2 ) s(-1). © 2014 The American Society of Photobiology.

Microscopic time-resolved imaging of singlet oxygen by delayed fluorescence in living cells.

PubMed

Scholz, Marek; Dědic, Roman; Hála, Jan

2017-11-08

Singlet oxygen is a highly reactive species which is involved in a number of processes, including photodynamic therapy of cancer. Its very weak near-infrared emission makes imaging of singlet oxygen in biological systems a long-term challenge. We address this challenge by introducing Singlet Oxygen Feedback Delayed Fluorescence (SOFDF) as a novel modality for semi-direct microscopic time-resolved wide-field imaging of singlet oxygen in biological systems. SOFDF has been investigated in individual fibroblast cells incubated with a well-known photosensitizer aluminium phthalocyanine tetrasulfonate. The SOFDF emission from the cells is several orders of magnitude stronger and much more readily detectable than the very weak near-infrared phosphorescence of singlet oxygen. Moreover, the analysis of SOFDF kinetics enables us to estimate the lifetimes of the involved excited states. Real-time SOFDF images with micrometer spatial resolution and submicrosecond temporal-resolution have been recorded. Interestingly, a steep decrease in the SOFDF intensity after the photodynamically induced release of a photosensitizer from lysosomes has been demonstrated. This effect could be potentially employed as a valuable diagnostic tool for monitoring and dosimetry in photodynamic therapy.

Effect of the solution temperature in a singlet-oxygen generator on the formation of active medium in an ejector oxygen - iodine laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagidullin, M V; Nikolaev, V D; Svistun, M I

2002-02-28

The influence of the solution temperature in a singlet-oxygen generator on the formation of the active medium in the ejector oxygen - iodine laser is investigated. The following parameters of the active medium at the solution temperature -20{sup 0}C are obtained: the gain is 7.2 x 10{sup -3} cm{sup -1}, the Mach number is M=2, the temperature is 205 K, and the static pressure is 9.3 mmHg. As the solution temperature is increased to -4{sup 0}C, the gain decreases to 5 x 10{sup 3} cm{sup -1}, the Mach number decreases to 1.78, while the temperature and the static pressure increasemore » to 241 K and 10.7 mmHg, respectively. As the solution temperature increases from -20 to -4{sup 0}C, the losses in O{sub 2}({sup 1}{Delta}) increase by less than 20%, while the dissociation efficiency of molecular iodine decreases by less than 21%. (lasers, active media)« less

Quenching of I(2P 1/2) by O 3 and O( 3P)

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Antonov, I. O.; Ruffner, S.; Heaven, M. C.

2006-02-01

Oxygen-iodine lasers that utilize electrical or microwave discharges to produce singlet oxygen are currently being developed. The discharge generators differ from conventional chemical singlet oxygen generators in that they produce significant amounts of atomic oxygen. Post-discharge chemistry includes channels that lead to the formation of ozone. Consequently, removal of I(2P 1/2) by O atoms and O 3 may impact the efficiency of discharge driven iodine lasers. In the present study we have measured the rate constants for quenching of I(2P 1/2) by O( 3P) atoms and O 3 using pulsed laser photolysis techniques. The rate constant for quenching by O 3, 1.8x10 -12 cm 3 s -1, was found to be a factor of five smaller than the literature value. The rate constant for quenching by O( 3P) was 1.2x10 -11 cm 3 s -1. This was six times larger than a previously reported upper bound, but consistent with estimates obtained by modeling the kinetics of discharge-driven laser systems.

Chlorophyll catalyse the photo-transformation of carcinogenic benzo[a]pyrene in water

PubMed Central

Luo, Lijuan; Lai, Xueying; Chen, Baowei; Lin, Li; Fang, Ling; Tam, Nora F. Y.; Luan, Tiangang

2015-01-01

Algal blooms cause great damage to water quality and aquaculture. However, this study showed that dead algal cells and chlorophyll could accelerate the photo-transformation of benzo[a]pyrene (BaP), a ubiquitous and persistent pollutant with potently mutagenic and carcinogenic toxicities, under visible light irradiation. Chlorophyll was found to be the major active substance in dead algal cells, and generated a high level of singlet oxygen to catalyse the photo-transformation of BaP. According to various BaP metabolites formed, the degradation mechanism was proposed as that chlorophyll in dead algal cells photo-oxidized BaP to quinones via photocatalytic generation of singlet oxygen. The results provided a good insight into the role of chlorophyll in the photo-transformation of organic contaminants and could be a possible remediation strategy of organic pollutants in natural environment. PMID:26239357

GUN4-Protoporphyrin IX Is a Singlet Oxygen Generator with Consequences for Plastid Retrograde Signaling*

PubMed Central

Tarahi Tabrizi, Shabnam; Sawicki, Artur; Zhou, Shuaixiang; Luo, Meizhong; Willows, Robert D.

2016-01-01

The genomes uncoupled 4 (GUN4) protein is a nuclear-encoded, chloroplast-localized, porphyrin-binding protein implicated in retrograde signaling between the chloroplast and nucleus, although its exact role in this process is still unclear. Functionally, it enhances Mg-chelatase activity in the chlorophyll biosynthesis pathway. Because GUN4 is present only in organisms that carry out oxygenic photosynthesis and because it binds protoporphyrin IX (PPIX) and Mg-PPIX, it has been suggested that it prevents production of light- and PPIX- or Mg-PPIX-dependent reactive oxygen species. A chld-1/GUN4 mutant with elevated PPIX has a light-dependent up-regulation of GUN4, implicating this protein in light-dependent sensing of PPIX, with the suggestion that GUN4 reduces PPIX-generated singlet oxygen, O2(a1Δg), and subsequent oxidative damage (Brzezowski, P., Schlicke, H., Richter, A., Dent, R. M., Niyogi, K. K., and Grimm, B. (2014) Plant J. 79, 285–298). In direct contrast, our results show that purified GUN4 and oxidatively damaged ChlH increase the rate of PPIX-generated singlet oxygen production in the light, by a factor of 5 and 10, respectively, when compared with PPIX alone. Additionally, the functional GUN4-PPIX-ChlH complex and ChlH-PPIX complexes generate O2(a1Δg) at a reduced rate when compared with GUN4-PPIX. As O2(a1Δg) is a potential plastid-to-nucleus signal, possibly through second messengers, light-dependent O2(a1Δg) generation by GUN4-PPIX is proposed to be part of a signal transduction pathway from the chloroplast to the nucleus. GUN4 thus senses the availability and flux of PPIX through the chlorophyll biosynthetic pathway and also modulates Mg-chelatase activity. The light-dependent O2(a1Δg) generation from GUN4-PPIX is thus proposed as the first step in retrograde signaling from the chloroplast to the nucleus. PMID:26969164

Photodynamic inactivation of Escherichia coli - Correlation of singlet oxygen kinetics and phototoxicity.

PubMed

Müller, Alexander; Preuß, Annegret; Röder, Beate

2018-01-01

Photodynamic inactivation (PDI) of bacteria may play a major role in facing the challenge of the ever expanding antibiotic resistances. Here we report about the direct correlation of singlet oxygen luminescence kinetics and phototoxicity in E. coli cell suspension under PDI using the widely applied cationic photosensitizer TMPyP. Through direct access to the microenvironment, the time resolved investigation of singlet oxygen luminescence plays a key role in understanding the photosensitization mechanism and inactivation pathway. Using the homemade set-up for highly sensitive time resolved singlet oxygen luminescence detection, we show that the cationic TMPyP is localized predominantly outside the bacterial cells but in their immediate vicinity prior to photodynamic inactivation. Throughout following light exposure, a clear change in singlet oxygen kinetics indicates a redistribution of photosensitizer molecules to at least one additional microenvironment. We found the signal kinetics mirrored in cell viability measurements of equally treated samples from same overnight cultures conducted in parallel: A significant drop in cell viability of the illuminated samples and stationary viability of dark controls. Thus, for the system investigated in this work - a Gram-negative model bacteria and a well-known PS for its PDI - singlet oxygen kinetics correlates with phototoxicity. This finding suggests that it is well possible to evaluate PDI efficiency directly via time resolved singlet oxygen detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Singlet Oxygen Scavenging Activity and Cytotoxicity of Essential Oils from Rutaceae

PubMed Central

Ao, Yoko; Satoh, Kazue; Shibano, Katsushige; Kawahito, Yukari; Shioda, Seiji

2008-01-01

Since we have been exposed to excessive amounts of stressors, aromatherapy for the relaxation has recently become very popular recently. However, there is a problem which responds to light with the essential oil used by aromatherapy. It is generally believed that singlet oxygen is implicated in the pathogenesis of various diseases such as light-induced skin disorders and inflammatory responses. Here we studied whether essential oils can effectively scavenge singlet oxygen upon irradiation, using the electron spin resonance (ESR) method. Green light was used to irradiate twelve essential oils from rutaceae. Among these twelve essential oils, eight were prepared by the expression (or the compression) method (referred to as E oil), and four samples were prepared by the steam distillation method (referred to as SD oil). Five E oils enhanced singlet oxygen production. As these essential oils may be phototoxic, it should be used for their use whit light. Two E oils and three SD oils showed singlet oxygen scavenging activity. These results may suggest that the antioxidant activity of essential oils are judged from their radical scavenging activity. Essential oils, which enhance the singlet oxygen production and show higher cytotoxicity, may contain much of limonene. These results suggest that limonene is involved not only in the enhancement of singlet oxygen production but also in the expression of cytotoxic activity, and that attention has to be necessary for use of blended essential oils. PMID:18648659

Singlet oxygen feedback delayed fluorescence of protoporphyrin IX in organic solutions.

PubMed

Vinklárek, Ivo S; Scholz, Marek; Dědic, Roman; Hála, Jan

2017-04-12

Delayed fluorescence (DF) of protoporphyrin IX (PpIX) has been recently proposed as a tool for monitoring of mitochondrial oxygen tension in vivo as well as for observation of the effectiveness of photodynamic therapy (PDT) [E. G. Mik, Anesth. Analg., 2013, 117, 834-346; F. Piffaretti et al., J. Biomed. Opt., 2012, 17, 115007]. However, the efficiency of the mechanism of thermal activation (E-type DF), which was considered in the papers, is limited due to a large energy gap between the first excited singlet and the first triplet state of PpIX at room or body temperatures. Moreover, the energy gap is roughly equal to other porphyrinoid photosensitizers that generate DF mostly through the Singlet Oxygen Feedback-Induced mechanism (SOFDF) under certain conditions [M. Scholz and R. Dědic, Singlet Oxygen: Applications in Biosciences and Nanosciences, 2016, vol. 2, pp. 63-81]. The mechanisms of delayed fluorescence of PpIX dissolved either in dimethylformamide (DMF) or in the mixture of DMF with ethylene glycol (EG) were investigated at atmospheric partial pressure of oxygen by means of a simultaneous time-resolved detection of 1 O 2 phosphorescence and PpIX DF which makes a direct comparison of the kinetics and lifetimes of both the luminescence channels possible. Samples of PpIX (100 μM) exhibit concave DF kinetics, which is a typical footprint of the SOFDF mechanism. The dramatic decrease in the DF intensity after adding a selective 1 O 2 quencher sodium azide (NaN 3 , 10 mM) proves that >90% of DF is indeed generated through SOFDF. Moreover, the analysis of the DF kinetics in the presence of NaN 3 implies that the second significant mechanism of DF generation is the triplet-triplet annihilation (P-type DF). The bimolecular mechanism of DF was further confirmed by the decrease of the DF intensity in the more viscous mixture DMF/EG and by the increase of the ratio of DF to the prompt fluorescence (PF) intensity with the increasing excitation intensity. These results show the significant role of the SOFDF mechanism in the DF of PpIX at high concentrations and at atmospheric partial pressure of oxygen and should be considered when developing diagnostic tools for clinical applications.

The effect of laparotomy on hydroxyl radicals, singlet oxygen and antioxidants measured by EPR method in the tails of rats.

PubMed

Fricova, Jitka; Stopka, Pavel; Krizova, Jana; Yamamotova, Anna; Rokyta, Richard

2009-01-01

The aim of the study was to demonstrate that direct measurement of hydroxyl radicals and singlet oxygen in the tail of living rats is possible. The basic level of hydroxyl radicals and singlet oxygen were measured and the effects of antioxidants on their levels were studied in the tail of living anaesthetized rats after acute postoperative pain. Laparotomy was performed as the source of acute abdominal pain. After closure of the abdominal cavity, the animals began to awaken within 30-60 minutes. They were left to recover for 2-3 hours; then they were reanesthetized and the effect of antioxidants was measured on the numbers of hydroxyl radicals and singlet oxygen via blood in the tail. The laparotomy was preformed under general anesthesia (Xylazin and Ketamin) using Wistar rats. After recovery and several hours of consciousness they were reanaesthetized and free radicals and singlet oxygen were measured. An antioxidant mixture (vitamins A, C, D and Selenium) was administered intramuscularly prior to the laparotomy. All measurements were done on the tail of anaesthetized animals. In this particular article, the effect of antioxidants is only reported for hydroxyl radicals. After laparotomy, which represented both somatic and visceral pain, hydroxyl radicals and singlet oxygen were increased. Antioxidant application prior to laparotomy decreased the numbers of hydroxyl radicals. Results are in agreement with our previous finding regarding the increase in hydroxyl free radicals and singlet oxygen following nociceptive stimulation, in this case a combination of both somatic and visceral pain. The administered antioxidants mitigated the increase. This is further confirmation that direct measurement of free radicals and singlet oxygen represents a very useful method for the biochemical evaluation of pain and nociception.

Inactivation of biologically active dna by gamma ray induced superoxide radicals and their dismutation products singlet molecular oxygen and hydrogen peroxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanhemmen, J.J.; Meuling, W.J.A.

1975-01-01

The reactivity of gamma ray induced superoxide radicals and dismutation products (singlet molecular oxygen and hydrogen peroxide) with DNA were studied. Superoxide dismutase, which removes superoxide radicals and inhibits the formation of singlet oxygen, protects biologically active DNA (OX174 RF) against inactivation by ionizing radiation. Catalase, which removes hydrogen peroxide, also protects the DNA. Attempts with various chemical sources of singlet oxygen to determine whether this species inactivates DNA did not yield an unequivocal answer. It was concluded that a combination of the protonated form of the superoxide radical and hydrogen peroxide inactivates DNA. (Author) (GRA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iu, Kaikong; Thomas, J.K.

Direct time-resolved studies of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) phosphorescence ({sup 3}{Sigma}{sub g} {sup {minus}}O{sub 2} ({nu} = 0) {l arrow} {sup 1}{Delta}{sub g}O{sub 2} ({nu} = 0); 1,270 nm) in heterogeneous silica gel/cyclohexane systems are presented. Singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) is created through a photosensitization process on silica gel surfaces. The experimental results show that the lifetimes of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) in both porous and compressed fumed silica/gel cyclohexane systems are significantly less than that in liquid cyclohexane. The shortened singlet molecular oxygen lifetime is due mainly to quenching bymore » adsorbed water and silanol groups on the silica gel surface. In addition, monoamines coadsorbed on the silica gel surface do not quench singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}); however, diamines such as DABCO or piperazine maintain their quenching activity, but the quenching kinetics are not of the Stern-Volmer type. The singlet molecular oxygen lifetime increases on loading the porous silica gel/cyclohexane system with monoamine. Coadsorption of piperazine increases quenching of {sup 1}{Delta}{sub g} O{sub 2} by DABCO.« less

Singlet oxygen-induced photodegradation of the polymers and dyes in optical sensing materials and the effect of stabilizers on these processes.

PubMed

Enko, Barbara; Borisov, Sergey M; Regensburger, Johannes; Bäumler, Wolfgang; Gescheidt, Georg; Klimant, Ingo

2013-09-12

A comprehensive study of photodegradation processes in optical sensing materials caused by photosensitized singlet oxygen in different polymers is presented. The stabilities of the polymers are accessed in the oxygen consumption measurements performed with help of optical oxygen sensors. Polystyrene and poly(phenylsilesquioxane) are found to be the most stable among the polymers investigated, whereas poly(2,6-dimethyl-p-phenylene oxide) and particularly poly(methyl methacrylate) and their derivatives show the fastest oxygen consumption. The effect of the stabilizers (singlet oxygen quenchers) on the oxygen consumption rates, the photostability of the sensitizer, and the total photon emission (TPE) by singlet oxygen is studied. 1,4-Diazabicyclo[2.2.2]octane (DABCO) was found to significantly reduce both the TPE and the oxygen consumption rates, indicating its role as a physical quencher of singlet oxygen. The addition of DABCO also significantly improved the photostability of the sensitizer. The N-alkylated derivative of DABCO and DABCO covalently grafted to the polystyrene backbone are prepared in an attempt to overcome the volatility and water solubility of the quencher. These derivatives as well as other tertiary amines investigated were found to be inefficient as stabilizing agents, and some of them even negatively affected the oxygen consumption rates.

Adapting BODIPYs to singlet oxygen production on silica nanoparticles.

PubMed

Epelde-Elezcano, Nerea; Prieto-Montero, Ruth; Martínez-Martínez, Virginia; Ortiz, María J; Prieto-Castañeda, Alejandro; Peña-Cabrera, Eduardo; Belmonte-Vázquez, José L; López-Arbeloa, Iñigo; Brown, Ross; Lacombe, Sylvie

2017-05-31

A modified Stöber method is used to synthesize spherical core-shell silica nanoparticles (NPs) with an external surface functionalized by amino groups and with an average size around 50 nm. Fluorescent dyes and photosensitizers of singlet oxygen were fixed, either separately or conjointly, respectively in the core or in the shell. Rhodamines were encapsulated in the core with relatively high fluorescence quantum yields (Φ fl ≥ 0.3), allowing fluorescence tracking of the particles. Various photosensitizers of singlet oxygen (PS) were covalenty coupled to the shell, allowing singlet oxygen production. The stability of NP suspensions strongly deteriorated upon grafting the PS, affecting their apparent singlet oxygen quantum yields. Agglomeration of NPs depends both on the type and on the amount of grafted photosensitizer. New, lab-made, halogenated 4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY) grafted to the NPs achieved higher singlet oxygen quantum yields (Φ Δ ∼ 0.35-0.40) than Rose Bengal (RB) grafted NPs (Φ Δ ∼ 0.10-0.27). Finally, we combined both fluorescence and PS functions in the same NP, namely a rhodamine in the silica core and a BODIPY or RB grafted in the shell, achieving the performance Φ fl ∼ 0.10-0.20, Φ Δ ∼ 0.16-0.25 with a single excitation wavelength. Thus, proper choice of the dyes, of their concentrations inside and on the NPs and the grafting method enables fine-tuning of singlet oxygen production and fluorescence emission.

Liquid-liquid reaction of hydrogen peroxide and sodium hypochlorite for the production of singlet oxygen in a centrifugal flow singlet oxygen generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui Rongrong; Deng Liezheng; Shi Wenbo

An attempt is made to produce gas-phase singlet oxygen O{sub 2}(a{sup 1{Delta}}{sub g}) in a liquid-liquid reaction between acidic hydrogen peroxide (AHP) and sodium hypochlorite (NaOCl). The attempt arises from the fact that basic hydrogen peroxide (BHP) has long been the prime source for producing singlet delta oxygen through its reaction with chlorine. However, BHP suffers from the defect of being unstable during storage. Exploratory experiments were performed in a centrifugal flow singlet oxygen generator (CF-SOG) with two streams of solutions, AHP and NaOCl, mixed in a slit nozzle and then injected into the arc-shaped concavity in the CF-SOG tomore » form a rotating liquid flow with a remarkable centrifugal force. With the help of this centrifugal force, the product of the O{sub 2}({sup 1{Delta}}) reaction was quickly separated from the liquid phase. The gas-phase O{sub 2}({sup 1{Delta}}) was detected via the spectrum of O{sub 2}({sup 1{Delta}}) cooperative dimolecular emission with a CCD spectrograph. Experimental results show that it is feasible to produce gas-phase O{sub 2}({sup 1{Delta}}) from the AHP + NaOCl reaction, and the stronger the acidity, the more efficient the O{sub 2}({sup 1{Delta}}) production. However, since in the AHP + NaOCl reaction, Cl{sub 2} unavoidably appears as a byproduct, its catalytic action on the decomposition of H{sub 2}O{sub 2} into ground-state O{sub 2} remains a major obstacle to utilising the AHP + NaOCl reaction in producing gas-phase O{sub 2}({sup 1{Delta}}). Qualitative interpretation shows that the AHP + NaOCl reaction is virtually the reaction of interaction of molecular H{sub 2}O{sub 2} with molecular HOCl, its mechanism being analogous to that of reaction of BHP with Cl{sub 2}, where HOOCl is the key intermediate. It is difficult to form the intermediate HOOCl via the H{sub 2}O{sub 2} + NaOCl reaction in a basic medium, thus gas-phase O{sub 2}({sup 1{Delta}}) cannot be obtained in appreciable quantities. (active media)« less

Heterometallic Ru-Pt metallacycle for two-photon photodynamic therapy.

PubMed

Zhou, Zhixuan; Liu, Jiangping; Rees, Thomas W; Wang, Heng; Li, Xiaopeng; Chao, Hui; Stang, Peter J

2018-05-29

As an effective and noninvasive treatment of various diseases, photodynamic therapy (PTD) relies on the combination of light, a photosensitizer, and oxygen to generate cytotoxic reactive oxygen species that can damage malignant tissue. Much attention has been paid to covalent modifications of the photosensitizers to improve their photophysical properties and to optimize the pathway of the photosensitizers interacting with cells within the target tissue. Herein we report the design and synthesis of a supramolecular heterometallic Ru-Pt metallacycle via coordination-driven self-assembly. While inheriting the excellent photostability and two-photon absorption characteristics of the Ru(II) polypyridyl precursor, the metallacycle also exhibits red-shifted luminescence to the near-infrared region, a larger two-photon absorption cross-section, and higher singlet oxygen generation efficiency, making it an excellent candidate as a photosensitizer for PTD. Cellular studies reveal that the metallacycle selectively accumulates in mitochondria and nuclei upon internalization. As a result, singlet oxygen generated by photoexcitation of the metallacycle can efficiently trigger cell death via the simultaneous damage to mitochondrial function and intranuclear DNA. In vivo studies on tumor-bearing mice show that the metallacycle can efficiently inhibit tumor growth under a low light dose with minimal side effects. The supramolecular approach presented in this work provides a paradigm for the development of PDT agents with high efficacy.

[Specialties of singlet oxygen and ozone inhalations action on lipoperozydation and antioxidant system of rats blood and tissues].

PubMed

Martusevich, A A; Martusevich, A K; Peretiagin, S P

2013-09-01

The aim of this work was the analysis of singlet oxygen and the ozone effect on lipid peroxidation and antioxidant activity of rat organs and blood. Wistar rats were randomly divided into five groups: control group (without any manipulations; n = 10) and four main groups (n = 10 in each group) with inhalations by dry, moisture and oil-processed ozone-oxygen mixture (ozone concentration 60 micro g/l) or singlet oxygen, respectively. Activity of pro- and antioxidant systems was estimated in blood and tissues (lungs, heart, liver and kidney) by inducing biochemiluminescence. Singlet oxygen was shown to exert the "mildest" effect with stimulation of blood antioxidant potential and saving tissue oxidative potential without hyperactivation of lipid peroxidation. Use of moistened ozone-oxygen mixture caused moderate stimulating action on antioxidant re serves of blood and tissues. Dry ozone-oxygen mixture clearly decreased lipid peroxidation intensity.

Transient absorption spectroscopy of a monofullerene C60-bis-(pyropheophorbide a) molecular system in polar and nonpolar environments

NASA Astrophysics Data System (ADS)

Al Omari, S.; Ermilov, E. A.; Helmreich, M.; Jux, N.; Hirsch, A.; Röder, B.

2004-09-01

The population dynamics of the excited and ground states of the monofullerene-bis (pyropheophorbide a) complex (FP1) were studied in polar (DMF) and nonpolar (toluene) solvents using picosecond transient absorption techniques. A strong quenching of the fluorescence signal of FP1 was observed in both solvents, in comparison to the fluorescence of bis (pyropheophorbide a) (P2). This quenching is due to an intramolecular photoinduced electron transfer from the pyropheophorbide a (pyroPheo) moiety to the fullerene C60 monoadduct. In DMF the charge-separated (CS) state of FP1 has a lifetime of 0.32 ns and undergoes a direct transition to the ground state, resulting in a very low value of photosensitised singlet oxygen generation. In toluene, energy transfer from the first excited triplet state of pyroPheo, which has been populated via relaxation of the CS state, generates a considerable amount of singlet oxygen. The lifetime of the CS state in the nonpolar solvent was estimated to be 0.29 ns. It was also shown that in both DMF and toluene the first excited singlet state as well as the triplet state of the fullerene moiety in FP1 are not occupied.

Photoinduced DNA damage and cytotoxicity by a triphenylamine-modified platinum-diimine complex.

PubMed

Zhang, Zhigang; Dai, Ruihui; Ma, Jiajia; Wang, Shuying; Wei, Xuehong; Wang, Hongfei

2015-02-01

Many planar photosensitizers tend to self-aggregate via van der Waals interactions between π-conjugated systems. The self-aggregation of the photosensitizer may reduce the efficiency of the photosensitizer to generate singlet oxygen, thereby diminishing its photodynamic activity. Efforts have been made to improve the photodynamic activity of bis-(o-diiminobenzosemiquinonato)platinum(II) which has planar geometry by the introduction of the sterically hindered triphenylamine moiety into the ligand. Herein we report the photoinduced DNA damage and cytotoxicity by a triphenylamine-modified platinum-diimine complex in red light studied by fluorescence spectra, agarose gel assay and cell viability assay. The results suggest that the triphenylamine-modified platinum-diimine complex has better capability to generate singlet oxygen than bis-(o-diiminobenzosemiquinonato)platinum(II), and it can induce DNA damage in red light, causing high photocytotoxicity in HepG-2 cells in vitro. Copyright © 2014 Elsevier Inc. All rights reserved.

Rose bengal-grafted biodegradable microcapsules: singlet-oxygen generation and cancer-cell incapacitation.

PubMed

Wang, Xiao-Lei; Zeng, Yu; Zheng, Yan-Zhen; Chen, Jian-Feng; Tao, Xia; Wang, Ling-Xuan; Teng, Yan

2011-09-26

Rose bengal-grafted chitosan (RB-CHI), synthesized through dehydration between amino and carboxyl functional groups under mild conditions, was coated onto the outer layer of preformed biodegradable microcapsules consisting of sodium alginate and chitosan. The fabricated photosensitive microcapsules were characterized by optical microscopy, scanning electron microscopy, and confocal laser scanning microscopy. The assembled materials maintained intact spherical morphology and thus showed good ability to form thin films. Electron spin resonance spectroscopy allowed direct observation of the generation of singlet oxygen ((1)O(2)) from photosensitive microcapsules under light excitation at about 545 nm. Furthermore, with increasing light radiation, the content of (1)O(2) increased, as detected by a chemical probe. In vitro cellular toxicity assays showed that RB-CHI-coated photosensitive microcapsules exhibit good biocompatibility in darkness and high cytotoxicity after irradiation, and could provide new photoresponsive drug-delivery vehicles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of singlet oxygen generation in Vit C-Cu2+ -LDL system by chemiluminescence method

NASA Astrophysics Data System (ADS)

Wang, Juan; Xing, Da; Tan, Shici; Tang, Yonghong; He, Yonghong

2002-04-01

In this study, by chemiluminescence method using a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7- dihydroimidazo[1,2-a]pyrazin-3-one (MCLA), as a selective and sensitive chemiluminescence probe, singlet oxygen (1O2) formation was observed in the vit C- LDL-Cu2+ reaction system. Another experimental evidence for the generation of 1O2 was the quenching effect of sodium azide (NaN3) on vit C-induced chemiluminescence in the reaction mixture of LDL- Cu2+-MCLA. Analysis based on the experimental results indicated the plausible reaction mechanism is that vit C converts Cu2+ to its reduced state and vit C becomes vit C radical itself, thereby stimulating the formation of peroxyl radicals, and bimolecular reaction of peroxyl radicals results in 1O2 production in the above systems.

Lysozyme oxidation by singlet molecular oxygen: Peptide characterization using [18 O]-labeling oxygen and nLC-MS/MS.

PubMed

Marques, Emerson Finco; Medeiros, Marisa H G; Di Mascio, Paolo

2017-11-01

Singlet molecular oxygen ( 1 O 2 ) is generated in biological systems and reacts with different biomolecules. Proteins are a major target for 1 O 2 , and His, Tyr, Met, Cys, and Trp are oxidized at physiological pH. In the present study, the modification of lysozyme protein by 1 O 2 was investigated using mass spectrometry approaches. The experimental findings showed methionine, histidine, and tryptophan oxidation. The experiments were achieved using [ 18 O]-labeled 1 O 2 released from thermolabile endoperoxides in association with nano-scale liquid chromatography coupled to electrospray ionization mass spectrometry. The structural characterization by nLC-MS/MS of the amino acids in the tryptic peptides of the proteins showed addition of [ 18 O]-labeling atoms in different amino acids. Copyright © 2017 John Wiley & Sons, Ltd.

Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.

PubMed

Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C

2007-07-26

Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.

Organic nanostructures of thermally activated delayed fluorescent emitters with enhanced intersystem crossing as novel metal-free photosensitizers.

PubMed

Zhang, Jinfeng; Chen, Wencheng; Chen, Rui; Liu, Xiao-Ke; Xiong, Yuan; Kershaw, Stephen V; Rogach, Andrey L; Adachi, Chihaya; Zhang, Xiaohong; Lee, Chun-Sing

2016-09-27

We applied organic nanostructures based on thermally activated delayed fluorescent (TADF) emitters for singlet oxygen generation. Due to the extremely small energy gaps between the excited singlet states (S 1 ) and triplet states (T 1 ) of these heavy-metal-free organic nanostructures, intersystem conversion between S 1 and T 1 can occur easily. This strategy also works well for exciplex-type TADF emitters prepared by mixing suitable donors and acceptors which have no TADF characteristics themselves.

Refining the reaction mechanism of O2 towards its co-substrate in cofactor-free dioxygenases

PubMed Central

2016-01-01

Cofactor-less oxygenases perform challenging catalytic reactions between singlet co-substrates and triplet oxygen, in spite of apparently violating the spin-conservation rule. In 1-H-3-hydroxy-4-oxoquinaldine-2,4-dioxygenase, the active site has been suggested by quantum chemical computations to fine tune triplet oxygen reactivity, allowing it to interact rapidly with its singlet substrate without the need for spin inversion, and in urate oxidase the reaction is thought to proceed through electron transfer from the deprotonated substrate to an aminoacid sidechain, which then feeds the electron to the oxygen molecule. In this work, we perform additional quantum chemical computations on these two systems to elucidate several intriguing features unaddressed by previous workers. These computations establish that in both enzymes the reaction proceeds through direct electron transfer from co-substrate to O2 followed by radical recombination, instead of minimum-energy crossing points between singlet and triplet potential energy surfaces without formal electron transfer. The active site does not affect the reactivity of oxygen directly but is crucial for the generation of the deprotonated form of the co-substrates, which have redox potentials far below those of their protonated forms and therefore may transfer electrons to oxygen without sizeable thermodynamic barriers. This mechanism seems to be shared by most cofactor-less oxidases studied so far. PMID:28028471

Refining the reaction mechanism of O2 towards its co-substrate in cofactor-free dioxygenases.

PubMed

Silva, Pedro J

2016-01-01

Cofactor-less oxygenases perform challenging catalytic reactions between singlet co-substrates and triplet oxygen, in spite of apparently violating the spin-conservation rule. In 1- H -3-hydroxy-4-oxoquinaldine-2,4-dioxygenase, the active site has been suggested by quantum chemical computations to fine tune triplet oxygen reactivity, allowing it to interact rapidly with its singlet substrate without the need for spin inversion, and in urate oxidase the reaction is thought to proceed through electron transfer from the deprotonated substrate to an aminoacid sidechain, which then feeds the electron to the oxygen molecule. In this work, we perform additional quantum chemical computations on these two systems to elucidate several intriguing features unaddressed by previous workers. These computations establish that in both enzymes the reaction proceeds through direct electron transfer from co-substrate to O 2 followed by radical recombination, instead of minimum-energy crossing points between singlet and triplet potential energy surfaces without formal electron transfer. The active site does not affect the reactivity of oxygen directly but is crucial for the generation of the deprotonated form of the co-substrates, which have redox potentials far below those of their protonated forms and therefore may transfer electrons to oxygen without sizeable thermodynamic barriers. This mechanism seems to be shared by most cofactor-less oxidases studied so far.

Laser controlled singlet oxygen generation in mitochondria to promote mitochondrial DNA replication in vitro.

PubMed

Zhou, Xin; Wang, Yupei; Si, Jing; Zhou, Rong; Gan, Lu; Di, Cuixia; Xie, Yi; Zhang, Hong

2015-11-18

Reports have shown that a certain level of reactive oxygen species (ROS) can promote mitochondrial DNA (mtDNA) replication. However, it is unclear whether it is the mitochondrial ROS that stimulate mtDNA replication and this requires further investigation. Here we employed a photodynamic system to achieve controlled mitochondrial singlet oxygen ((1)O2) generation. HeLa cells incubated with 5-aminolevulinic acid (ALA) were exposed to laser irradiation to induce (1)O2 generation within mitochondria. Increased mtDNA copy number was detected after low doses of 630 nm laser light in ALA-treated cells. The stimulated mtDNA replication was directly linked to mitochondrial (1)O2 generation, as verified using specific ROS scavengers. The stimulated mtDNA replication was regulated by mitochondrial transcription factor A (TFAM) and mtDNA polymerase γ. MtDNA control region modifications were induced by (1)O2 generation in mitochondria. A marked increase in 8-Oxoguanine (8-oxoG) level was detected in ALA-treated cells after irradiation. HeLa cell growth stimulation and G1-S cell cycle transition were also observed after laser irradiation in ALA-treated cells. These cellular responses could be due to a second wave of ROS generation detected in mitochondria. In summary, we describe a controllable method of inducing mtDNA replication in vitro.

Singlet oxygen in the coupled photochemical and biochemical oxidation of dissolved organic matter.

PubMed

Cory, Rose M; McNeill, Kristopher; Cotner, James P; Amado, Andre; Purcell, Jeremiah M; Marshall, Alan G

2010-05-15

Dissolved organic matter (DOM) is a significant (>700 Pg) global C pool. Transport of terrestrial DOM to the inland waters and coastal zones represents the largest flux of reduced C from land to water (215 Tg yr(-1)) (Meybeck, M. Am. J. Sci. 1983, 282, 401-450). Oxidation of DOM by interdependent photochemical and biochemical processes largely controls the fate of DOM entering surface waters. Reactive oxygen species (ROS) have been hypothesized to play a significant role in the photooxidation of DOM, because they may oxidize the fraction of DOM that is inaccessible to direct photochemical degradation by sunlight. We followed the effects of photochemically produced singlet oxygen ((1)O(2)) on DOM by mass spectrometry with (18)O-labeled oxygen, to understand how (1)O(2)-mediated transformations of DOM may lead to altered DOM bioavailability. The photochemical oxygen uptake by DOM attributed to (1)O(2) increased with DOM concentration, yet it remained a minority contributor to photochemical oxygen uptake even at very high DOM concentrations. When DOM samples were exposed to (1)O(2)-generating conditions (Rose Bengal and visible light), increases were observed in DOM constituents with higher oxygen content and release of H(2)O(2) was detected. Differential effects of H(2)O(2) and (1)O(2)-treated DOM showed that (1)O(2)-treated DOM led to slower bacterial growth rates relative to unmodified DOM. Results of this study suggested that the net effect of the reactions between singlet oxygen and DOM may be production of partially oxidized substrates with correspondingly lower potential biological energy yield.

Singlet oxygen luminescence kinetics under PDI relevant conditions of pathogenic dermatophytes and molds.

PubMed

Bornhütter, Tobias; Shamali, Nedaa; Saltsman, Irena; Mahammed, Atif; Gross, Zeev; Däschlein, Georg; Röder, Beate

2018-01-01

A treatment of onychomycosis using the photodynamic effect would be a favorable alternative to currently used antimycotic drugs. This study should be considered as a first step towards development and control of an efficient photodynamic inactivation of onychomycosis causative pathogens. Here, we evaluate the usage of time-resolved 2D singlet oxygen luminescence detection in combination with 2D fluorescence scanning as a tool to understand the behavior of the photosensitizer when applied to fungi on Petri dishes. To investigate the interaction of photosensitizer with fungi in various concentrations and in different stages of live, a photodynamic inactivation was avoided by keeping the samples in darkness. Scans of singlet oxygen luminescence and photosensitizer fluorescence were performed over a period of 24days. Two different photosensitizer, a cationic porphyrin and cationic corrole and two fungi strains, the dermatophyte Trichophyton rubrum and the mold Scopulariopsis brevicaulis, were investigated in this study. The two-dimensional correlation of photosensitizer fluorescence and singlet oxygen luminescence revealed differences in the diffusion of both photosensitizer. Even though the singlet oxygen luminescence was quenched with increasing growth of fungi, it was found that the kinetics of singlet oxygen luminescence could be detected on Petri dishes for both photosensitizers and both fungi strains for up to seven days. Copyright © 2017 Elsevier B.V. All rights reserved.

Intracellular singlet oxygen photosensitizers: on the road to solving the problems of sensitizer degradation, bleaching and relocalization.

PubMed

da Silva, Elsa F F; Pimenta, Frederico M; Pedersen, Brian W; Blaikie, Frances H; Bosio, Gabriela N; Breitenbach, Thomas; Westberg, Michael; Bregnhøj, Mikkel; Etzerodt, Michael; Arnaut, Luis G; Ogilby, Peter R

2016-02-01

Selected singlet oxygen photosensitizers have been examined from the perspective of obtaining a molecule that is sufficiently stable under conditions currently employed to study singlet oxygen behavior in single mammalian cells. Reasonable predictions about intracellular sensitizer stability can be made based on solution phase experiments that approximate the intracellular environment (e.g., solutions containing proteins). Nevertheless, attempts to construct a stable sensitizer based solely on the expected reactivity of a given functional group with singlet oxygen are generally not sufficient for experiments in cells; it is difficult to construct a suitable chromophore that is impervious to all of the secondary and/or competing degradative processes that are present in the intracellular environment. On the other hand, prospects are reasonably positive when one considers the use of a sensitizer encapsulated in a specific protein; the local environment of the chromophore is controlled, degradation as a consequence of bimolecular reactions can be mitigated, and genetic engineering can be used to localize the encapsulated sensitizer in a given cellular domain. Also, the option of directly exciting oxygen in sensitizer-free experiments provides a useful complementary tool. These latter systems bode well with respect to obtaining more accurate control of the "dose" of singlet oxygen used to perturb a cell; a parameter that currently limits mechanistic studies of singlet-oxygen-mediated cell signaling.

Study of factors influencing the effective delivery of O2(1delta) into the resonator of the oxygen-iodine laser

NASA Astrophysics Data System (ADS)

Krukowski, I. M.; Halin, A. L.

1994-08-01

Experimental studies have been performed on the processes: chlorine utilization in the bubbler type singlet oxygen generator, the quenching of O2(1(Delta) ) in the OIL path, the propagation of the gas mixture O2 + O2 (1(Delta) ) + H2O throughout forward flow-type water vapor trap.

One- and two-photon photosensitized singlet oxygen production: characterization of aromatic ketones as sensitizer standards.

PubMed

Arnbjerg, Jacob; Paterson, Martin J; Nielsen, Christian B; Jørgensen, Mikkel; Christiansen, Ove; Ogilby, Peter R

2007-07-05

Singlet molecular oxygen, O2(a1Deltag), can be efficiently produced in a photosensitized process using either one- or two-photon irradiation. The aromatic ketone 1-phenalenone (PN) is an established one-photon singlet oxygen sensitizer with many desirable attributes for use as a standard. In the present work, photophysical properties of two other aromatic ketones, pyrene-1,6-dione (PD) and benzo[cd]pyren-5-one (BP), are reported and compared to those of PN. Both PD and BP sensitize the production of singlet oxygen with near unit quantum efficiency in a nonpolar (toluene) and a polar (acetonitrile) solvent. With their more extensive pi networks, the one-photon absorption spectra for PD and BP extend out to longer wavelengths than that for PN, thus providing increased flexibility for sensitizer excitation over the range approximately 300-520 nm. Moreover, PD and BP have much larger two-photon absorption cross sections than PN over the range 655-840 nm which, in turn, results in amounts of singlet oxygen that are readily detected in optical experiments. One- and two-photon absorption spectra of PD and BP obtained using high-level calculations model the salient features of the experimental data well. In particular, the ramifications of molecular symmetry are clearly reflected in both the experimental and calculated spectra. The use of PD and BP as standards for both the one- and two-photon photosensitized production of singlet oxygen is expected to facilitate the development of new sensitizers for application in singlet-oxygen-based imaging experiments.

Cold atmospheric-pressure plasma induces DNA-protein crosslinks through protein oxidation.

PubMed

Guo, Li; Zhao, Yiming; Liu, Dingxin; Liu, Zhichao; Chen, Chen; Xu, Ruobing; Tian, Miao; Wang, Xiaohua; Chen, Hailan; Kong, Michael G

2018-05-03

Reactive oxygen and nitrogen species (ROS and RNS) generated by cold atmospheric-pressure plasma could damage genomic DNA, although the precise type of these DNA damage induced by plasma are poorly characterized. Understanding plasma-induced DNA damage will help to elucidate the biological effect of plasma and guide the application of plasma in ROS-based therapy. In this study, it was shown that ROS and RNS generated by physical plasma could efficiently induce DNA-protein crosslinks (DPCs) in bacteria, yeast, and human cells. An in vitro assay showed that plasma treatment resulted in the formation of covalent DPCs by activating proteins to crosslink with DNA. Mass spectrometry and hydroperoxide analysis detected oxidation products induced by plasma. DPC formation were alleviated by singlet oxygen scavenger, demonstrating the importance of singlet oxygen in this process. These results suggested the roles of DPC formation in DNA damage induced by plasma, which could improve the understanding of the biological effect of plasma and help to develop a new strategy in plasma-based therapy including infection and cancer therapy.

Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity.

PubMed

Dabrzalska, Monika; Janaszewska, Anna; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

2017-02-23

The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer-methylene blue (MB). As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS) generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an) was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

Computed Regioselectivity and Conjectured Biological Activity of Ene Reactions of Singlet Oxygen with the Natural Product Hyperforin.

PubMed

Abramova, Inna; Rudshteyn, Benjamin; Liebman, Joel F; Greer, Alexander

2017-03-01

Hyperforin is a constituent of St. John's wort and coexists with the singlet oxygen sensitizer hypericin. Density functional theory, molecular mechanics and Connolly surface calculations show that accessibility in the singlet oxygen "ene" reaction favors the hyperforin "southwest" and "southeast" prenyl (2-methyl-2-butenyl) groups over the northern prenyl groups. While the southern part of hyperforin is initially more susceptible to oxidation, up to 4 "ene" reactions of singlet oxygen can take place. Computational results assist in predicting the fate of adjacent hydroperoxides in hyperforin, where the loss of hydrogen atoms may lead to the formation of a hydrotrioxide and a carbonyl instead of a Russell reaction. © 2017 The American Society of Photobiology.

A prototype of an electric-discharge gas flow oxygen−iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vagin, N. P.; Ionin, A. A., E-mail: aion@sci.lebedev.ru; Kochetov, I. V.

The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O{sub 2}: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions,more » volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as ~100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to ~220–230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen−iodine laser based on a slab cryogenic RF discharge.« less

Effect of intracellular photosensitized singlet oxygen production on the electrophysiological properties of cultured rat hippocampal neurons.

PubMed

Breitenbach, Thomas; Ogilby, Peter R; Lambert, John D C

2010-12-01

Whole-cell patch-clamp recordings from single cultured mammalian neurons have been used to provide insight into early membrane-dependent events that result upon the intracellular photosensitized production of singlet molecular oxygen, O(2)(a(1)Δ(g)). The singlet oxygen sensitizers used, pyropheophorbide a (PPa) and protoporphyrin IX (PpIX), locate mainly in cell membranes and mitochondria, respectively. Irradiation of these sensitizers altered both passive and dynamic electrophysiological properties of the neurons in a dose-dependent manner, though the response threshold was much lower with PPa than with PpIX. In particular, notable decreases were observed in the rising and falling rates of action potentials and, at higher light fluences, plateau potentials consistent with activation of Ca(2+) channels also developed. The data suggest that singlet oxygen production specifically influences Na(+), K(+) and Ca(2+) ionophores in the cell membrane. Upon terminating sensitizer irradiation, responses evoked by PPa stabilized immediately whereas those evoked by PpIX continued to develop. These data are consistent with a spatially-resolved sphere of intracellular singlet oxygen activity. While the response to PPa irradiation appears to be membrane specific, the response to PpIX irradiation appears to be systemic and possibly part of a cascade of apoptotic events. These results should contribute to a better understanding of membrane-dependent events pertinent to cell death mediated by singlet oxygen.

Rational Design of Emissive NIR-Absorbing Chromophores: Rh(III) Porphyrin-Aza-BODIPY Conjugates with Orthogonal Metal-Carbon Bonds.

PubMed

Zhou, Jinfeng; Gai, Lizhi; Zhou, Zhikuan; Yang, Wu; Mack, John; Xu, Kejing; Zhao, Jianzhang; Zhao, Yue; Qiu, Hailin; Chan, Kin Shing; Shen, Zhen

2016-09-05

The facile synthesis of Group 9 Rh(III) porphyrin-aza-BODIPY conjugates that are linked through an orthogonal Rh-C(aryl) bond is reported. The conjugates combine the advantages of the near-IR (NIR) absorption and intense fluorescence of aza-BODIPY dyes with the long-lived triplet states of transition metal rhodium porphyrins. Only one emission peak centered at about 720 nm is observed, irrespective of the excitation wavelength, demonstrating that the conjugates act as unique molecules rather than as dyads. The generation of a locally excited (LE) state with intramolecular charge-transfer (ICT) character has been demonstrated by solvatochromic effects in the photophysical properties, singlet oxygen quantum yields in polar solvents, and by the results of density functional theory (DFT) calculations. In nonpolar solvents, the Rh(III) conjugates exhibit strong aza-BODIPY-centered fluorescence at around 720 nm (ΦF =17-34 %), and negligible singlet oxygen generation. In polar solvents, enhancements of the singlet-oxygen quantum yield (ΦΔ =19-27 %, λex =690 nm) have been observed. Nanosecond pulsed time-resolved absorption spectroscopy confirms that relatively long-lived triplet excited states are formed. The synthetic methodology outlined herein provides a useful strategy for the assembly of functional materials that are highly desirable for a wide range of applications in material science and biomedical fields. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trap formation and energy transfer in pheophorbide a-DAB-dendrimers and pyropheophorbide a-fullerene C 60 hexaadduct molecular systems

NASA Astrophysics Data System (ADS)

Röder, Beate; Ermilov, Eugeny A.; Hackbarth, Steffen; Helmreich, Matthias; Jux, Norbert

2006-04-01

The photophysical properties of DAB-dendrimers from 1 st to 4 th generation as well as Diaminohexane - all substituted with the in maximum achievable quantity of pheophorbide a (Pheo) molecules were studied in comparison with a novel hexapyropheophorbide a - fullerene hexaadduct (FHP6) and a fullerene [6:0]-hexaadduct which carries twelve pyropheophorbide a units (FHP12) using both steady-state and time-resolved spectroscopic methods. It was found that neighboring dye molecules covalently linked to one DAB- or fullerene moiety due to the length and high flexibility of carbon chains could stack with each other. This structural property is the reason for the possibility of formation different types of energy traps, which were resolved experimentally. The dipole-dipole resonance Förster energy transfer between the dye molecules coupled to one complex caused a very fast and efficient delivery of the excitation to a trap. As result the fluorescence as well as the singlet oxygen quantum yields of the different complexes were reduced with increasing number of dye molecules per complex. Nevertheless in every case the singlet oxygen generation was less influenced then the fluorescence quantum yield, exposing the complex to a non-negligible amount of excited oxygen in the singlet state. While the fullerene complexes turned out to be stable under these conditions, the DAB-dendrimer-backbones were completely fragmented to small rudiments carrying just one or a small number of dye molecules.

Singlet oxygen-dependent translational control in the tigrina-d.12 mutant of barley.

PubMed

Khandal, Dhriti; Samol, Iga; Buhr, Frank; Pollmann, Stephan; Schmidt, Holger; Clemens, Stephan; Reinbothe, Steffen; Reinbothe, Christiane

2009-08-04

The tigrina (tig)-d.12 mutant of barley is impaired in the negative control limiting excess protochlorophyllide (Pchlide) accumulation in the dark. Upon illumination, Pchlide operates as photosensitizer and triggers singlet oxygen production and cell death. Here, we show that both Pchlide and singlet oxygen operate as signals that control gene expression and metabolite accumulation in tig-d.12 plants. In vivo labeling, Northern blotting, polysome profiling, and protein gel blot analyses revealed a selective suppression of synthesis of the small and large subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (RBCSs and RBCLs), the major light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCB2), as well as other chlorophyll-binding proteins, in response to singlet oxygen. In part, these effects were caused by an arrest in translation initiation of photosynthetic transcripts at 80S cytoplasmic ribosomes. The observed changes in translation correlated with a decline in the phosphorylation level of ribosomal protein S6. At later stages, ribosome dissociation occurred. Together, our results identify translation as a major target of singlet oxygen-dependent growth control and cell death in higher plants.

Photosensitized singlet oxygen generation and detection: Recent advances and future perspectives in cancer photodynamic therapy.

PubMed

Li, Buhong; Lin, Lisheng; Lin, Huiyun; Wilson, Brian C

2016-12-01

Photodynamic therapy (PDT) uses photosensitizers and visible light in combination with molecular oxygen to produce reactive oxygen species (ROS) that kill malignant cells by apoptosis and/or necrosis, shut down the tumor microvasculature and stimulate the host immune system. The excited singlet state of oxygen ( 1 O 2 ) is recognized to be the main cytotoxic ROS generated during PDT for the majority of photosensitizers used clinically and for many investigational new agents, so that maximizing its production within tumor cells and tissues can improve the therapeutic response, and several emerging and novel approaches for this are summarized. Quantitative techniques for 1 O 2 production measurement during photosensitization are also of immense importance of value for both preclinical research and future clinical practice. In this review, emerging strategies for enhanced photosensitized 1 O 2 generation are introduced, while recent advances in direct detection and imaging of 1 O 2 luminescence are summarized. In addition, the correlation between cumulative 1 O 2 luminescence and PDT efficiency will be highlighted. Meanwhile, the validation of 1 O 2 luminescence dosimetry for PDT application is also considered. This review concludes with a discussion on future demands of 1 O 2 luminescence detection for PDT dosimetry, with particular emphasis on clinical translation. Eye-catching color image for graphical abstract. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unraveling the enhanced photocatalytic activity and phototoxicity of ZnO/metal hybrid nanostructures from generation of reactive oxygen species and charge carriers.

PubMed

He, Weiwei; Wu, Haohao; Wamer, Wayne G; Kim, Hyun-Kyung; Zheng, Jiwen; Jia, Huimin; Zheng, Zhi; Yin, Jun-Jie

2014-09-10

An effective way for promoting photocatalytic activity of a semiconductor is deposition of noble metal nanoparticles (NPs) onto it. In this paper, we deposited Ag and Pd onto ZnO NPs to form ZnO/Ag and ZnO/Pd hybrid nanostructures. It was found that both Ag and Pd nanocomponents can greatly enhance the photocatalytic activity and phototoxicity of ZnO toward human skin cells. Using electron spin resonance spectroscopy with spin trapping and spin labeling techniques, we observed that either deposition of Ag or Pd resulted in a significant increase in photogenerated electrons and holes and production of reactive oxygen species including hydroxyl radicals, superoxide, and singlet oxygen. We compared the enhancing effects of Ag and Pd and found that Pd is more effective than Ag in promoting the generation of hydroxyl radicals and holes and the photocatalytic activity of ZnO. Conversely, Ag is more effective than Pd in enhancing electron transfer and the generation of superoxide and singlet oxygen. The mechanism underlying the differences in the effects of Ag and Pd may be related to differences in Fermi levels for Ag and Pd and band bending accompanied by effects on Schottky barriers. The results of these studies provide information valuable for designing hybrid nanomaterials having photocatalytic and photobiological activities useful for applications such as water purification and formulation of antibacterial products.

Singlet oxygen production by chloroperoxidase-hydrogen peroxide-halide systems.

PubMed

Kanofsky, J R

1984-05-10

Singlet oxygen production in the chloroperoxidase-hydrogen peroxide-halide system was studied using 1268 nm chemiluminescence. With chloride or bromide ions, singlet oxygen is produced by the mechanism (formula; see text) (formula; see text) where X- is chloride or bromide ion. Under conditions where there is high enzyme activity and when Reaction B is fast relative to Reaction A, singlet oxygen is produced in near stoichiometric amounts. In contrast, when Reaction A is fast relative to Reaction B, oxidized halogen species (chlorine and hypochlorous acid for chloride ion; bromide, tribromide ion, and hypobromous acid for bromide ion) are the principle reaction products. With iodide ion, no 1268 nm chemiluminescence was detected. Past studies have shown that iodine and iodate ion are the major end products of this system.

Temporal profile of the singlet oxygen emission endogenously produced by photosystem II reaction centre in an aqueous buffer.

PubMed

Li, Heng; Melø, Thor Bernt; Arellano, Juan B; Razi Naqvi, K

2012-04-01

The temporal profile of the phosphorescence of singlet oxygen endogenously photosensitized by photosystem II (PSII) reaction centre (RC) in an aqueous buffer has been recorded using laser excitation and a near infrared photomultiplier tube. A weak emission signal was discernible, and could be fitted to the functional form a[exp(-t/τ(2) - exp(-t/τ(1)], with a > 0 and τ(2) > τ(1). The value of τ(2) decreased from 11.6 ± 0.5 μs under aerobic conditions to 4.1 ± 0.2 μs in oxygen-saturated samples, due to enhanced bimolecular quenching of the donor triplet by oxygen, whereas that of τ(1), identifiable with the lifetime of singlet oxygen, was close to 3 μs in both cases. Extrapolations based on the low amplitude of the emission signal of singlet oxygen formed by PSII RC in the aqueous buffer and the expected values of τ(1) and τ(2) in chloroplasts indicate that attempts to analyse the temporal profile of singlet oxygen in chloroplasts are unlikely to be rewarded with success without a significant advance in the sensitivity of the detection equipment. © Springer Science+Business Media B.V. 2012

Singlet Oxygen in Aqueous Solution: A Lecture Demonstration

ERIC Educational Resources Information Center

Shakhashiri, Bassam Z.; Williams, Lloyd G.

1976-01-01

Describes a demonstration that illustrates the red chemiluminescence due to singlet molecular oxygen that can be observed when aqueous solutions of hypochlorite ion and hydrogen peroxide are mixed. (MLH)

Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

PubMed Central

Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

2015-01-01

Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetramethyl-benzidine (TMB), as well as, analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes’ activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC towards oxidation of TMB is very high and shows direct two-electrons oxidation when the surface of PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent but only with appropriate drug delivery system. PMID:25886644

Observation of the death process of cancer cells killed through surface plasmon resonance of gold nanoring with optical coherence tomography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chen, Shih-Yang; He, Yulu; Hsieh, Cheng-Che; Hua, Wei-Hsiang; Low, Meng Chun; Tsai, Meng-Tsan; Kiang, Yean-Woei; Yang, Chih-Chung

2017-02-01

The use of a high-resolution optical coherence tomography (OCT) system with the operation wavelength around 800 nm to scan SCC4 cancer cells under different laser illumination conditions is demonstrated. The cancer cells are incubated with Au nanorings (NRIs), which are linked with photosensitizer, AlPcS, for them to be up-taken by the cells. Two Au NRI samples of different geometries for inducing localized surface plasmon (LSP) resonance around 1310 and 1064 nm are used. Four different lasers are utilized for illuminating the cells under OCT scanning, including 1310-nm continuous (cw) laser, 1064-nm cw laser, 1064-nm femtosecond (fs) laser, and 660-nm cw laser. The 1310- and 1064-nm cw lasers mainly produce the photothermal effect through the LSP resonance of Au NRIs for damaging the observed cells. Besides the photothermal effect, the 1064-nm fs laser can produce strong two-photon absorption through the assistance of the LSP resonance of Au NRI for exciting AlPcS to effectively generate singlet oxygen and damage the observed cells. The 660-nm laser can excite AlPcS through single-photon absorption for generating singlet oxygen and damaging the observed cells. With the photothermal effect, the observed cells can be killed through the process of necrosis. Through the generation of singlet oxygen, the cell membrane can be preserved and the interior substances are solidified to become a hard body of strong scattering. In this situation, the cells are killed through the apoptosis process. Illuminated by the 660-nm cw laser, a process of interior substance escape is observed through high-speed OCT scanning.

Reactions of singlet oxygen with pine pollen.

NASA Technical Reports Server (NTRS)

Dowty, B.; Laseter, J. L.; Griffin, G. W.; Politzer, I. R.; Walkinshaw, C. H.

1973-01-01

A study was initiated to determine whether viable atmospheric particles such as plant pollens and fungal spores containing unsaturated lipids can interact with singlet oxygen to give oxygenated products that are potentially toxic. The results obtained confirm that surface and near surface components of common viable particulate matter in the atmosphere may be subject to rapid oxidation by singlet oxygen, leading to products which are probably allylic hydroperoxides. In connection with increasing atmospheric pollution, it is important to note that materials toxic to mammalian lung tissue may be oxidatively produced on the surfaces of viable particulate matter.

Li-air batteries: Importance of singlet oxygen

NASA Astrophysics Data System (ADS)

Luntz, Alan C.; McCloskey, Bryan D.

2017-04-01

The deployment of Li-air batteries is hindered by severe parasitic reactions during battery cycling. Now, the reactive singlet oxygen intermediate is shown to substantially contribute to electrode and electrolyte degradation.

Influence of clay minerals on curcumin properties: Stability and singlet oxygen generation

NASA Astrophysics Data System (ADS)

Gonçalves, Joyce L. S.; Valandro, Silvano R.; Poli, Alessandra L.; Schmitt, Carla C.

2017-09-01

Curcumin (CUR) has showed promising photophysical properties regarding to biological and chemical sciences. However, the main barrier for those applications are their low solubility and stability in aqueous solution. The effects of two different clay minerals, the montmorillonite (SWy-2) and the Laponite RD (Lap) nanoclay, on the stabilization of Curcumin were investigated. Their effects were compared with two well-established environments (acidic and neutral aqueous media). CUR/clay hybrids were prepared using a simple and fast method, where CUR solution was added into clay suspensions, to obtain well dispersed hybrids in water. The degradation process of CUR and CUR/clays hybrids was investigated using UV-Vis spectroscopic. For both studied hybrids, the CUR degradation process was suppressed by the presence of the clay particles. Furthermore, the Lap showed a great stabilization effect than SWy-2. This behavior was due to the smaller particle size and higher exfoliation ability of Lap, providing a large surface for CUR adsorption compared to SWy-2. The degradation process of CUR solutions and CUR/clay hybrids was also studied in the presence of light. CUR photodegradation process was faster not only in the aqueous solution but also in the clay suspension compared to those studied in the dark. The presence of clay particles accelerated the photodegradation of CUR due to the products formation in the reactions between CUR and oxygen radicals. Our results showed that the singlet oxygen quantum yield (ΦΔ) of CUR were about 59% higher in the clay suspensions than CUR in aqueous solution. Therefore, the formation of CUR/clay hybrids, in particularly with Lap, suppressed the degradation in absence light of CUR and increased the singlet oxygen generation, which makes this hybrids of CUR/clay a promising material to enlarge the application of CUR in the biological sciences.

High throughput photo-oxidations in a packed bed reactor system.

PubMed

Kong, Caleb J; Fisher, Daniel; Desai, Bimbisar K; Yang, Yuan; Ahmad, Saeed; Belecki, Katherine; Gupton, B Frank

2017-12-01

The efficiency gains produced by continuous-flow systems in conducting photochemical transformations have been extensively demonstrated. Recently, these systems have been used in developing safe and efficient methods for photo-oxidations using singlet oxygen generated by photosensitizers. Much of the previous work has focused on the use of homogeneous photocatalysts. The development of a unique, packed-bed photoreactor system using immobilized rose bengal expands these capabilities as this robust photocatalyst allows access to and elaboration from these highly useful building blocks without the need for further purification. With this platform we were able to demonstrate a wide scope of singlet oxygen ene, [4+2] cycloadditions and heteroatom oxidations. Furthermore, we applied this method as a strategic element in the synthesis of the high-volume antimalarial artemisinin. Copyright © 2017. Published by Elsevier Ltd.

Nanoscale metal-organic frameworks for photodynamic therapy and cancer immunotherapy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lin, Wenbin

2017-02-01

Photodynamic therapy (PDT) is an effective anticancer procedure that relies on tumor localization of a photosensitizer followed by light activation to generate cytotoxic reactive oxygen species. We recently reported the rational design of a Hf-porphyrin nanoscale metal-organic framework, DBP-UiO, as an exceptionally effective photosensitizer for PDT of resistant head and neck cancer. DBP-UiO efficiently generates singlet oxygen owing to site isolation of porphyrin ligands, enhanced intersystem crossing by heavy Hf centers, and facile singlet oxygen diffusion through porous DBP-UiO nanoplates. Consequently, DBP-UiO displayed greatly enhanced PDT efficacy both in vitro and in vivo, leading to complete tumor eradication in half of the mice receiving a single DBP-UiO dose and a single light exposure. The photophysical properties of DBP-UiO are however not optimum with the lowest energy absorption at 634 nm and a relatively small extinction coefficient of 2200 M-1·cm-1. We recently designed a chlorin-based NMOF, DBC-UiO, with much improved photophysical properties and PDT efficacy in two colon cancer mouse models. Reduction of the DBP ligands in DBP-UiO to the DBC ligands in DBC-UiO led to a 13 nm red-shift and an 11-fold extinction coefficient increase of the lowest energy Q-band. While inheriting the crystallinity, stability, porosity, and nanoplate morphology of DBP-UiO, DBC-UiO sensitizes more efficient singlet oxygen generation and exhibits much enhanced photodynamic therapy (PDT) efficacy on two colon cancer mouse models as a result of its improved photophysical properties. Both apoptosis and immunogenic cell death contributed to cancer cell-killing in DBC-UiO induced PDT. Our work has thus demonstrated that NMOFs represent a new class of highly potent PDT agents and hold great promise in treating resistant cancers in the clinic.

Chlorine measurement in the jet singlet oxygen generator considering the effects of the droplets.

PubMed

Goodarzi, Mohamad S; Saghafifar, Hossein

2016-09-01

A new method is presented to measure chlorine concentration more accurately than conventional method in exhaust gases of a jet-type singlet oxygen generator. One problem in this measurement is the existence of micrometer-sized droplets. In this article, an empirical method is reported to eliminate the effects of the droplets. Two wavelengths from a fiber coupled LED are adopted and the measurement is made on both selected wavelengths. Chlorine is measured by the two-wavelength more accurately than the one-wavelength method by eliminating the droplet term in the equations. This method is validated without the basic hydrogen peroxide injection in the reactor. In this case, a pressure meter value in the diagnostic cell is compared with the optically calculated pressure, which is obtained by the one-wavelength and the two-wavelength methods. It is found that chlorine measurement by the two-wavelength method and pressure meter is nearly the same, while the one-wavelength method has a significant error due to the droplets.

Synthesis, characterization and investigation of the photophysical and photochemical properties of highly soluble novel metal-free, zinc(II), and indium(III) phthalocyanines substituted with 2,3,6-trimethylphenoxy moieties.

PubMed

Gürel, Ekrem; Pişkin, Mehmet; Altun, Selçuk; Odabaş, Zafer; Durmuş, Mahmut

2015-04-07

This work presents the synthesis and characterization of metal-free, zinc(II), and indium(III)acetate phthalocyanines substituted with 2,3,6-trimethylphenoxy groups at the peripheral and non-peripheral positions. The photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties of these novel phthalocyanines and unsubstituted zinc(II) and indium(III)acetate phthalocyanines were investigated in dimethylformamide solution. The effects of the types of substituents and their positions and the variety of central metal ions on the phthalocyanine core on their spectroscopic, photophysical and photochemical properties were also determined. The studied 2,3,6-trimethylphenoxy substituted metal-free, zinc(II) and indium(III)acetate phthalocyanines especially indium(III)acetate derivatives exhibited appropriate photophysical and photochemical properties such as high singlet oxygen generation and these phthalocyanines can be potential Type II photosensitizers for photodynamic therapy in cancer applications.

Click-electron microscopy for imaging metabolically tagged non-protein biomolecules

PubMed Central

Ngo, John T.; Adams, Stephen R.; Deerinck, Thomas J.; Boassa, Daniela; Rodriguez-Rivera, Frances; Palida, Sakina F.; Bertozzi, Carolyn R.; Ellisman, Mark H.; Tsien, Roger Y.

2016-01-01

Electron microscopy (EM) has long been the main technique to image cell structures with nanometer resolution, but has lagged behind light microscopy in the crucial ability to make specific molecules stand out. Here we introduce “Click-EM,” a labeling technique for correlative light microscopy and EM imaging of non-protein biomolecules. In this approach, metabolic labeling substrates containing bioorthogonal functional groups are provided to cells for incorporation into biopolymers by endogenous biosynthetic machinery. The unique chemical functionality of these analogs is exploited for selective attachment of singlet oxygen-generating fluorescent dyes via bioorthogonal “click chemistry” ligations. Illumination of dye-labeled structures generates singlet oxygen to locally catalyze the polymerization of diaminobenzidine into an osmiophilic reaction product that is readily imaged by EM. We describe the application of Click-EM in imaging metabolically tagged DNA, RNA, and lipids in cultured cells and neurons, and highlight its use in tracking peptidoglycan synthesis in the Gram-positive bacterium Listeria monocytogenes. PMID:27110681

Development of Singlet Oxygen Luminescence Kinetics during the Photodynamic Inactivation of Green Algae.

PubMed

Bornhütter, Tobias; Pohl, Judith; Fischer, Christian; Saltsman, Irena; Mahammed, Atif; Gross, Zeev; Röder, Beate

2016-04-13

Recent studies show the feasibility of photodynamic inactivation of green algae as a vital step towards an effective photodynamic suppression of biofilms by using functionalized surfaces. The investigation of the intrinsic mechanisms of photodynamic inactivation in green algae represents the next step in order to determine optimization parameters. The observation of singlet oxygen luminescence kinetics proved to be a very effective approach towards understanding mechanisms on a cellular level. In this study, the first two-dimensional measurement of singlet oxygen kinetics in phototrophic microorganisms on surfaces during photodynamic inactivation is presented. We established a system of reproducible algae samples on surfaces, incubated with two different cationic, antimicrobial potent photosensitizers. Fluorescence microscopy images indicate that one photosensitizer localizes inside the green algae while the other accumulates along the outer algae cell wall. A newly developed setup allows for the measurement of singlet oxygen luminescence on the green algae sample surfaces over several days. The kinetics of the singlet oxygen luminescence of both photosensitizers show different developments and a distinct change over time, corresponding with the differences in their localization as well as their photosensitization potential. While the complexity of the signal reveals a challenge for the future, this study incontrovertibly marks a crucial, inevitable step in the investigation of photodynamic inactivation of biofilms: it shows the feasibility of using the singlet oxygen luminescence kinetics to investigate photodynamic effects on surfaces and thus opens a field for numerous investigations.

An ab initio mechanism for efficient population of triplet states in cytotoxic sulfur substituted DNA bases: the case of 6-thioguanine.

PubMed

Martínez-Fernández, Lara; González, Leticia; Corral, Inés

2012-02-18

The deactivation mechanism of the cytotoxic 6-thioguanine, the 6-sulfur-substituted analogue of the canonical DNA base, is unveiled by ab initio calculations. Oxygen-by-sulfur substitution leads to efficient population of triplet states-the first step for generating singlet oxygen-which is responsible for its cytotoxicity. This journal is © The Royal Society of Chemistry 2012

Cyanide oxidation by singlet oxygen generated via reaction between H2O2 from cathodic reduction and OCl(-) from anodic oxidation.

PubMed

Tian, Shichao; Li, Yibing; Zeng, Huabin; Guan, Wei; Wang, Yan; Zhao, Xu

2016-11-15

Cyanide is widely present in electroplating wastewater or metallurgical effluents. In the present study, the electrochemical destruction of cyanide with various anode and cathode compositions under alkaline conditions was investigated. The results indicated that the electrochemical system using RuO2/Ti as anode and activated carbon fiber (ACF) as cathode in the presence of sodium chloride was efficient for the cyanide removal. In this system, in situ generation of HClO by anodic oxidation of Cl(-) at RuO2/Ti anode occurred with the H2O2 generation by O2 reduction at ACF cathode. As confirmed by the electron spin resonance technique, the reaction between HClO and H2O2 led to the generation of singlet oxygen, which was responsible for the cyanide removal. Further experiment indicated that the cyanide removal efficiency increased with the increase of the current density or the sodium chloride concentration. Cyanate was identified as main product in the system. Besides, the system exhibited good stability for the cyanide removal, which was beneficial to its practical application. Copyright © 2016. Published by Elsevier Inc.

Supramolecular nanoreactors for intracellular singlet-oxygen sensitization

NASA Astrophysics Data System (ADS)

Swaminathan, Subramani; Fowley, Colin; Thapaliya, Ek Raj; McCaughan, Bridgeen; Tang, Sicheng; Fraix, Aurore; Burjor, Captain; Sortino, Salvatore; Callan, John F.; Raymo, Françisco M.

2015-08-01

An amphiphilic polymer with multiple decyl and oligo(ethylene glycol) chains attached to a common poly(methacrylate) backbone assembles into nanoscaled particles in aqueous environments. Hydrophobic anthracene and borondipyrromethene (BODIPY) chromophores can be co-encapsulated within the self-assembling nanoparticles and transported across hydrophilic media. The reversible character of the noncovalent bonds, holding the supramolecular containers together, permits the exchange of their components with fast kinetics in aqueous solution. Incubation of cervical cancer (HeLA) cells with a mixture of two sets of nanoparticles, pre-loaded independently with anthracene or BODIPY chromophores, results in guest scrambling first and then transport of co-entrapped species to the intracellular space. Alternatively, incubation of cells with the two sets of nanocarriers in consecutive steps permits the sequential transport of the anthracene and BODIPY chromophores across the plasma membrane and only then allows their co-encapsulation within the same supramolecular containers. Both mechanisms position the two sets of chromophores with complementary spectral overlap in close proximity to enable the efficient transfer of energy intracellularly from the anthracene donors to the BODIPY acceptors. In the presence of iodine substituents on the BODIPY platform, intersystem crossing follows energy transfer. The resulting triplet state can transfer energy further to molecular oxygen with the concomitant production of singlet oxygen to induce cell mortality. Furthermore, the donor can be excited with two near-infrared photons simultaneously to permit the photoinduced generation of singlet oxygen intracellularly under illumination conditions compatible with applications in vivo. Thus, these supramolecular strategies to control the excitation dynamics of multichromophoric assemblies in the intracellular environment can evolve into valuable protocols for photodynamic therapy.An amphiphilic polymer with multiple decyl and oligo(ethylene glycol) chains attached to a common poly(methacrylate) backbone assembles into nanoscaled particles in aqueous environments. Hydrophobic anthracene and borondipyrromethene (BODIPY) chromophores can be co-encapsulated within the self-assembling nanoparticles and transported across hydrophilic media. The reversible character of the noncovalent bonds, holding the supramolecular containers together, permits the exchange of their components with fast kinetics in aqueous solution. Incubation of cervical cancer (HeLA) cells with a mixture of two sets of nanoparticles, pre-loaded independently with anthracene or BODIPY chromophores, results in guest scrambling first and then transport of co-entrapped species to the intracellular space. Alternatively, incubation of cells with the two sets of nanocarriers in consecutive steps permits the sequential transport of the anthracene and BODIPY chromophores across the plasma membrane and only then allows their co-encapsulation within the same supramolecular containers. Both mechanisms position the two sets of chromophores with complementary spectral overlap in close proximity to enable the efficient transfer of energy intracellularly from the anthracene donors to the BODIPY acceptors. In the presence of iodine substituents on the BODIPY platform, intersystem crossing follows energy transfer. The resulting triplet state can transfer energy further to molecular oxygen with the concomitant production of singlet oxygen to induce cell mortality. Furthermore, the donor can be excited with two near-infrared photons simultaneously to permit the photoinduced generation of singlet oxygen intracellularly under illumination conditions compatible with applications in vivo. Thus, these supramolecular strategies to control the excitation dynamics of multichromophoric assemblies in the intracellular environment can evolve into valuable protocols for photodynamic therapy. Electronic supplementary information (ESI) available: Experimental procedures; crystallographic data; absorption and emission spectra; temporal absorbance profiles; singlet-oxygen measurements; intracellular fluorescence measurements; viability assays. See DOI: 10.1039/c5nr02672e

Quenching of porous silicon photoluminescence by molecular oxygen and dependence of this phenomenon on storing media and method of preparation of pSi photosensitizer

NASA Astrophysics Data System (ADS)

Balaguer, María; Matveeva, Eugenia

2010-10-01

The quenching of porous silicon photoluminescence (pSi PL) by molecular oxygen has been studied in different storing media in an attempt to clarify the mechanism of the energy transfer from the silicon photosensitizer to the oxygen acceptor. Luminescent materials have been prepared by two methods: electrochemical anodizing and chemical etching. Different structural forms were used: porous layers on silicon wafer and two kinds of differently prepared powder. Dry air and liquid water were employed as storing media; quenching behaviour was under observation until total degradation of quenching properties. Singlet oxygen molecules generation through energy transfer from photoluminescent pSi was the only photosensitizing mechanism observed under dry gas conditions. This PL quenching process was preferentially developed at 760 nm (1.63 eV) that corresponds to the formation of the 1Σ singlet oxygen state. Oxidation of the pSi photosensitizer was the main factor that led to its total deactivation in a time scale of few weeks. Regarding water medium, different photosensitizing behaviour was observed. In watery conditions, two preferred energy levels were found: the one detected in dry gas and another centred at approximately 2.2 eV (550 nm). Formation of reactive oxygen species (ROS) different from singlet oxygen, such as superoxide anion or superoxide radical, can be responsible for the second one. This second quenching process developed gradually after the initial contact of pSi photosensitizer with water and then degraded. The process lasted only several hours. Therefore, functionalization of the pSi photosensitizer is probably required to stabilize its PL and quenching properties in the watery physiological conditions required for biomedical applications.

Singlet oxygen-dependent translational control in the tigrina-d.12 mutant of barley

PubMed Central

Khandal, Dhriti; Samol, Iga; Buhr, Frank; Pollmann, Stephan; Schmidt, Holger; Clemens, Stephan; Reinbothe, Steffen; Reinbothe, Christiane

2009-01-01

The tigrina (tig)-d.12 mutant of barley is impaired in the negative control limiting excess protochlorophyllide (Pchlide) accumulation in the dark. Upon illumination, Pchlide operates as photosensitizer and triggers singlet oxygen production and cell death. Here, we show that both Pchlide and singlet oxygen operate as signals that control gene expression and metabolite accumulation in tig-d.12 plants. In vivo labeling, Northern blotting, polysome profiling, and protein gel blot analyses revealed a selective suppression of synthesis of the small and large subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (RBCSs and RBCLs), the major light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCB2), as well as other chlorophyll-binding proteins, in response to singlet oxygen. In part, these effects were caused by an arrest in translation initiation of photosynthetic transcripts at 80S cytoplasmic ribosomes. The observed changes in translation correlated with a decline in the phosphorylation level of ribosomal protein S6. At later stages, ribosome dissociation occurred. Together, our results identify translation as a major target of singlet oxygen-dependent growth control and cell death in higher plants. PMID:19620736

Effect of dye localization and self-interactions on the photosensitized generation of singlet oxygen by rose bengal bound to bovine serum albumin.

PubMed

Turbay, María Beatriz Espeche; Rey, Valentina; Argañaraz, Natalia M; Morán Vieyra, Faustino E; Aspée, Alexis; Lissi, Eduardo A; Borsarelli, Claudio D

2014-12-01

The spectroscopic and photophysical properties of rose bengal (RB) encased in bovine serum albumin (BSA) have been examined to evaluate the photosensitized generation of singlet molecular oxygen ((1)O2). The results show that RB photophysical and photosensitizing properties are highly modulated by the average number of dye molecules per protein (n). At n ≪ 1, the dye molecule is tightly located into the hydrophobic nanocavity site I of the BSA molecule with a binding constant Kb = 0.15 ± 0.01 μM(-1). The interaction with surrounding amino acids induces heterogeneous decay of both singlet and triplet excited states of RB and partially reduce its triplet quantum yield as compared with that in buffer solution. However, despite of the diffusive barrier imposed by the protein nanocavity to (3)O2, the quenching of (3)RB(∗):BSA generates (1)O2 with quantum yield ΦΔ = 0.35 ± 0.05. In turns, the intraprotein generated (1)O2 is able to diffuse through the bulk solution, where is dynamically quenched by BSA itself with an overall quenching rate constant of 7.3 × 10(8) M(-1) s(-1). However, at n>1, nonspecific binding of up to ≈ 6RB molecules per BSA is produced, allowing efficient static quenching of excited states of RB preventing photosensitization of (1)O2. These results provide useful information for development of dye-protein adducts suitable for using as potential intracellular photosensitizers. Copyright © 2014 Elsevier B.V. All rights reserved.

Real-Time Monitoring of Singlet Oxygen and Oxygen Partial Pressure During the Deep Photodynamic Therapy In Vitro.

PubMed

Li, Weitao; Huang, Dong; Zhang, Yan; Liu, Yangyang; Gu, Yueqing; Qian, Zhiyu

2016-09-01

Photodynamic therapy (PDT) is an effective noninvasive method for the tumor treatment. The major challenge in current PDT research is how to quantitatively evaluate therapy effects. To our best knowledge, this is the first time to combine multi-parameter detection methods in PDT. More specifically, we have developed a set of system, including the high-sensitivity measurement of singlet oxygen, oxygen partial pressure and fluorescence image. In this paper, the detection ability of the system was validated by the different concentrations of carbon quantum dots. Moreover, the correlation between singlet oxygen and oxygen partial pressure with laser irradiation was observed. Then, the system could detect the signal up to 0.5 cm tissue depth with 660 nm irradiation and 1 cm tissue depth with 980 nm irradiation by using up-conversion nanoparticles during PDT in vitro. Furthermore, we obtained the relationship among concentration of singlet oxygen, oxygen partial pressure and tumor cell viability under certain conditions. The results indicate that the multi-parameter detection system is a promising asset to evaluate the deep tumor therapy during PDT. Moreover, the system might be potentially used for the further study in biology and molecular imaging.

Decontamination of chemical-warfare agent simulants by polymer surfaces doped with the singlet oxygen generator zinc octaphenoxyphthalocyanine.

PubMed

Gephart, Raymond T; Coneski, Peter N; Wynne, James H

2013-10-23

Using reactive singlet oxygen (1O2), the oxidation of chemical-warfare agent (CWA) simulants has been demonstrated. The zinc octaphenoxyphthalocyanine (ZnOPPc) complex was demonstrated to be an efficient photosensitizer for converting molecular oxygen (O2) to 1O2 using broad-spectrum light (450-800 nm) from a 250 W halogen lamp. This photosensitization produces 1O2 in solution as well as within polymer matrices. The oxidation of 1-naphthol to naphthoquinone was used to monitor the rate of 1O2 generation in the commercially available polymer film Hydrothane that incorporates ZnOPPc. Using electrospinning, nanofibers of ZnOPPc in Hydrothane and polycarbonate were formed and analyzed for their ability to oxidize demeton-S, a CWA simulant, on the surface of the polymers and were found to have similar reactivity as their corresponding films. The Hydrothane films were then used to oxidize CWA simulants malathion, 2-chloroethyl phenyl sulfide (CEPS), and 2-chloroethyl ethyl sulfide (CEES). Through this oxidation process, the CWA simulants are converted into less toxic compounds, thus decontaminating the surface using only O2 from the air and light.

Singlet Oxygen and Free Radical Reactions of Retinoids and Carotenoids—A Review

PubMed Central

Truscott, T. George

2018-01-01

We report on studies of reactions of singlet oxygen with carotenoids and retinoids and a range of free radical studies on carotenoids and retinoids with emphasis on recent work, dietary carotenoids and the role of oxygen in biological processes. Many previous reviews are cited and updated together with new data not previously reviewed. The review does not deal with computational studies but the emphasis is on laboratory-based results. We contrast the ease of study of both singlet oxygen and polyene radical cations compared to neutral radicals. Of particular interest is the switch from anti- to pro-oxidant behavior of a carotenoid with change of oxygen concentration: results for lycopene in a cellular model system show total protection of the human cells studied at zero oxygen concentration, but zero protection at 100% oxygen concentration. PMID:29301252

Synthesis, supramolecular behavior, and in vitro photodynamic activities of novel zinc(II) phthalocyanines "side-strapped" with crown ether bridges.

PubMed

Chen, Xing-Wei; Ke, Mei-Rong; Li, Xing-Shu; Lan, Wen-Liang; Zhang, Miao-Fen; Huang, Jian-Dong

2013-12-01

Two new tetra- or di-α-substituted zinc(II) phthalocyanines 5 and 6 have been prepared through a "side-strapped" method. In the molecules, the adjacent benzene rings of the phthalocyanine core are linked at α-position through a triethylene glycol bridge to form a hybrid aza-/oxa-crown ether. The tetra-α-substituted phthalocyanine 5 shows an eclipsed self-assembly property in CH2Cl2 and the effect on the di-α-substituted analogue 6 is significantly weakened. Furthermore, the crown ethers of these compounds can selectively complex with Fe(3+) or Cu(2+) ion in DMF, leading to formation of J-aggregated nano-assemblies, which can be disaggregated in the presence of some organic or inorganic ligands, such as triethylamine, tetramethylethylenediamine, CH3COO(-), or OH(-). In addition, both compounds are efficient singlet oxygen generators with the singlet oxygen quantum yields (Φ(Δ)) of 0.54-0.74 in DMF relative to unsubstituted zinc(II) phthalocyanine (Φ(Δ)=0.56). They exhibit photodynamic activities toward HepG2 human hepatocarcinoma cells, but the compound 6, which has more than 40-fold lower IC50 value (0.08 μM) compared to the analogue 5 (IC50=3.31 μM), shows remarkablely higher in vitro photocytotoxicity due to its significantly higher cellular uptake and singlet oxygen generation efficiency. The results suggest that these compounds can serve as promising multifunctional materials both in (opto)electronic field and photodynamic therapy. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatially resolved measurement of singlet delta oxygen by radar resonance-enhanced multiphoton ionization.

PubMed

Wu, Yue; Zhang, Zhili; Ombrello, Timothy M

2013-07-01

Coherent microwave Rayleigh scattering (Radar) from resonance-enhanced multiphoton ionization (REMPI) was demonstrated to directly and nonintrusively measure singlet delta oxygen, O(2)(a(1)Δ(g)), with high spatial resolution. Two different approaches, photodissociation of ozone and microwave discharge plasma in an argon and oxygen flow, were utilized for O(2)(a(1)Δ(g)) generation. The d(1)Π(g)←a(1)Δ(g) (3-0) and d(1)Π(g)←a(1)Δ(g) (1-0) bands of O(2)(a(1)Δ(g)) were detected by Radar REMPI for two different flow conditions. Quantitative absorption measurements using sensitive off-axis integrated cavity output spectroscopy (ICOS) was used simultaneously to evaluate the accuracy and sensitivity of the Radar REMPI technique. The detection limit of Radar REMPI was found to be comparable to the ICOS technique with a detection threshold of approximately 10(14) molecules/cm(3) but with a spatial resolution that was 8 orders of magnitude smaller than the ICOS technique.

Drug Carrier for Photodynamic Cancer Therapy

PubMed Central

Debele, Tilahun Ayane; Peng, Sydney; Tsai, Hsieh-Chih

2015-01-01

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S0) to an excited singlet state (S1–Sn), followed by intersystem crossing to an excited triplet state (T1). The energy transferred from T1 to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (1O2, H2O2, O2*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer. PMID:26389879

On the atmospheric oxidation of liquid toluene.

PubMed

Pritchard, Huw O

2006-10-21

This communication presents preliminary computational results on the interaction between triplet (3Sigma) and singlet (1Sigma, 1Delta) oxygen molecules with toluene. All three oxygen species form very weak complexes with toluene and all also appear capable of abstracting a benzylic hydrogen atom to form the HO2 radical. Reaction with singlet molecular oxygen does not convincingly explain the formation of benzylhydroperoxide from toluene residues stored over a long time in brown glass bottles, and it is speculated that this may be a surface-catalysed photochemical reaction. The possible involvement of singlet oxygen molecules in the spontaneous ignition of tyre rubber and of soft coal is discussed briefly and the need for new experimental studies is stressed.

Calculation of the mixing chamber of an ejector chemical oxygen - iodine laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagidullin, M V; Nikolaev, V D

2001-06-30

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen-iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of the exhaust gas to the atmosphere by using a diffuser and single-stage vacuum systems based on water circulating pumps. (lasers, active media)

Synthesis and evaluation of sensitizer drug photorelease chemistry: Micro-optic method applied to singlet oxygen generation and drug delivery

NASA Astrophysics Data System (ADS)

Ghosh, Goutam

This thesis summarizes a new micro-optic method for singlet oxygen generation and sensitizer drug delivery, which include i) synthesis and evaluation of a first generation device for drug delivery from native and fluorinated silica probe tips, ii) synthesis of PEG conjugated sensitizers to study phototoxicity in ovarian cancer cells, and iii) synthesis and evaluation of tris-PEGylated chlorin conjugated fluorinated silica for its future integration into the device to use as a 2nd generation device. A first generation micro-optic device was developed that works by sparging O2 gas and light generating cytotoxic singlet oxygen that cleaves the covalently attached drug (sensitizer) from the probe tip at the distal end of the fiber. The aim is to develop a 1st and 2nd generation device for site specific delivery of photosensitizer and singlet oxygen to overcome the challenges involved in systemic administration of the sensitizer. Synthesis and evaluation of drug (pheophorbide-a) delivery applying micro-optic method from native and fluorinated silica probe tip was achieved. The amount of sensitizer photocleavage depends on the loading level of sensitizer onto the probe tips. We also found that photorelease efficiency depends on the nature of the solvents where sensitizer is photocleaved. For example, no photorelease was observed in an aqueous solvent where sensitizer remained adsorbed to the native silica probe-tip. But, 90% photocleavage was obtained in octanol. A significant amount of photosensitizer (formate ester of pyropheophorbide- a) diffused into the liposome when photocleavage study was carried out in liposome. Substantial increase of photorelease was observed in organic solvent when pyropheophorbide-a (PPa) sensitizer was attached to the partially fluorinated porous Vycor glass. We also explored sensitizer photorelease from the fluorinated silica surface at various temperatures and we found that autocatalytic photorelease happened at room temperature and above. No photorelease was observed at low temperature. Chlorin e6 and its one, two and three short chain methoxy triethylene glycol (PEG) conjugated derivatives were synthesized. A comparative study of photocytotoxicity and cellular uptake between each showed that 17 3,152,131- chlorin e6 methoxy triethylene glycol triester has the highest photocytotoxic activity and uptake by ovarian OVCAR-5 cancer cells. Therefore, we decided to load three short chain PEG conjugated chlorin e6 onto the silica surface through spacer alkene for delivery via a fiber-optic probe tip. In order to load chlorin e6-triPEG ester conjugate, in chapter 4, we explored different synthetic strategies. We have been successful in synthesizing spacer alkene succinate linker conjugated chlorin e6 -tri PEG ester, which was attached to the fiber-optic probe tip. Reactions were carried out in mild conditions to avoid detachment of the PEG ester from the carboxylic acid sites of chlorin. Photocleavage of the triPEG modified fluorinated probe tip system was studied in n-butanol.

Singlet Oxygen Reactions with Flavonoids. A Theoretical – Experimental Study

PubMed Central

Morales, Javier; Günther, Germán; Zanocco, Antonio L.; Lemp, Else

2012-01-01

Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid. PMID:22802966

Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

PubMed

Morales, Javier; Günther, Germán; Zanocco, Antonio L; Lemp, Else

2012-01-01

Detection of singlet oxygen emission, λ(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(r), for the reaction between singlet oxygen and several flavonoids. Values of k(T) determined in deuterated water, ranging from 2.4×10(7) M(-1) s(-1) to 13.4×10(7) M(-1) s(-1), for rutin and morin, respectively, and the values measured for k(r), ranging from 2.8×10(5) M(-1) s(-1) to 65.7×10(5) M(-1) s(-1) for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

Predicting apparent singlet oxygen quantum yields of dissolved black carbon and humic substances using spectroscopic indices.

PubMed

Du, Ziyan; He, Yingsheng; Fan, Jianing; Fu, Heyun; Zheng, Shourong; Xu, Zhaoyi; Qu, Xiaolei; Kong, Ao; Zhu, Dongqiang

2018-03-01

Dissolved black carbon (DBC) is ubiquitous in aquatic systems, being an important subgroup of the dissolved organic matter (DOM) pool. Nevertheless, its aquatic photoactivity remains largely unknown. In this study, a range of spectroscopic indices of DBC and humic substance (HS) samples were determined using UV-Vis spectroscopy, fluorescence spectroscopy, and proton nuclear magnetic resonance. DBC can be readily differentiated from HS using spectroscopic indices. It has lower average molecular weight, but higher aromaticity and lignin content. The apparent singlet oxygen quantum yield (Φ singlet oxygen ) of DBC under simulated sunlight varies from 3.46% to 6.13%, significantly higher than HS, 1.26%-3.57%, suggesting that DBC is the more photoactive component in the DOM pool. Despite drastically different formation processes and structural properties, the Φ singlet oxygen of DBC and HS can be well predicted by the same simple linear regression models using optical indices including spectral slope coefficient (S 275-295 ) and absorbance ratio (E 2 /E 3 ) which are proxies for the abundance of singlet oxygen sensitizers and for the significance of intramolecular charge transfer interactions. The regression models can be potentially used to assess the photoactivity of DOM at large scales with in situ water spectrophotometry or satellite remote sensing. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of the oxygenation level on formation of different reactive oxygen species during photodynamic therapy.

PubMed

Price, Michael; Heilbrun, Lance; Kessel, David

2013-01-01

We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage, but via different photochemical pathways. Upon irradiation, the chlorin termed NPe6 forms singlet oxygen in high yield while the bacteriopheophorbide WST11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilling by NPe6 was unaffected. Studies in a cell-free system revealed that the rates of photobleaching of these agents, as a function of the oxygenation level, were correlated with results described above. Moreover, the rate of formation of oxygen radicals by either agent was more sensitive to the level of oxygenation than was singlet oxygen formation by NPe6. These data indicate that the photochemical process that leads to oxygen radical formation is more dependent on the oxygenation level than is the pathway leading to formation of singlet oxygen. © 2013 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2013 The American Society of Photobiology.

Photoinduced formation of reactive oxygen species and electrons from metal oxide-silica nanocomposite: An EPR spin-trapping study

NASA Astrophysics Data System (ADS)

Zhao, Hongxia; Chen, Xiuying; Li, Xintong; Shen, Chen; Qu, Baocheng; Gao, Jingsuo; Chen, Jingwen; Quan, Xie

2017-09-01

Metal oxide nanocomposites with photocatalytic activity have the potential for many applications in environmental remediation and biomedicine. In this study, we investigated the formation and stabilization of electrons/holes from three metal oxide-silica nanocomposites (CuO-SiO2, Fe2O3-SiO2 and ZnO-SiO2) under irradiation by electron paramagnetic resonance (EPR) technology. The characteristic EPR signals with g = 2.00070-2.00105, ΔHp-p = 2.17-2.37 G were determined, which corresponded to lattice-trapped electrons. Moreover, the generation of active species from CuO-SiO2, Fe2O3-SiO2 and ZnO-SiO2 in aqueous solution under irradiation was also systematically studied. The results showed that all the three nanocomposites could generate hydroxyl radical, singlet oxygen and electron. CuO-SiO2 was more effective than Fe2O3-SiO2 and ZnO-SiO2 in producing hydroxyl radical and electrons, while ZnO-SiO2 was the most efficient in generating singlet oxygen. In addition, CuO-SiO2 exhibited most obviously photocatalytic activity toward degradation of bisphenol A, followed by Fe2O3-SiO2 and ZnO-SiO2. These findings will provide vital insights into photocatalytic mechanisms and potentially photoinduced toxicity of metal oxide-silica nanocomposites.

No Photon Wasted: An Efficient and Selective Singlet Oxygen Photosensitizing Protein.

PubMed

Westberg, Michael; Bregnhøj, Mikkel; Etzerodt, Michael; Ogilby, Peter R

2017-10-12

Optogenetics has been, and will continue to be, a boon to mechanistic studies of cellular processes. Genetically encodable proteins that sensitize the production of reactive oxygen species (ROS) are expected to play an increasingly important role, particularly in elucidating mechanisms of temporally and spatially dependent cell signaling. However, a substantial challenge in developing such photosensitizing proteins has been to funnel the optical excitation energy into the initial selective production of only one ROS. Singlet molecular oxygen, O 2 (a 1 Δ g ), is a ROS known to have a wide range of effects on cell function. Nevertheless, mechanistic details of singlet oxygen's behavior in a cell are lacking. On the basis of the rational optimization of a LOV-derived flavoprotein, we now report the development and photophysical characterization of a protein-encased photosensitizer that efficiently and selectively produces singlet oxygen at the expense of other ROS, especially ROS that derive from photoinduced electron transfer reactions. These results set the stage for a plethora of new experiments to elucidate ROS-mediated events in cells.

Copper phthalocyanine-based CMPs with various internal structures and functionalities.

PubMed

Ding, Xuesong; Han, Bao-Hang

2015-08-18

Several kinds of copper phthalocyanine-based conjugated microporous polymers have been synthesized, which present enhanced long-wavelength photon absorption capability and high efficiency for singlet oxygen generation under low energy light irradiation. This strategy opens a facile avenue towards expanding the scope of phthalocyanine-based porous materials with various internal structures and functionalities.

Photodynamic Therapy for Cancer Cells Using a Flash Wave Light Xenon Lamp

NASA Astrophysics Data System (ADS)

Kimura, Makoto; Kashikura, Kasumi; Yokoi, Satomi; Koiwa, Yumiko; Tokuoka, Yoshikazu; Kawashima, Norimichi

We determined photodynamic therapy (PDT) efficacy using a flash wave (FW) and a continuous wave (CW) light, of which the fluence rate was 70 W/cm2, for murine thymic lymphoma cells (EL-4) cultivated in vitro. The irradiation frequency and the pulse width of the FW light were in the range of 1-32 Hz and less than one millisecond, respectively. 5-Aminolevulinic acid-induced protoporphyrin IX (ALA-PpIX) was used as a photosensitizer. When EL-4 with ALA administration was irradiated by the light for 4 h (irradiation fluence: 1.0J/cm2), the survival rate of EL-4 by the FW light was lower than that by the CW light, except for the FW light with irradiation frequency of 32 Hz, and decreased gradually with decreasing irradiation frequency. Moreover, the FW light, especially at lower irradiation frequency, was superior to the CW light for the generation of singlet oxygen in an aqueous PpIX solution. Therefore, thehigher PDT efficacy for EL-4 of the FW light would be caused by the greater generation of singlet oxygen in the cells.

Optimization of singlet oxygen production from photosensitizer-incorporated, medically relevant hydrogels.

PubMed

De Baróid, Áine T; McCoy, Colin P; Craig, Rebecca A; Carson, Louise; Andrews, Gavin P; Jones, David S; Gorman, Sean P

2017-02-01

Photodynamic therapy and photodynamic antimicrobial chemotherapy are widely used, but despite this, the relationships between fluence, wavelength of irradiation and singlet oxygen ( 1 O 2 ) production are poorly understood. To establish the relationships between these factors in medically relevant materials, the effect of fluence on 1 O 2 production from a tetrakis(4-N-methylpyridyl)porphyrin (TMPyP)-incorporated 2-hydroxyethyl methacrylate: methyl methacrylate: methacrylic acid (HEMA: MMA:MAA) copolymer, a total energy of 50.48 J/cm 2 , was applied at varying illumination power, and times. 1 O 2 production was characterized using anthracene-9,10-dipropionic acid, disodium salt (ADPA) using a recently described method. Using two light sources, a white LED array and a white halogen source, the LED array was found to produce less 1 O 2 than the halogen source when the same power (over 500 - 600 nm) and time conditions were applied. Importantly, it showed that the longest wavelength Q band (590 nm) is primarily responsible for 1 O 2 generation, and that a linear relationship exists between increasing power and time and the production of singlet oxygen. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 320-326, 2017. © 2015 The Authors Journal Of Biomedical Materials Research Part B: Applied Biomaterials Published By Wiley Periodicals, Inc.

Generation of ROS mediated by mechanical waves (ultrasound) and its possible applications.

PubMed

Duco, Walter; Grosso, Viviana; Zaccari, Daniel; Soltermann, Arnaldo T

2016-10-15

The thermal decomposition of 9,10 diphenylanthracene peroxide (DPAO 2 ) generates DPA and a mix of triplet and singlet molecular oxygen. For DPAO 2 the efficiency to produce singlet molecular oxygen is 0.35. On the other hand, it has shown that many thermal reactions can be carried out through the interaction of molecules with ultrasound. Ultrasound irradiation can create hydrodynamic stress (sonomechanical process), inertial cavitation (pyrolitic process) and long range effects mediated by radicals or ROS. Sonochemical reactions can be originated by pyrolytic like process, shock mechanical waves, thermal reactions and radical and ROS mediated reactions. Sonolysis of pure water can yield hydrogen or hydroxyl radicals and hydrogen peroxide (ROS). When DPAO 2 in 1,4 dioxane solution is treated with 20 or 24kHz and different power intensity the production of molecular singlet oxygen is observed. Specific scavengers like tetracyclone (TC) are used to demonstrate it. The efficiency now is 0.85 showing that the sonochemical process is much more efficient that the thermal one. Another endoperoxide, artemisinin was also studied. Unlike the concept of photosensitizer of photodynamic therapy, in spite of large amount of reported results in literature, the term sonosensitizer and the sonosensitization process are not well defined. We define sonosensitized reaction as one in which a chemical species decompose as consequence of cavitation phenomena producing ROS or other radicals and some other target species does undergo a chemical reaction. The concept could be reach rapidly other peroxides which are now under experimental studies. For artemisinin, an important antimalarian and anticancer drug, was established that ultrasound irradiation increases the effectiveness of the treatment but without any explanation. We show that artemisinin is an endoperoxide and behaves as a sonosensitizer in the sense of our definition. Copyright © 2016 Elsevier Inc. All rights reserved.

Singlet oxygen-based electrosensing by molecular photosensitizers

NASA Astrophysics Data System (ADS)

Trashin, Stanislav; Rahemi, Vanoushe; Ramji, Karpagavalli; Neven, Liselotte; Gorun, Sergiu M.; de Wael, Karolien

2017-07-01

Enzyme-based electrochemical biosensors are an inspiration for the development of (bio)analytical techniques. However, the instability and reproducibility of the reactivity of enzymes, combined with the need for chemical reagents for sensing remain challenges for the construction of useful devices. Here we present a sensing strategy inspired by the advantages of enzymes and photoelectrochemical sensing, namely the integration of aerobic photocatalysis and electrochemical analysis. The photosensitizer, a bioinspired perfluorinated Zn phthalocyanine, generates singlet-oxygen from air under visible light illumination and oxidizes analytes, yielding electrochemically-detectable products while resisting the oxidizing species it produces. Compared with enzymatic detection methods, the proposed strategy uses air instead of internally added reactive reagents, features intrinsic baseline correction via on/off light switching and shows C-F bonds-type enhanced stability. It also affords selectivity imparted by the catalytic process and nano-level detection, such as 20 nM amoxicillin in μl sample volumes.

Singlet oxygen-based electrosensing by molecular photosensitizers

PubMed Central

Trashin, Stanislav; Rahemi, Vanoushe; Ramji, Karpagavalli; Neven, Liselotte; Gorun, Sergiu M.; De Wael, Karolien

2017-01-01

Enzyme-based electrochemical biosensors are an inspiration for the development of (bio)analytical techniques. However, the instability and reproducibility of the reactivity of enzymes, combined with the need for chemical reagents for sensing remain challenges for the construction of useful devices. Here we present a sensing strategy inspired by the advantages of enzymes and photoelectrochemical sensing, namely the integration of aerobic photocatalysis and electrochemical analysis. The photosensitizer, a bioinspired perfluorinated Zn phthalocyanine, generates singlet-oxygen from air under visible light illumination and oxidizes analytes, yielding electrochemically-detectable products while resisting the oxidizing species it produces. Compared with enzymatic detection methods, the proposed strategy uses air instead of internally added reactive reagents, features intrinsic baseline correction via on/off light switching and shows C-F bonds-type enhanced stability. It also affords selectivity imparted by the catalytic process and nano-level detection, such as 20 nM amoxicillin in μl sample volumes.

High-sensitivity imaging method of singlet oxygen and superoxide anion in photodynamic and sonodynamic actions

NASA Astrophysics Data System (ADS)

Xing, Da; He, Yonghong; Hao, Min; Chen, Qun

2004-07-01

A novel method of photodynamic diagnosis (PDD) of cancer mediated by chemiluminescence (CL) probe is presented. The mechanism for photodynamic therapy (PDT) involves reactive oxygen species (ROS), such as singlet oxygen (1O2) and superoxide (O2-), generated by during the photochemical process. Both 1O2 and O2- can react with Cypridina luciferin analogue (FCLA), a highly selective CL probe for detecting the ROS. Chemiluminescence from the reaction of FCLA with the ROS, at about 530 nm, was detected by a highly sensitive ICCD system. The CL was markedly inhibited by the addition of 10 mmol/L sodium azide (NaN3) in a sample solution. Similar phenomena, with lesser extents of changes, were observed at the additions of 10 μmol/L superoxide dismutase (SOD), 10 mmol/L mannitol, and 100 μg/mL catalase, respectively. This indicates that the detected CL signals were mainly from ROS generated during the photosensitization reactions. Also, the chemiluminescence method was used to detect the ROS during sonodynamic action, both in vitro and in vivo. ROS formation during sonosensitizations of HpD and ATX-70 were detected using our newly-developed imaging technique, in real time, on tumor bearing animals. This method can provide a new means in clinics for tumor diagnosis.

Lactofen induces isoflavone accumulation and glyceollin elicitation competency in soybean.

PubMed

Landini, Serena; Graham, Madge Y; Graham, Terrence L

2003-03-01

Lactofen, the active ingredient of the soybean disease resistance-inducing herbicide, Cobra, induces large accumulations of isoflavone conjugates and aglycones in soybean tissues. The predominant isoflavones induced in cotyledon tissues are daidzein (and its conjugates) and formononetin and glycitein aglycones. The latter two isoflavones are usually present only at very low levels in soybean seedling tissues. In leaves, the predominant lactofen-induced isoflavones are daidzein and formononetin aglycones and the malonyl-glucosyl conjugate of genistein. Isoflavone induction also occurs in cells distal to the point of treatment, but is only weakly systemic. Lactofen also induces elicitation competency, the capacity of soybean cells to accumulate the pterocarpan phytoalexin glyceollin in response to glucan elicitors from the cell wall of the pathogen Phytophthora sojae. Comparison of the activity of a series of diphenyl ether herbicides demonstrated that while all diphenyl ethers tested induced some degree of elicitation competency, only certain ones induced isoflavone accumulation in the absence of glucan elicitor. As a group the diphenyl ethers are thought to inhibit protoporhyrinogen oxidase, eventually leading to singlet oxygen generation. Another singlet oxygen generator, rose bengal, also induced elicitation competency, but little isoflavone accumulation. It is hypothesized that diphenyl ether-induced activated oxygen species mimic some aspects of hypersensitive cell death, which leads to elicitation competency in infected tissues.

Voltage-sensitive styryl dyes as singlet oxygen targets on the surface of bilayer lipid membrane.

PubMed

Sokolov, V S; Gavrilchik, A N; Kulagina, A O; Meshkov, I N; Pohl, P; Gorbunova, Yu G

2016-08-01

Photosensitizers are widely used as photodynamic therapeutic agents killing cancer cells by photooxidation of their components. Development of new effective photosensitive molecules requires profound knowledge of possible targets for reactive oxygen species, especially for its singlet form. Here we studied photooxidation of voltage-sensitive styryl dyes (di-4-ANEPPS, di-8-ANEPPS, RH-421 and RH-237) by singlet oxygen on the surface of bilayer lipid membranes commonly used as cell membrane models. Oxidation was induced by irradiation of a photosensitizer (aluminum phthalocyanine tetrasulfonate) and monitored by the change of dipole potential on the surface of the membrane. We studied the drop of the dipole potential both in the case when the dye molecules were adsorbed on the same side of the lipid bilayer as the photosensitizer (cis-configuration) and in the case when they were adsorbed on the opposite side (trans-configuration). Based on a simple model, we determined the rate of oxidation of the dyes from the kinetics of change of the potential during and after irradiation. This rate is proportional to steady-state concentration of singlet oxygen in the membrane under irradiation. Comparison of the oxidation rates of various dyes reveals that compounds of ANEPPS series are more sensitive to singlet oxygen than RH type dyes, indicating that naphthalene group is primarily responsible for their oxidation. Copyright © 2016 Elsevier B.V. All rights reserved.

Hypocrellin B and nano silver loaded polymeric nanoparticles: Enhanced generation of singlet oxygen for improved photodynamic therapy.

PubMed

Natesan, Subramanian; Krishnaswami, Venkateshwaran; Ponnusamy, Chandrasekar; Madiyalakan, Madi; Woo, Thomas; Palanisamy, Rajaguru

2017-08-01

A nanoparticulate photodynamic approach was employed with an objective to achieve enhanced production of singlet oxygen ( 1 O 2 ), for the management of posterior segment eye diseases like age related macular degeneration. The hypocrellin B (HB) loaded poly lactide-co-glycolide nanoparticle formulations were incorporated with nano silver (HBS-NPs). The optimized HBS-NPs contained 2.60±0.06mg/mL of HB and showed (i) 135.6 to 828.2nm size range, and (ii) negative zeta potential with a narrow polydispersity index. The DSC thermograms suggested the amorphous nature of HB inside the HBS-NPs. With the average encapsulation efficiency of 92.9±1.79%, the drug release from the HBS-NPs followed a biphasic pattern with an initial burst of 3.50% during first 8h followed by a sustained release of 47.82% within 3days. The interaction between nano silver and HB as assessed by the increase in spectral intensity of Raman spectrum demonstrates that HB may be attached over the nano silver. Generation of reactive oxygen species (ROS) by HBS-NPs was significantly higher than that of HB/HB-NPs. The singlet oxygen generating efficiency assessed using EPR spectrometer follows the order of nano silver>HB-NPs>pure HB drug solution>HBS-NPs. The HBS-NPs had a concentration and time dependent phototoxicity on A549 (human adeno lung carcinoma) cells in the presence of light providing a superior phototoxic effect (82.2% at 50μM) at 2h irradiation. The CAM treated with HBS-NPs showed a significant anti-angiogenic effect compared to a blank formulation. In vivo biodistribution studies revealed that intravenous administration of HBS-NPs lead into significant exposure to the posterior segment of the eye. This proof of principle study demonstrates that HB based nanoparticles may be a valuable new tool for application in ocular photodynamic therapy for the treatment of AMD in future. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultraviolet-A1 irradiation therapy for systemic lupus erythematosus.

PubMed

McGrath, H

2017-10-01

Systemic lupus erythematosus (lupus, SLE) is a chronic autoimmune disease characterized by the production of autoantibodies, which bind to antigens and are deposited within tissues to fix complement, resulting in widespread systemic inflammation. The studies presented herein are consistent with hyperpolarized, adenosine triphosphate (ATP)-deficient mitochondria being central to the disease process. These hyperpolarized mitochondria resist the depolarization required for activation-induced apoptosis. The mitochondrial ATP deficits add to this resistance to apoptosis and also reduce the macrophage energy that is needed to clear apoptotic bodies. In both cases, necrosis, the alternative pathway of cell death, results. Intracellular constituents spill into the blood and tissues, eliciting inflammatory responses directed at their removal. What results is "autoimmunity." Ultraviolet (UV)-A1 photons have the capacity to remediate this aberrancy. Exogenous exposure to low-dose, full-body, UV-A1 radiation generates singlet oxygen. Singlet oxygen has two major palliative actions in patients with lupus and the UV-A1 photons themselves have several more. Singlet oxygen depolarizes the hyperpolarized mitochondrion, triggering non-ATP-dependent apoptosis that deters necrosis. Next, singlet oxygen activates the gene encoding heme oxygenase (HO-1), a major governor of systemic homeostasis. HO-1 catalyzes the degradation of the oxidant heme into biliverdin (converted to bilirubin), Fe, and carbon monoxide (CO), the first three of these exerting powerful antioxidant effects, and in conjunction with a fourth, CO, protecting against injury to the coronary arteries, the central nervous system, and the lungs. The UV-A1 photons themselves directly attenuate disease in lupus by reducing B cell activity, preventing the suppression of cell-mediated immunity, slowing an epigenetic progression toward SLE, and ameliorating discoid and subacute cutaneous lupus. Finally, a combination of these mechanisms reduces levels of anticardiolipin antibodies and protects during lupus pregnancy. Capping all of this is that UV-A1 irradiation is an essentially innocuous, highly manageable, and comfortable therapeutic agency.

Ultraviolet-A1 irradiation therapy for systemic lupus erythematosus

PubMed Central

2017-01-01

Systemic lupus erythematosus (lupus, SLE) is a chronic autoimmune disease characterized by the production of autoantibodies, which bind to antigens and are deposited within tissues to fix complement, resulting in widespread systemic inflammation. The studies presented herein are consistent with hyperpolarized, adenosine triphosphate (ATP)-deficient mitochondria being central to the disease process. These hyperpolarized mitochondria resist the depolarization required for activation-induced apoptosis. The mitochondrial ATP deficits add to this resistance to apoptosis and also reduce the macrophage energy that is needed to clear apoptotic bodies. In both cases, necrosis, the alternative pathway of cell death, results. Intracellular constituents spill into the blood and tissues, eliciting inflammatory responses directed at their removal. What results is “autoimmunity.” Ultraviolet (UV)-A1 photons have the capacity to remediate this aberrancy. Exogenous exposure to low-dose, full-body, UV-A1 radiation generates singlet oxygen. Singlet oxygen has two major palliative actions in patients with lupus and the UV-A1 photons themselves have several more. Singlet oxygen depolarizes the hyperpolarized mitochondrion, triggering non-ATP-dependent apoptosis that deters necrosis. Next, singlet oxygen activates the gene encoding heme oxygenase (HO-1), a major governor of systemic homeostasis. HO-1 catalyzes the degradation of the oxidant heme into biliverdin (converted to bilirubin), Fe, and carbon monoxide (CO), the first three of these exerting powerful antioxidant effects, and in conjunction with a fourth, CO, protecting against injury to the coronary arteries, the central nervous system, and the lungs. The UV-A1 photons themselves directly attenuate disease in lupus by reducing B cell activity, preventing the suppression of cell-mediated immunity, slowing an epigenetic progression toward SLE, and ameliorating discoid and subacute cutaneous lupus. Finally, a combination of these mechanisms reduces levels of anticardiolipin antibodies and protects during lupus pregnancy. Capping all of this is that UV-A1 irradiation is an essentially innocuous, highly manageable, and comfortable therapeutic agency. PMID:28480786

Mitochondria-targeting for improved photodynamic therapy

NASA Astrophysics Data System (ADS)

Ngen, Ethel J.

Photodynamic therapy (PDT) is an emerging cancer therapeutic modality, with great potential to selectively treat surface cancers, thus minimizing systemic side effects. In this dissertation, two approaches to deliver photosensitizers to mitochondria were investigated: 1) Reducing photosensitizer sizes to improve endocytosis and lysosomal localization. Upon irradiation the photosensitizers would then produce singlet oxygen which could rupture the lysosomal membrane releasing the lysosomally trapped photosensitizers to the cytosol, from where they could relocalize to mitochondria by passive diffusion (photochemical internalization). 2) Using delocalized lipophilic cationic dyes (DLCs) to exploit membrane potential differences between the cytoplasm and mitochondria in delivering photosensitizers to mitochondria. To investigate the effects of steric hindrance on mitochondrial localization and photodynamic response, a series of eight thiaporphyrins were studied. Two new thiaporphyrin analogues 6 and 8 with reduced steric hindrance at the 10- and 15- meso positions were studied in comparison to 5,20-diphenyl-10,15-bis[4 (carboxymethyleneoxy)-phenyl]-21,23-dithiaporphyrin 1, previously validated as a potential second generation photosensitizer. Although 6 showed an extraordinarily high uptake (7.6 times higher than 1), it was less potent than 1 (IC 50 = 0.18 muM versus 0.13 muM) even though they both showed similar sub-cellular localization patterns. This low potency was attributed to its high aggregation tendency in aqueous media (4 times higher than 1), which might have affected its ability to generate singlet oxygen in vitro . 8 on the other hand showed an even lower potency than 6 (2.28 vs 0.18 muM). However this was attributed to its low cellular uptake (20 times less than 6) and inefficient generation of singlet oxygen. Overall, although the structural modifications did improve the cellular uptake of 6, 6 was still less potent than the lead photosensitizers 1. Thus, other strategies to target mitochondria for improved photodynamic activity were investigated. In a continuing project, we evaluated the ability of delocalized lipophilic cationic dyes to deliver photosensitizers to mitochondria by exploiting the membrane potential difference between the cytoplasm and mitochondria. Two conjugates: a porphyrin--rhodamine B conjugate (TPP--Rh) and a porphyrin-acridine orange conjugate (TPP--AO), each possessing a single delocalized lipophilic cation, were designed and synthesized. The conjugates were synthesized by conjugating a monohydroxy porphyrin (TPP-OH) to rhodamine B (Rh B) and acridine orange base (AO), respectively, via saturated hydrocarbon linkers. To evaluate the efficiency of the conjugates as photosensitizers, their photophysical properties and in vitro photodynamic activities were studied in comparison to those of TPP-OH, the parent porphyrin photosensitizer. Although fluorescence energy transfer (FRET) was observed in the conjugates, they were capable of generating singlet oxygen at rates comparable to TPP-OH. In a final project, we evaluated the photophysical potential of TPP-Rh to act as a two-photon photosensitizer for PDT. Two-photon PDT is a rational approach used to improve light penetration through the skin. Rhodamine B is an effective two-photon chromophore and could significantly improve the two-photon absorption of the porphyrin photosensitizer in the TPP-Rh dyad system following energy transfer. Thus the porphyrin--rhodamine B dyad (TPP--Rh), previously demonstrated to preferentially accumulate in the mitochondria, was photophysically evaluated as a potential two-photon photosensitizer. To evaluate the efficiency of TPP-Rh as a two-photon photosensitizer, its two-photon photophysical properties were compared with those of its individual components (Rh B and TPP-OH). This included: the two-photon cross sections (sigma 2), RET kinetics and dynamics and rates of singlet oxygen generation. A FRET efficiency of ~99 % was observed from the Rh moiety (donor) to the TPP moiety (acceptor) of the system. This significantly enhanced the sigma 2 of TPP-Rh by ˜ 100 % (20 GM) compared to the parent TPP-OH. Furthermore, TPP-Rh produced singlet oxygen at a significantly faster rate than TPP-OH upon two-photon excitation. Thus, this indicates that conjugating photosensitizers to Rh B via short saturated hydrocarbon linkers could provide deeper tissue penetration, in addition to preferential mitochondrial accumulation for improved photodynamic response. (Abstract shortened by UMI.)

PHOTOGENERATION OF SINGLET OXYGEN AND FREE RADICALS IN DISSOLVED ORGANIC MATTER ISOLATED FROM THE MISSISSIPPI AND ATCHAFALAYA RIVER PLUMES

EPA Science Inventory

The photoreactivity to UV light of ultrafiltered dissolved organic matter (DOM) collected during cruises along salinity transects in the Mississippi and Atchafalaya River plumes was examined by measuring photogenerated free radicals and singlet molecular oxygen (1O2) photosensiti...

Photosensitized cleavage of some olefins as potential linkers to be used in drug delivery

NASA Astrophysics Data System (ADS)

Dinache, Andra; Smarandache, Adriana; Simon, Agota; Nastasa, Viorel; Tozar, Tatiana; Pascu, Alexandru; Enescu, Mironel; Khatyr, Abderrahim; Sima, Felix; Pascu, Mihail-Lucian; Staicu, Angela

2017-09-01

A study of photosensitized cleavage of different olefins as potential linkers for drug carrier complexes is reported. The role of singlet oxygen and the kinetic rates for light induced reactions were estimated by time-resolved measurements of singlet oxygen phosphorescence (at 1270 nm) obtained via 532 nm pulse laser excitation of a photosensitizer. The mixture of each studied olefin with verteporfin (used as photosensitizer) were exposed to low energy visible radiation. The rate constants for singlet oxygen quenching by studied olefins were determined. The irradiated solutions were investigated by FTIR spectroscopy and potential photoproducts were suggested. The experimental results were compared with simulations made by DFT method.

Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry

NASA Astrophysics Data System (ADS)

Pogue, Brian W.; Paulsen, Keith D.; O'Hara, Julia A.; Hoopes, P. Jack; Swartz, Harold

2000-03-01

Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

Oxygen evolution from BF3/MnO4-.

PubMed

Yiu, Shek-Man; Man, Wai-Lun; Wang, Xin; Lam, William W Y; Ng, Siu-Mui; Kwong, Hoi-Ki; Lau, Kai-Chung; Lau, Tai-Chu

2011-04-14

MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.

Photosensitization of Intact Heart Mitochondria by the Phthalocyanine Pc 4: Correlation of Structural and Functional Deficits with Cytochrome c Release

PubMed Central

Kim, Junhwan; Fujioka, Hisashi; Oleinick, Nancy L.; Anderson, Vernon E.

2010-01-01

Singlet oxygen is produced by absorption of red light by the phthalocyanine dye, Pc 4, followed by energy transfer to dissolved triplet oxygen. Mitochondria pre-incubated with Pc 4 were illuminated by red light and the damage to mitochondrial structure and function by the generated singlet oxygen was studied. At early illumination times (3–5 min. of red light exposure), state 3 respiration was inhibited (50%) while state 4 activity increased, resulting in effectively complete uncoupling. Individual complex activities were measured and only complex IV activity was significantly reduced and exhibited a dose response while the activities of electron transport complexes I, II and III were not significantly affected. Cyt c release was an increasing function of irradiation time with 30% being released following 5 min. of illumination. Mitochondrial expansion along with changes in the structure of the cristae were observed by transmission electron microscopy following 5 min. of irradiation with an increase of large vacuoles and membrane rupture occurring following more extensive exposures. PMID:20510354

Attaching naphthalene derivatives onto BODIPY for generating excited triplet state and singlet oxygen: Tuning PET-based photosensitizer by electron donors

NASA Astrophysics Data System (ADS)

Zhang, Xian-Fu; Feng, Nan

2018-01-01

meso-Naphthalene substituted BODIPY compounds were prepared in a facile one pot reaction. The naphthalene functionalization of BODIPY leads up to a 5-fold increase in the formation efficiency of excited triplet state and singlet oxygen in polar solvents. Steady state and time resolved fluorescence, laser flash photolysis, and quantum chemistry methods were used to reveal the mechanism. All measured data and quantum chemical results suggest that these systems can be viewed as electron donor-acceptor (D-A) pair (BODIPY acts as the acceptor), photoinduced charge transfer (PCT) or photoinduced electron transfer (PET) occurs upon photo excitation (D-A + hν → Dδ +-Aδ -, 0 < δ ≤ 1), and the charge recombination induced the formation of triplet state (Dδ +-Aδ - → D-A (T1). These novel PCT- or PET-based photosensitizers (PSs) show different features from traditional PSs, such as the strong tunability by facile structural modification and good selectivity upon medium polarity. The new character for this type of PSs can lead to important applications in organic oxygenation reactions and photodynamic therapy of tumors.

Calculation of singlet oxygen formation from one photon absorbing photosensitizers used in PDT

NASA Astrophysics Data System (ADS)

Potasek, M.; Parilov, Evgueni; Beeson, K.

2013-03-01

Advances in biophotonic medicine require new information on photodynamic mechanisms. In photodynamic therapy (PDT), a photosensitizer (PS) is injected into the body and accumulates at higher concentrations in diseased tissue compared to normal tissue. The PS absorbs light from a light source and generates excited-state triplet states of the PS. The excited triplet states of the PS can then react with ground state molecular oxygen to form excited singlet - state oxygen or form other highly reactive species. The reactive species react with living cells, resulting in cel l death. This treatment is used in many forms of cancer including those in the prostrate, head and neck, lungs, bladder, esophagus and certain skin cancers. We developed a novel numerical method to model the photophysical and photochemical processes in the PS and the subsequent energy transfer to O2, improving the understanding of these processes at a molecular level. Our numerical method simulates light propagation and photo-physics in PS using methods that build on techniques previously developed for optical communications and nonlinear optics applications.

Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

PubMed

Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

2016-09-01

Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

Multifunctional Micelles Dually Responsive to Hypoxia and Singlet Oxygen: Enhanced Photodynamic Therapy via Interactively Triggered Photosensitizer Delivery.

PubMed

Li, Juanjuan; Meng, Xuan; Deng, Jian; Lu, Di; Zhang, Xin; Chen, Yanrui; Zhu, Jundong; Fan, Aiping; Ding, Dan; Kong, Deling; Wang, Zheng; Zhao, Yanjun

2018-05-23

Nanoparticulate antitumor photodynamic therapy (PDT) has been suffering from the limited dose accumulation in tumor. Herein, we report dually hypoxia- and singlet oxygen-responsive polymeric micelles to efficiently utilize the photosensitizer deposited in the disease site and hence facilely improve PDT's antitumor efficacy. Tailored methoxy poly(ethylene glycol)-azobenzene-poly(aspartic acid) copolymer conjugate with imidazole as the side chains was synthesized. The conjugate micelles (189 ± 19 nm) obtained by self-assembly could efficiently load a model photosensitizer, chlorin e6 (Ce6) with a loading of 4.1 ± 0.5% (w/w). The facilitated cellular uptake of micelles was achieved by the triggered azobenzene collapse that provoked poly(ethylene glycol) shedding; rapid Ce6 release was enabled by imidazole oxidation that induced micelle disassembly. In addition, the singlet oxygen-mediated cargo release not only addressed the limited diffusion range and short half-life of singlet oxygen but also decreased the oxygen level, which could in turn enhance internalization and increase the intracellular Ce6 concentration. The hypoxia-induced dePEGylation and singlet oxygen-triggered Ce6 release was demonstrated both in aqueous buffer and in Lewis lung carcinoma (LLC) cells. The cellular uptake study demonstrated that the dually responsive micelles could deliver significantly more Ce6 to the cells, which resulted in a substantially improved cytotoxicity. This concurred well with the superior in vivo antitumor ability of micelles in a LLC tumor-bearing mouse model. This study presented an intriguing nanoplatform to realize interactively triggered photosensitizer delivery and improved antitumor PDT efficacy.

Dose-dependent photochemical/photothermal toxicity of indocyanine green-based therapy on three different cancer cell lines.

PubMed

Ruhi, Mustafa Kemal; Ak, Ayşe; Gülsoy, Murat

2018-03-01

The Food and Drug Administration-approved Indocyanine Green can be used as a photosensitizer to kill cancer cells selectively. Although indocyanine green is advantageous as a photosensitizer in terms of strong absorption in the near-infrared region, indocyanine green-based cancer treatment is still not approved as a clinical method. Some reasons for this are aggregation at high concentrations, rapid clearance of the photosensitizer from the body, low singlet oxygen quantum yield, and the uncertainty concerning its action mechanism. This in vitro study focuses on two of these points: "what is the cell inhibition mechanism of indocyanine green-based therapy?" and "how the dose-dependent aggregation problem of indocyanine green alters its cell inhibition efficiency?" The following experiments were conducted to provide insight into these points. Nontoxic doses of indocyanine green and near-infrared laser were determined. The aggregation behavior of indocyanine green was verified through experiments. The singlet oxygen quantum yield of indocyanine green at different concentrations were calculated. Various indocyanine green and energy densities of near-infrared light were applied to prostate cancer, neuroblastoma, and colon cancer cells. An MTT assay was performed at the end of the first, second, and third days following the treatments to determine the cell viability. Temperature changes in the medium during laser exposure were recorded. ROS generation following the treatment was verified by using a Total Reactive Oxygen Species detection kit. An apoptosis detection test was performed to establish the cell death mechanism and, finally, the cellular uptakes of the three different cells were measured. According to the results, indocyanine green-based therapy causes cell viability decrease for three cancer cell lines by means of excessive reactive oxygen species production. Different cells have different sensitivities to the therapy possibly because of the differentiation level and structural differences. The singlet oxygen generation of indocyanine green decreases at high concentrations because of aggregation. Nevertheless, better cancer cell killing effect was observed at higher photosensitizer concentrations. This result reveals that the cellular uptake of indocyanine green was determinant for better cancer cell inhibition. Copyright © 2018 Elsevier B.V. All rights reserved.

Singlet Oxygen at the Laundromat

NASA Astrophysics Data System (ADS)

Keeports, David

1995-09-01

Singlet molecular oxygen is an interesting molecule both visually and theoretically, since its red chemiluminescence can be analyzed by the application of simple molecular orbital theory. It can be produced from the reaction of hydrogen peroxide from either chlorine gas or hypochlorite ion from household bleach. Here we demostrate how to produce it using simple laundry cleansers.

A Classic Near-Infrared Probe Indocyanine Green for Detecting Singlet Oxygen.

PubMed

Tang, Cheng-Yi; Wu, Feng-Yao; Yang, Min-Kai; Guo, Yu-Min; Lu, Gui-Hua; Yang, Yong-Hua

2016-02-06

The revelation of mechanisms of photodynamic therapy (PDT) at the cellular level as well as singlet oxygen (¹O₂) as a second messengers requires the quantification of intracellular ¹O₂. To detect singlet oxygen, directly measuring the phosphorescence emitted from ¹O₂ at 1270 nm is simple but limited for the low quantum yield and intrinsic efficiency of ¹O₂ emission. Another method is chemically trapping ¹O₂ and measuring fluorescence, absorption and Electron Spin Resonance (ESR). In this paper, we used indocyanine green (ICG), the only near-infrared (NIR) probe approved by the Food and Drug Administration (FDA), to detect ¹O₂ in vitro. Once it reacts with ¹O₂, ICG is decomposed and its UV absorption at 780 nm decreases with the laser irradiation. Our data demonstrated that ICG could be more sensitive and accurate than Singlet Oxygen Sensor Green reagent(®) (SOSG, a commercialized fluorescence probe) in vitro, moreover, ICG functioned with Eosin Y while SOSG failed. Thus, ICG would reasonably provide the possibility to sense ¹O₂ in vitro, with high sensitivity, selectivity and suitability to most photosensitizers.

The low photo-inactivation rate of bacteria in human plasma II. Inhibition of methylene blue bleaching in plasma and effective bacterial destruction by the addition of dilute acetic acid to human plasma.

PubMed

Chen, Jie; Cesario, Thomas C; Li, Runze; Er, Ali O; Rentzepis, Peter M

2015-10-01

Methylene blue (MB) and other photo-sensitizer molecules have been recognized as effective means for the inactivation of bacteria and other pathogens owing to their ability to photo-generate reactive oxygen species (ROS) including singlet oxygen. These reactive species react with the membrane of the bacteria causing their destruction. However, the efficiency of MB to destroy bacteria in plasma is very low because the MB 660 nm absorption band, that is responsible for the ROS generation, is bleached. The bleaching of MB, in plasma, is caused by the attachment of a hydrogen atom to the central ring nitrogen of MB, which destroys the ring conjugation and forms Leuco-MB which does not absorb in the 600 nm region. In this paper we show that addition of dilute acetic acid, ∼10(-4) M, to human plasma, prevents H-atom attachment to MB, allowing MB to absorb at 660 nm, generates singlet oxygen and thus inactivates bacteria. The mechanism proposed, for preventing MB bleaching in plasma, is based on the oxidation of cysteine to cystine, by reaction with added dilute acetic acid, thus eliminating the availability of the thiol hydrogen atom which attaches to the MB nitrogen. It is expected that the addition of acetic acid to plasma will be effective in the sterilization of plasma and killing of bacteria in wounds and burns.

Physics and chemistry of the influence of excited molecules on combustion enhancement

PubMed Central

Starik, A. M.; Loukhovitski, B. I.; Sharipov, A. S.; Titova, N. S

2015-01-01

The paper addresses detailed analysis of kinetic processes in the H2−O2, CO−O2 and CH4−O2-reactive systems upon the presence of singlet oxygen molecules O2(a1Δg) and and the influence of the activation of oxygen molecules in electric discharge on the acceleration of ignition in the H2−O2 and CH4−O2 mixtures. The possibility of the intensification of CO oxidation due to excitation of O2 and N2 molecule vibrations and generation of singlet oxygen molecules is also considered. It is shown that the effect of accelerating the ignition strongly depends on the reduced electric field and, as a consequence, on the composition of discharge plasma as well as on the features of chain mechanism development in oxy-fuel systems. It is revealed that the most effective approach for the intensification of CO oxidation both in the moist air and in the products of hydrocarbon combustion in air is the generation of O2(a1Δg) molecules by electric discharge. Computations showed that the presence of 1% O2(a1Δg) in the total oxygen allowed one to convert CO to CO2 even at the temperature T=850–900 K in the time of 10−2 s. The excitation of O2 and N2 molecule vibrations is less effective for such a conversion. PMID:26170425

Photo-induced Leishmania DNA degradation by silver-doped zinc oxide nanoparticle: an in-vitro approach.

PubMed

Nadhman, Akhtar; Sirajuddin, Muhammad; Nazir, Samina; Yasinzai, Masoom

2016-06-01

Recently, the authors reported newly synthesised polyethylene glycol (PEG)ylated silver (9%)-doped zinc oxide nanoparticle (doped semiconductor nanoparticle (DSN)) which has high potency for killing Leishmania tropica by producing reactive oxygen species on exposure to sunlight. The current report is focused on Leishmania DNA interaction and damage caused by the DSN. Here, we showed that the damage to Leishmania DNA was indirect, as the DSN was unable to interact with the DNA in intact Leishmania cell, indicating the incapability of PEGylated DSN to cross the nucleus barrier. The DNA damage was the result of high production of singlet oxygen on exposure to sunlight. The DNA damage was successfully prevented by singlet oxygen scavenger (sodium azide) confirming involvement of the highly energetic singlet oxygen in the DNA degradation process.

Investigating the impact of oxygen concentration and blood flow variation on photodynamic therapy

NASA Astrophysics Data System (ADS)

Penjweini, Rozhin; Kim, Michele M.; Finlay, Jarod C.; Zhu, Timothy C.

2016-03-01

Type II photodynamic therapy (PDT) is used for cancer treatment based on the combined action of a photosensitizer, a special wavelength of light, oxygen (3O2) and generation of singlet oxygen (1O2). Intra-patient and inter-patient variability of oxygen concentration ([3O2]) before and after the treatment as well as photosensitizer concentration and hemodynamic parameters such as blood flow during PDT has been reported. Simulation of these variations is valuable, as it would be a means for the rapid assessment of treatment effect. A mathematical model has been previously developed to incorporate the diffusion equation for light transport in tissue and the macroscopic kinetic equations for simulation of [3O2], photosensitizers in ground and triplet states and concentration of the reacted singlet oxygen ([1O₂]rx) during PDT. In this study, the finite-element based calculation of the macroscopic kinetic equations is done for 2-(1- Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH)-mediated PDT by incorporating the information of the photosensitizer photochemical parameters as well as the tissue optical properties, photosensitizer concentration, initial oxygen concentration ([3O2]0), blood flow changes and Φ that have been measured in mice bearing radiation-induced fibrosarcoma (RIF) tumors. Then, [1O2]rx calculated by using the measured [3O2] during the PDT is compared with [1O2]rx calculated based on the simulated [3O₂]; both calculations showed a reasonably good agreement. Moreover, the impacts of the blood flow changes and [3O2]0 on [1O2]rx have been investigated, which showed no pronounced effect of the blood flow changes on the long-term 1O2 generation. When [3O2]0 becomes limiting, small changes in [3O₂] have large effects on [1O2]rx.

Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation.

PubMed

Varchola, Jaroslav; Huntosova, Veronika; Jancura, Daniel; Wagnières, Georges; Miskovsky, Pavol; Bánó, Gregor

2014-12-01

Assessment of partial pressure of oxygen (pO2) by luminescence lifetime measurements of ruthenium coordination complexes has been studied intensively during the last few decades. RuPhen (dichlorotris(1,10-phenanthroline) ruthenium(ii) hydrate) is a water soluble molecule that has been tested previously for in vivo pO2 detection. In this work we intended to shed light on the production of singlet oxygen by RuPhen. The quantum yield of singlet oxygen production by RuPhen dissolved in 0.9% aqueous NaCl solution (pH = 6) was measured at physiological temperatures (285-310 K) and various concentrations of molecular oxygen. In order to minimize the bleaching of RuPhen, the samples were excited with low power (<2 mW) laser pulses (20 μs long), created by pulsing a cw laser beam with an acousto-optical modulator. We show that, whereas the RuPhen phosphorescence lifetime decreases rapidly with an increase of temperature (keeping the oxygenation level constant), the quantum yield of singlet oxygen production by RuPhen is almost identical in the temperature range of 285-310 K. For air-saturated conditions at 310 K the measured quantum yield is about 0.25. The depopulation rate constants of the RuPhen (3)MLCT (metal-to-ligand charge-transfer) state are determined in the absence and in the presence of oxygen. We determined that the excitation energy for the RuPhen (3)MLCT→d-d transition is 49 kJ mol(-1) in the 0.9% NaCl solution (pH = 6).

Photooxidation of d(TpG) by phthalocyanines and riboflavin. Isolation and characterization of dinucleoside monophosphates containing the 4R* and 4S* diastereoisomers of 4,8-dihydro-4-hydroxy-8-oxo-2'-deoxy-guanosine.

PubMed Central

Buchko, G W; Cadet, J; Berger, M; Ravanat, J L

1992-01-01

Phthalocyanine mediated photosensitization of 2'-deoxyguanosine (dG) in oxygen saturated aqueous solution has previously been shown to result in the addition of molecular oxygen to the guanine base generating the 4R* and 4S* diastereoisomers of 4,8-dihydro-4-hydroxy-8-oxo-2'-deoxyguanosine (dO) (the asterisk denotes unambiguous assignment of the 4R and 4S diastereoisomers). The data presented here show that the same guanine modified bases are generated in a 1:1 ratio when thymidylyl-(3',5')-2'-deoxyguanosine (d(TpG)) is similarly photo-oxidized. These modified dinucleoside monophosphates, labelled d(TpO)-A and -B, have been isolated by high performance liquid chromatography and characterized by proton NMR spectrometry, fast atom bombardment mass spectrometry, and enzymatic digestions. Photosensitization in D2O instead of H2O leads to an increase in the rate of d(TpO) formation that is consistent with a type II (singlet oxygen) reaction mechanism. Three interesting properties of these modified dinucleoside monophosphates are: i) the rate of their digestion with spleen phosphodiesterase is greatly reduced relative to d(TpG), ii) they are not digested by snake venom phosphodiesterase, and iii) they are stable to 1.0 M piperidine at 90 degrees C for 30 min. The latter observation indicates that 4,8-dihydro-4-hydroxy-8-oxoguanine is not a base lesion responsible for the strand breaks observed following hot piperidine treatment of DNA exposed to type II photosensitizers or chemically generated singlet oxygen. PMID:1329029

Photophysics of covalently functionalized single wall carbon nanotubes with verteporfin

NASA Astrophysics Data System (ADS)

Staicu, Angela; Smarandache, Adriana; Pascu, Alexandru; Pascu, Mihail Lucian

2017-09-01

Covalently functionalized single wall carbon nanotubes (SWCNT) with the photosensitizer verteporfin (VP) were synthesized and studied. Photophysical properties of the obtained compounds like optical absorption, laser-induced fluorescence and generated singlet oxygen were investigated. In order to highlight the features of the conjugated compound, its photophysical characteristics were compared with those of the mixtures of the initial components. The optical absorption data evidenced a compound that combines features of the primary SWCNTs and VP. This is the also the case of the laser induced fluorescence of the synthesized product. Moreover, fluorescence quantum yield (Φf) of the compound (Φf = 2.4%) is smaller than for the mixture of SWCNT and VP in (Φf = 3.2%). The behavior is expected, because linked VP (carrying the fluorescent moiety) transfers easier a part of its excitation energy to the SWCNT in the covalent structure. Relative to the quantum yield of singlet oxygen generation (ΦΔ) by Methylene Blue, it was found that the ΦΔ for the conjugated VP-SWCNT is 51% while for the mixture ΦΔ is 23%. The results indicate covalently functionalized single walled carbon nanotubes with verteporfin as potential compounds of interest in targeted drug delivery and photodynamic therapy.

T-Opt: A 3D Monte Carlo simulation for light delivery design in photodynamic therapy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Honda, Norihiro; Hazama, Hisanao; Awazu, Kunio

2017-02-01

The interstitial photodynamic therapy (iPDT) with 5-aminolevulinic acid (5-ALA) is a safe and feasible treatment modality of malignant glioblastoma. In order to cover the tumour volume, the exact position of the light diffusers within the lesion is needed to decide precisely. The aim of this study is the development of evaluation method of treatment volume with 3D Monte Carlo simulation for iPDT using 5-ALA. Monte Carlo simulations of fluence rate were performed using the optical properties of the brain tissue infiltrated by tumor cells and normal tissue. 3-D Monte Carlo simulation was used to calculate the position of the light diffusers within the lesion and light transport. The fluence rate near the diffuser was maximum and decreased exponentially with distance. The simulation can calculate the amount of singlet oxygen generated by PDT. In order to increase the accuracy of simulation results, the parameter for simulation includes the quantum yield of singlet oxygen generation, the accumulated concentration of photosensitizer within tissue, fluence rate, molar extinction coefficient at the wavelength of excitation light. The simulation is useful for evaluation of treatment region of iPDT with 5-ALA.

A quantum protective mechanism in photosynthesis

NASA Astrophysics Data System (ADS)

Marais, Adriana; Sinayskiy, Ilya; Petruccione, Francesco; van Grondelle, Rienk

2015-03-01

Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is observed to be reduced by weak magnetic fields. Reaction centres from plants' photosystem II share many features with bacterial reaction centres, including a high-spin iron whose function has remained obscure. To explain observations that the magnetic field effect is reduced by the iron, we propose that its fast-relaxing spin plays a protective role in photosynthesis by generating an effective magnetic field. We consider a simple model of the system, derive an analytical expression for the effective magnetic field and analyse the resulting triplet yield reduction. The protective mechanism is robust for realistic parameter ranges, constituting a clear example of a quantum effect playing a macroscopic role vital for life.

A quantum protective mechanism in photosynthesis.

PubMed

Marais, Adriana; Sinayskiy, Ilya; Petruccione, Francesco; van Grondelle, Rienk

2015-03-03

Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is observed to be reduced by weak magnetic fields. Reaction centres from plants' photosystem II share many features with bacterial reaction centres, including a high-spin iron whose function has remained obscure. To explain observations that the magnetic field effect is reduced by the iron, we propose that its fast-relaxing spin plays a protective role in photosynthesis by generating an effective magnetic field. We consider a simple model of the system, derive an analytical expression for the effective magnetic field and analyse the resulting triplet yield reduction. The protective mechanism is robust for realistic parameter ranges, constituting a clear example of a quantum effect playing a macroscopic role vital for life.

Photosensitized degradation of losartan potassium in an extemporaneous suspension formulation.

PubMed

Seburg, Randal A; Ballard, John M; Hwang, Tsang-Lin; Sullivan, Caitlin M

2006-10-11

During development of an extemporaneous suspension formulation for losartan potassium, previously unknown degradation products were observed in experimental suspensions prepared in a commercial cherry syrup vehicle. These degradates increased rapidly when analytical solutions prepared from that suspension were exposed to ambient light. The structures of the degradates were determined using a combination of preparative HPLC, LC/MS, (13)C and (1)H NMR (1D and 2D), and mechanistic chemistry. Each degradate results from destruction of the imidazole ring of losartan. Formation of the two major degradates required exposure to light (UV or visible) and the presence of oxygen. Experiments using Rose Bengal (a singlet oxygen photosensitizer) and 1,4-diazabicyclooctane (DABCO; a singlet oxygen quencher) established that the major photodegradates are formed via the intermediacy of singlet oxygen. The identity of the photosensitizer in the formulation was not unequivocally determined; however, the experiments implicated the artificial flavoring in fulfilling this role.

Effects of various chemical compounds on spontaneous and hydrogen peroxide-induced reversion in strain TA104 of Salmonella typhimurium.

PubMed

Han, J S

1992-04-01

In experiments designed to determine which active oxygen species contribute to hydrogen peroxide (HP)-induced reversion in strain TA104 of Salmonella typhimurium, 1,10-phenanthroline (an iron chelator, which prevents the formation of hydroxyl radicals from HP and DNA-bound iron by the Fenton reaction), sodium azide (a singlet oxygen scavenger), and potassium iodide (an hydroxyl radical scavenger) inhibited HP-induced reversion. These results indicate that hydroxyl radicals generated from HP by the Fenton reaction, and perhaps singlet oxygen, contribute to HP-induced reversion in TA104. However, reduced glutathione (reduces Fe3+ to Fe2+ and/or HP to water), diethyldithiocarbamic acid (an inhibitor of superoxide dismutase), diethyl maleate (a glutathione scavenger), and 3-amino-1,2,4-triazole (an inhibitor of catalase) did not inhibit HP-induced reversion in TA104. Thus, superoxide radical anions and HP itself do not appear to be the cause of HP-induced reversion in this strain. In experiments on the effect of 5 common dietary compounds (beta-carotene, retinoic acid, and vitamins A, C and E), chlorophyllin (CHL), and ergothioneine, the frequency of revertants in TA104 increased above the spontaneous frequency in the presence of beta-carotene or vitamin C (about 2-fold) or vitamin A (about 3-fold). The 5 dietary antimutagens and CHL did not inhibit HP-induced reversion in TA104. However, L-ergothioneine inhibited HP-induced reversion in this strain. Therefore, it is likely that L-ergothioneine is a scavenger of hydroxyl radicals or an inhibitor of their formation, and perhaps of singlet oxygen, at the concentrations tested in TA104.

CHEMISTRY OF FOG WATERS IN CALIFORNIA'S CENTRAL VALLEY: 1. IN SITU PHOTOFORMATION OF HYDROXYL RADICAL AND SINGLET MOLECULAR OXYGEN. (R825433)

EPA Science Inventory

The aqueous-phase photoformation of hydroxyl radical (OH) and singlet molecular oxygen (O₂(¹Δ_g) or ¹O^*

Antitumor effects evaluation of a novel porphyrin derivative in photodynamic therapy.

PubMed

Li, Jian-Wei; Wu, Zhong-Ming; Magetic, Davor; Zhang, Li-Jun; Chen, Zhi-Long

2015-12-01

In this paper, the antitumor activity of a novel porphyrin-based photosensitizer 5,10,15,20-tetrakis[(5-diethylamino)pentyl] porphyrin (TDPP) was reported in vitro and in vivo. The photophysical and cellular properties of TDPP were investigated. The singlet oxygen generation quantum yield of TDPP was detected; it showed a high singlet oxygen quantum yield of 0.52. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The efficiency of TDPP-photodynamic therapy (PDT) in vitro was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and in situ trypan blue exclusion test. Treated with a 630-nm laser, TDPP can kill cultured human esophageal cancer cell line (Eca-109) cells and reduce the growth of Eca-109 xenograft tumors significantly in BABL/c nude mice. And histopathological study was also used to confirm the antitumor effect. It has the perspective to be developed as a new antitumor drug in photodynamic therapy and deserves further investigation.

[Influence of CNTs on Photodegradation of Salbutamol in Water Environment].

PubMed

Wang, Qi; Han, Jia-rui; Wei, Bo-fan; Zhou, Lei; Zhang, Ya; Yang, Xi

2015-08-01

The influence of CNTs on the photolysis of organic pollutant was investigated by studying the photodegradation kinetics of SAL under 1000 W Xenon lamp, in the presence of three kinds of CNTs (SCNT, MWNT-COOH, MWNT-OH). In addition, the interaction between CNTs and Fe3" was also investigated. The results showed that the photodegradation of salbutamol followed pseudo-first-order kinetics, which could be inhibited by all three kinds of CNTs through light screening effect. Formation of singlet oxygen was detected during the photolysis, using the molecular probe furfuryl alcohol. All three kinds of CNTs could absorb electrons through competition, i.e., inhibit SAL photodegradation by light screening effect; meanwhile, the CNTs could generate singlet oxygen through photoexcitation to promote the photodegradation reaction. Both mechanisms coexisted, and in most cases, the inhibition effect was dominant. In addition, CNTs could inactivate the photoactive substance Fe3 in the water body by electrostatic adsorption, and affect the photochemical behavior of organic pollutants in natural water body.

Macroscopic singlet oxygen model incorporating photobleaching as an input parameter

NASA Astrophysics Data System (ADS)

Kim, Michele M.; Finlay, Jarod C.; Zhu, Timothy C.

2015-03-01

A macroscopic singlet oxygen model for photodynamic therapy (PDT) has been used extensively to calculate the reacted singlet oxygen concentration for various photosensitizers. The four photophysical parameters (ξ, σ, β, δ) and threshold singlet oxygen dose ([1O2]r,sh) can be found for various drugs and drug-light intervals using a fitting algorithm. The input parameters for this model include the fluence, photosensitizer concentration, optical properties, and necrosis radius. An additional input variable of photobleaching was implemented in this study to optimize the results. Photobleaching was measured by using the pre-PDT and post-PDT sensitizer concentrations. Using the RIF model of murine fibrosarcoma, mice were treated with a linear source with fluence rates from 12 - 150 mW/cm and total fluences from 24 - 135 J/cm. The two main drugs investigated were benzoporphyrin derivative monoacid ring A (BPD) and 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH). Previously published photophysical parameters were fine-tuned and verified using photobleaching as the additional fitting parameter. Furthermore, photobleaching can be used as an indicator of the robustness of the model for the particular mouse experiment by comparing the experimental and model-calculated photobleaching ratio.

Methods of Functionalization of Carbon Nanotubes by Photooxidation

NASA Technical Reports Server (NTRS)

Lebron-Colon, Marisabel (Inventor); Meador, Michael A. (Inventor)

2016-01-01

A method of photooxidizing carbon nanotubes, such as single-walled and multi-walled carbon nanotubes. The nanotubes are purified and dispersed in a solvent, such as n-methyl pyrrolidinone or dimethylformamide. A singlet oxygen sensitizer like Rose Bengal is added to the solution. Oxygen gas is continuously supplied while irradiating the solution while irradiating the solution with ultraviolet light to produce singlet oxygen to oxidize the single-walled carbon nanotubes. Advantageously, the method significantly increases the level of oxidation compared with prior art methods.

Observation of oscillatory surface reactions of riboflavin, trolox, and singlet oxygen using single carbon nanotube fluorescence spectroscopy.

PubMed

Sen, Fatih; Boghossian, Ardemis A; Sen, Selda; Ulissi, Zachary W; Zhang, Jingqing; Strano, Michael S

2012-12-21

Single-molecule fluorescent microscopy allows semiconducting single-walled carbon nanotubes (SWCNTs) to detect the adsorption and desorption of single adsorbate molecules as a stochastic modulation of emission intensity. In this study, we identify and assign the signature of the complex decomposition and reaction pathways of riboflavin in the presence of the free radical scavenger Trolox using DNA-wrapped SWCNT sensors dispersed onto an aminopropyltriethoxysilane (APTES) coated surface. SWCNT emission is quenched by riboflavin-induced reactive oxygen species (ROS), but increases upon the adsorption of Trolox, which functions as a reductive brightening agent. Riboflavin has two parallel reaction pathways, a Trolox oxidizer and a photosensitizer for singlet oxygen and superoxide generation. The resulting reaction network can be detected in real time in the vicinity of a single SWCNT and can be completely described using elementary reactions and kinetic rate constants measured independently. The reaction mechanism results in an oscillatory fluorescence response from each SWCNT, allowing for the simultaneous detection of multiple reactants. A series-parallel kinetic model is shown to describe the critical points of these oscillations, with partition coefficients on the order of 10(-6)-10(-4) for the reactive oxygen and excited state species. These results highlight the potential for SWCNTs to characterize complex reaction networks at the nanometer scale.

Time-resolved singlet-oxygen luminescence detection with an efficient and practical semiconductor single-photon detector

PubMed Central

Boso, Gianluca; Ke, Damei; Korzh, Boris; Bouilloux, Jordan; Lange, Norbert; Zbinden, Hugo

2015-01-01

In clinical applications, such as PhotoDynamic Therapy, direct singlet-oxygen detection through its luminescence in the near-infrared range (1270 nm) has been a challenging task due to its low emission probability and the lack of suitable single-photon detectors. Here, we propose a practical setup based on a negative-feedback avalanche diode detector that is a viable alternative to the current state-of-the art for different clinical scenarios, especially where geometric collection efficiency is limited (e.g. fiber-based systems, confocal microscopy, scanning systems etc.). The proposed setup is characterized with Rose Bengal as a standard photosensitizer and it is used to measure the singlet-oxygen quantum yield of a new set of photosensitizers for site-selective photodynamic therapy. PMID:26819830

Photodynamic Modification Of Plasma Membrane Function In Erythrocytes Sensitized By Xanthenes: What Determines Potency?

NASA Astrophysics Data System (ADS)

Pooler, John P.

1988-02-01

Several xanthene sensitizers were compared as sensitizers of membrane function in erythrocytes and some of their physico-chemical properties were examined. Eosin derivatives that localize at different membrane sites were equally effective at sensitizing both ion leaks and inactivation of membrane cholinesterase, implying that a diffusible intermediate reacts with membrane targets. Assessments of membrane loading and calculations of diffusion distances for singlet oxygen indicate that amounts of membrane-located sensitizer are quantitatively much greater than amounts in the nearby reaction medium. Potency measurements and assessment of absorption spectra and singlet oxygen production in water-dioxane mixtures lead to the conclusion that differential sorption to membranes, photon capture in low polarity environments and conversion of excited states to singlet oxygen are they key determinants of sensitizing potency.

A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases.

PubMed

Petrou, Athinoula L; Terzidaki, Athina

2017-08-02

From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG ≠ values that vary in the range 92.8-127 kJ mol -1 at 310 K. A value of ∼10-30 kJ mol -1 is the activation energy for the diffusion of reactants, depending on the reaction and the medium. The energy needed for the excitation of O 2 from the ground to the first excited state ( 1 Δ g , singlet oxygen) is equal to 92 kJ mol -1 So, the ΔG ≠ is equal to the energy needed for the excitation of ground state oxygen to the singlet oxygen ( 1 Δ g first excited) state. The similarity of the ΔG ≠ values is an indication that a common mechanism in the above disorders may be taking place. We attribute this common mechanism to the (same) role of the oxidative stress and specifically of singlet oxygen, ( 1 Δ g ), to the above-mentioned processes: excitation of ground state oxygen to the singlet oxygen, 1 Δ g , state (92 kJ mol -1 ), and reaction of the empty π* orbital with high electron density regions of biomolecules (∼10-30 kJ mol -1 for their diffusion). The ΔG ≠ for cases of heat-induced cell killing (cancer) lie also in the above range at 310 K. The present paper is a review and meta-analysis of literature data referring to neurodegenerative and other disorders. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

Transparent photocatalytic coatings on the surface of the tips of medical fibre-optic bundles

NASA Astrophysics Data System (ADS)

Evstropiev, S. K.; Volynkin, V. M.; Kiselev, V. M.; Dukelskii, K. V.; Evstropyev, K. S.; Demidov, V. V.; Gatchin, Yu. A.

2017-12-01

We report the results of the development of the sol - gel method for obtaining thin, transparent (in the visible part of the spectrum) TiO2/MgO coatings on the surfaces of the tips of medical fibre-optic bundles. Such coatings are capable of generating singlet oxygen under the action of UV radiation and are characterised by high antibacterial activity.

Near-Unity Quantum Yields for Intersystem Crossing and Singlet Oxygen Generation in Polymethine-like Molecules: Design and Experimental Realization

DTIC Science & Technology

2010-01-01

Florida, Cocoa , Florida 32922, ^Institute of Organic Chemistry, National Academy of Sciences, Kiev 03094, Ukraine, and #Physics and Optical Engineering...the time evolution of the S-S and T-Tabsorption and their cross sections (σSS and σTT). S-SandT-TESAspectra for SD-S7508are shown inFigure3a. SD-O

A laser unit for photodynamic therapy and robot-assisted microsurgery in dentistry

NASA Astrophysics Data System (ADS)

Chunikhin, A. A.; Bazikyan, E. A.; Pikhtin, N. A.

2017-06-01

Results are presented of photochemical experiments with an IR-laser unit for microsurgery and photodynamic therapy in dentistry. The efficiency of direct generation of singlet oxygen in model organic media in the continuous-wave and pulsed nanosecond modes is examined. The unit can serve both as an independent instrument and as a part of a complex for robot-assisted surgery and dentistry.

Limits in Proton Nuclear Singlet-State Lifetimes Measured with para-Hydrogen-Induced Polarization.

PubMed

Zhang, Yuning; Duan, Xueyou; Soon, Pei Che; Sychrovský, Vladimír; Canary, James W; Jerschow, Alexej

2016-10-05

The synthesis of a hyperpolarized molecule was developed, where the polarization and the singlet state were preserved over two controlled chemical steps. Nuclear singlet-state lifetimes close to 6 min for protons are reported in dimethyl fumarate. Owing to the high symmetry (AA'X 3 X 3 ' and A 2 systems), the singlet-state readout requires either a chemical desymmetrization or a long and repeated spin lock. Using DFT calculations and relaxation models, we further determine nuclear spin singlet lifetime limiting factors, which include the intramolecular dipolar coupling mechanism (proton-proton and proton-deuterium), the chemical shift anisotropy mechanism (symmetric and antisymmetric), and the intermolecular dipolar coupling mechanism (to oxygen and deuterium). If the limit of paramagnetic relaxation caused by residual oxygen could be lifted, the intramolecular dipolar coupling to deuterium would become the limiting relaxation mechanism and proton lifetimes upwards of 26 min could become available in the molecules considered here (dimethyl maleate and dimethyl fumarate). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysical dynamics of the efficient emission and photosensitization of [Ir(pqi)2(NN)]+ complexes.

PubMed

Zanoni, Kassio P S; Ito, Akitaka; Grüner, Malte; Murakami Iha, Neyde Y; de Camargo, Andrea S S

2018-01-23

The photophysical dynamics of three complexes in the highly-emissive [Ir(pqi) 2 (NN)] + series were investigated aiming at unique photophysical features and applications in light-emitting and singlet oxygen sensitizing research fields. Rational elucidation and Franck-Condon analyses of the observed emission spectra in nitrile solutions at 298 and 77 K reveal the true emissive nature of the lowest-lying triplet excited state (T 1 ), consisting of a hybrid 3 MLCT/LC Ir(pqi)→pqi state. Emissive deactivations from T 1 occur mainly by very intense, yellow-orange phosphorescence with high quantum yields and radiative rates. The emission nature experimentally verified is corroborated by theoretical calculations (TD-DFT), with T 1 arising from a mixing of several transitions induced by the spin-orbit coupling, majorly ascribed to 3 MLCT/LC Ir(pqi)→pqi and increasing contributions of 3 MLCT/LLCT Ir(pqi)→NN . The microsecond-lived emission of T 1 is rapidly quenched by molecular oxygen, with an efficient generation of singlet oxygen. Our findings show that the photophysics of [Ir(pqi) 2 (NN)][PF 6 ] complexes is suitable for many applications, from the active layer of electroluminescent devices to photosensitizers for photodynamic therapy and theranostics.

Phosphorescence dynamics of singlet oxygen and Radachlorin photosensitizer in aqueous solution

NASA Astrophysics Data System (ADS)

Belik, V. P.; Beltukova, D. M.; Gadzhiev, I. M.; Semenova, I. V.; Vasyutinskii, O. S.

2017-07-01

The luminescence spectrum of aqueous solution of Radachlorin photosensitizer in the near IR spectral range (950-1350 nm) has been determined at the excitation in both the Soret and Q absorption bands. Major sources of the recorded luminescence were analyzed. Kinetics of photosensitizer and singlet oxygen phosphorescence signals were studied by means of time-resolved spectroscopy. The corresponding characteristic lifetimes were determined.

Synthesis of {111} Facet-Exposed MgO with Surface Oxygen Vacancies for Reactive Oxygen Species Generation in the Dark.

PubMed

Hao, Ying-Juan; Liu, Bing; Tian, Li-Gang; Li, Fa-Tang; Ren, Jie; Liu, Shao-Jia; Liu, Ying; Zhao, Jun; Wang, Xiao-Jing

2017-04-12

Seeking a simple and moderate route to generate reactive oxygen species (ROS) for antibiosis is of great interest and challenge. This work demonstrates that molecule transition and electron rearrangement processes can directly occur only through chemisorption interaction between the adsorbed O 2 and high-energy {111} facet-exposed MgO with abundant surface oxygen vacancies (SOVs), hence producing singlet oxygen and superoxide anion radicals without light irradiation. These ROS were confirmed by electron paramagnetic resonance, in situ Raman, and scavenger experiments. Furthermore, heat plays a crucial role for the electron transfer process to accelerate the formation of ·O 2 - , which is verified by temperature kinetic experiments of nitro blue tetrazolium reduction in the dark. Therefore, the presence of oxygen vacancy can be considered as an intensification of the activation process. The designed MgO is acquired in one step via constructing a reduction atmosphere during the combustion reaction process, which has an ability similar to that of noble metal Pd to activate molecular oxygen and can be used as an effective bacteriocide in the dark.

Virus Capsids as Targeted Nanoscale Delivery Vessels of Photoactive Compounds for Site-Specific Photodynamic Therapy

NASA Astrophysics Data System (ADS)

Cohen, Brian A.

The research presented in this work details the use of a viral capsid as an addressable delivery vessel of photoactive compounds for use in photodynamic therapy. Photodynamic therapy is a treatment that involves the interaction of light with a photosensitizing molecule to create singlet oxygen, a reactive oxygen species. Overproduction of singlet oxygen in cells can cause oxidative damage leading to cytotoxicity and eventually cell death. Challenges with the current generation of FDA-approved photosensitizers for photodynamic therapy primarily stem from their lack of tissue specificity. This work describes the packaging of photoactive cationic porphyrins inside the MS2 bacteriophage capsid, followed by external modification of the capsid with cancer cell-targeting G-quadruplex DNA aptamers to generate a tumor-specific photosensitizing agent. First, a cationic porphyrin is loaded into the capsids via nucleotide-driven packaging, a process that involves charge interaction between the porphyrin and the RNA inside the capsid. Results show that over 250 porphyrin molecules associate with the RNA within each MS2 capsid. Removal of RNA from the capsid severely inhibits the packaging of the cationic porphyrins. Porphyrin-virus constructs were then shown to photogenerate singlet oxygen, and cytotoxicity in non-targeted photodynamic treatment experiments. Next, each porphyrin-loaded capsid is externally modified with approximately 60 targeting DNA aptamers by employing a heterobifunctional crosslinking agent. The targeting aptamer is known to bind the protein nucleolin, a ubiquitous protein that is overexpressed on the cell surface by many cancer cell types. MCF-7 human breast carcinoma cells and MCF-10A human mammary epithelial cells were selected as an in vitro model for breast cancer and normal tissue, respectively. Fluorescently tagged virus-aptamer constructs are shown to selectively target MCF-7 cells versus MCF-10A cells. Finally, results are shown in which porphyrin-virus-aptamer constructs selectively target and kill cancer cells versus non-cancer cells. Specifically, the results show that MS2 is a viable candidate as an addressable nanodelivery vessel of photoactive compounds, and the implications are that the nucleotide-driven packaging approach for modifying MS2 can be used to impart new functionalities for a host of diagnostic or therapeutic applications.

Silicon(IV) phthalocyanines substituted axially with different nucleoside moieties. Effects of nucleoside type on the photosensitizing efficiencies and in vitro photodynamic activities.

PubMed

Zheng, Bi-Yuan; Shen, Xiao-Min; Zhao, Dong-Mei; Cai, Yi-Bin; Ke, Mei-Rong; Huang, Jian-Dong

2016-06-01

A series of new silicon(IV) phthalocyanines (SiPcs) di-substituted axially with different nucleoside moieties have been synthesized and evaluated for their singlet oxygen quantum yields (ΦΔ) and in vitro photodynamic activities. The adenosine-substituted SiPc shows a lower photosensitizing efficiency (ΦΔ=0.35) than the uridine- and cytidine-substituted analogs (ΦΔ=0.42-0.44), while the guanosine-substituted SiPc exhibits a weakest singlet oxygen generation efficiency with a ΦΔ value down to 0.03. On the other hand, replacing axial adenosines with chloro-modified adenosines and purines can result in the increase of photogenerating singlet oxygen efficiencies of SiPcs. The formed SiPcs 1 and 2, which contain monochloro-modified adenosines and dichloro-modified purines respectively, appear as efficient photosensitizers with ΦΔ of 0.42-0.44. Both compounds 1 and 2 present high photocytotoxicities against HepG2 and BGC823 cancer cells with IC50 values ranging from 9nM to 33nM. The photocytotoxicities of these two compounds are remarkably higher than the well-known anticancer photosensitizer, chlorin e6 (IC50=752nM against HepG2 cells) in the same condition. As revealed by confocal microscopy, for both cell lines, compound 1 can essentially bind to mitochondria, while compound 2 is just partially localized in mitochondria. In addition, the two compounds induce cell death of HepG2 cells likely through apoptosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Photophysical and photochemical properties of Bauhinia megalandra (Caesalpinaceae) extracts as new PDT photosensitizer

NASA Astrophysics Data System (ADS)

Vargas Tovar, Franklin R.; Rivas, C.; Estrada, O.; Marcano O., Aristides A.; Echevarria, Lorenzo; Diaz, Yrene; Alexander, I.; Rodriguez, L.; Padron, L.; Rivera, I. R.

2004-10-01

Recently new photosensitizers, chlorophyll "a and b" derivatives, for photodynamic therapy (PDT) have been presented. It already passed complete pre-clinical investigations. This prompted us to carry out an extensive study of photophysical properties of chlorine derivatives, important both for optimization of their clinic applications and for study of mechanisms of chlorine PDT&. The fresh leaves of Bauhinia megalandra (Caesalpinaceae) were extracted with methanol by percolation, and re-extract with a mixture of methanol-water (1:1), the insoluble fraction was then separated by column chromatography [RP18/hexane-ethylacetate (9:1)] to obtain four fractions named 1 to 4. These compounds were identified by NMR data. We found that 3 and 4 efficiently generates singlet oxygen when irradiated with visible light. Detection of the singlet oxygen was fulfilled by its reaction with histidine and detected by bleaching p-nitrosodimethylaniline under 440 nm irradiation. The quantum yields of singlet oxygen determined by us were 0.088 (1), 0.151 (2), 0.219 (3) and 0.301 (4). We measured absorption and fluorescence spectra of compounds 1 to 4 (Mg-chlorophyll-a, Pheophytin, Mg-chlorophyll-b and chlorophyll-b respectively) in different media and in aqueous solutions of human serum albumin. The association constant of the compounds 1, 2, 3 and 4 in the presence of HSA were estimated. The binding and quenching studies suggest that only 1 and 3 may serve as a useful fluorescence probe for structure/function studies of different chlorophyll binding proteins. No photoinduced binding was observed after irradiation by all the studied compounds in presence of human serum albumin.

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

PubMed

Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

2017-04-06

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

Ultrasound-assisted interaction between chlorin-e6 and human serum albumin: pH dependence, singlet oxygen production, and formulation effect

NASA Astrophysics Data System (ADS)

Mocanu, Mihaela N.; Yan, Fei

2018-02-01

The interaction between chlorin e6 (Ce6) and human serum albumin (HSA) in the presence and absence of ultrasound have been investigated by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy. Ce6 is found to bind strongly to HSA at or near physiological pH conditions, but the strength of the binding is significantly weakened at lower pHs. The intrinsic fluorescence of HSA is incrementally quenched with increasing concentration of Ce6, and the quenching is enhanced after exposure to high-frequency ultrasound. Our experimental results suggest that Ce6-induced sonodynamic oxidation of HSA is mainly mediated by singlet oxygen. The formulation of Ce6 by high molecular weight polyvinylpyrrolidone (PVP) increased its stability in aqueous solutions and its quantum yield of singlet oxygen under ultrasound irradiation.

Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin.

PubMed

Dose, Janina; Matsugo, Seiichi; Yokokawa, Haruka; Koshida, Yutaro; Okazaki, Shigetoshi; Seidel, Ulrike; Eggersdorfer, Manfred; Rimbach, Gerald; Esatbeyoglu, Tuba

2016-01-14

Astaxanthin is a coloring agent which is used as a feed additive in aquaculture nutrition. Recently, potential health benefits of astaxanthin have been discussed which may be partly related to its free radical scavenging and antioxidant properties. Our electron spin resonance (ESR) and spin trapping data suggest that synthetic astaxanthin is a potent free radical scavenger in terms of diphenylpicryl-hydrazyl (DPPH) and galvinoxyl free radicals. Furthermore, astaxanthin dose-dependently quenched singlet oxygen as determined by photon counting. In addition to free radical scavenging and singlet oxygen quenching properties, astaxanthin induced the antioxidant enzyme paroxoanase-1, enhanced glutathione concentrations and prevented lipid peroxidation in cultured hepatocytes. Present results suggest that, beyond its coloring properties, synthetic astaxanthin exhibits free radical scavenging, singlet oxygen quenching, and antioxidant activities which could probably positively affect animal and human health.

Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin

PubMed Central

Dose, Janina; Matsugo, Seiichi; Yokokawa, Haruka; Koshida, Yutaro; Okazaki, Shigetoshi; Seidel, Ulrike; Eggersdorfer, Manfred; Rimbach, Gerald; Esatbeyoglu, Tuba

2016-01-01

Astaxanthin is a coloring agent which is used as a feed additive in aquaculture nutrition. Recently, potential health benefits of astaxanthin have been discussed which may be partly related to its free radical scavenging and antioxidant properties. Our electron spin resonance (ESR) and spin trapping data suggest that synthetic astaxanthin is a potent free radical scavenger in terms of diphenylpicryl-hydrazyl (DPPH) and galvinoxyl free radicals. Furthermore, astaxanthin dose-dependently quenched singlet oxygen as determined by photon counting. In addition to free radical scavenging and singlet oxygen quenching properties, astaxanthin induced the antioxidant enzyme paroxoanase-1, enhanced glutathione concentrations and prevented lipid peroxidation in cultured hepatocytes. Present results suggest that, beyond its coloring properties, synthetic astaxanthin exhibits free radical scavenging, singlet oxygen quenching, and antioxidant activities which could probably positively affect animal and human health. PMID:26784174

Pharmaceutical micelles featured with singlet oxygen-responsive cargo release and mitochondrial targeting for enhanced photodynamic therapy.

PubMed

Zhang, Xin; Yan, Qi; Mulatihan, Di Naer; Zhu, Jundong; Fan, Aiping; Wang, Zheng; Zhao, Yanjun

2018-06-22

The efficacy of nanoparticulate photodynamic therapy is often compromised by the short life time and limited diffusion radius of singlet oxygen as well as uncontrolled intracellular distribution of photosensitizer. It was hypothesized that rapid photosensitizer release upon nanoparticle internalization and its preferred accumulation in mitochondria would address the above problems. Hence, the aim of this study was to engineer a multifunctional micellar nanosystem featured with singlet oxygen-responsive cargo release and mitochondria-targeting. An imidazole-bearing amphiphilic copolymer was employed as the micelle building block to encapsulate triphenylphosphonium-pyropheophorbide a (TPP-PPa) conjugate or PPa. Upon laser irradiation, the singlet oxygen produced by TPP-PPa/PPa oxidized the imidazole moiety to produce hydrophilic urea, leading to micelle disassembly and rapid cargo release. The co-localization analysis showed that the TPP moiety significantly enhanced the photosensitizer uptake by mitochondria, improved mitochondria depolarization upon irradiation, and hence boosted the cytotoxicity in 4T1 cells. The targeting strategy also dramatically reduced the intracellular ATP concentration as a consequence of mitochondria injury. The mitochondria damage was accompanied with the activation of the apoptosis signals (caspase 3 and caspase 9), whose level was directly correlated to the apoptosis extent. The current work provides a facile and robust means to enhance the efficacy of photodynamic therapy.

Pharmaceutical micelles featured with singlet oxygen-responsive cargo release and mitochondrial targeting for enhanced photodynamic therapy

NASA Astrophysics Data System (ADS)

Zhang, Xin; Yan, Qi; Naer Mulatihan, Di; Zhu, Jundong; Fan, Aiping; Wang, Zheng; Zhao, Yanjun

2018-06-01

The efficacy of nanoparticulate photodynamic therapy is often compromised by the short life time and limited diffusion radius of singlet oxygen as well as uncontrolled intracellular distribution of photosensitizer. It was hypothesized that rapid photosensitizer release upon nanoparticle internalization and its preferred accumulation in mitochondria would address the above problems. Hence, the aim of this study was to engineer a multifunctional micellar nanosystem featured with singlet oxygen-responsive cargo release and mitochondria-targeting. An imidazole-bearing amphiphilic copolymer was employed as the micelle building block to encapsulate triphenylphosphonium-pyropheophorbide a (TPP-PPa) conjugate or PPa. Upon laser irradiation, the singlet oxygen produced by TPP-PPa/PPa oxidized the imidazole moiety to produce hydrophilic urea, leading to micelle disassembly and rapid cargo release. The co-localization analysis showed that the TPP moiety significantly enhanced the photosensitizer uptake by mitochondria, improved mitochondria depolarization upon irradiation, and hence boosted the cytotoxicity in 4T1 cells. The targeting strategy also dramatically reduced the intracellular ATP concentration as a consequence of mitochondria injury. The mitochondria damage was accompanied with the activation of the apoptosis signals (caspase 3 and caspase 9), whose level was directly correlated to the apoptosis extent. The current work provides a facile and robust means to enhance the efficacy of photodynamic therapy.

Micro-Encapsulated Porphyrins and Phthalocyanines - New Formulations in Photodynamic Therapy

NASA Astrophysics Data System (ADS)

Ion, R. M.

2017-06-01

Photodynamic therapy (PDT), as an innovative method for cancer tretament is based on a concerted action of some drugs, called sensitizers, which generate reactive oxygen species via a photochemical mechanism, leading to cellular necrosis or apoptosis. The present work aims at loading some sensitizers, as porphyrins (P) and phthalocyanines (Pc) into alginate particles. Particles were prepared by dropping alginate into an aqueous solution containing P or Pc and CaCl2, which allows the formation of particles through ionic crosslinking. It was obtained P or Pc loaded alginate beads with an average diameter of about 100 μm. For these systems, this paper analyses the spectroscopic properties, encapsulation into microcapsules, controlled releasing action and their photosensitizer capacity (singlet oxygen generation).

Atmospheric pressure cold plasma as an antifungal therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Peng; Wu Haiyan; Sun Yi

2011-01-10

A microhollow cathode based, direct-current, atmospheric pressure, He/O{sub 2} (2%) cold plasma microjet was used to inactive antifungal resistants Candida albicans, Candida krusei, and Candida glabrata in air and in water. Effective inactivation (>90%) was achieved in 10 min in air and 1 min in water. Antifungal susceptibility tests showed drastic reduction of the minimum inhibitory concentration after plasma treatment. The inactivation was attributed to the reactive oxygen species generated in plasma or in water. Hydroxyl and singlet molecular oxygen radicals were detected in plasma-water system by electron spin resonance spectroscopy. This approach proposed a promising clinical dermatology therapy.

Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1 O 2 generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wenting; Han, Congcong; Zhang, Qinhua

advanced photosensitizers for singlet oxygen (1O2) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the 1O2 generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (DEST) and hence generate 1O2 effectively. Due to its significant and selectivity for 1O2 generation, the as-prepared carbon nitride-based photosensitizer shows a high selectivemore » photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated PtII complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization.« less

Advanced Singlet Oxygen Generator

DTIC Science & Technology

2009-01-01

bc PP P 1 P PP Ur ) rH (2exp)1U1(1 m )rHx(Q1U ll lb t (18) For the estimation of the O2(1D) yield we will assume that detachment yield Yd is constant......At higher centrifugal acceleration of ~4´ 103m /s2 the gas bubbling was observed and the bubble shape close to the sphere. For large nozzle diameter (~1

Photosensitization of InP/ZnS quantum dots for anti-cancer and anti-microbial applications

NASA Astrophysics Data System (ADS)

Nadeau, Jay; Chibli, Hicham; Carlini, Lina

2012-03-01

Cadmium-free quantum dots (QDs), such as those made from InP, show similar optical properties to those containing toxic heavy metals and thus provide a promising alternative for imaging and therapeutics. The band gap of InP is similar to that of CdTe, so photosensitization of InP QDs with porphyrins or other dyes should lead to generation of reactive oxygen species, useful for targeted destruction of malignant cells or pathogenic bacteria. Here we show the results of measurements of singlet oxygen and superoxide generation from InP QDs with single and double ZnS shells compared with CdTe and CdSe/ZnS. Reactive oxygen species are measured using colorimetric or fluorescent reporter assays and spin-trap electron paramagnetic resonance (EPR) spectroscopy. We find that the size of the InP QDs and the thickness of the ZnS shell both strongly influence ROS generation. These results suggest future approaches to the design of therapeutic nanoparticles.

Direct evidence of charge separation in a metal-organic framework: efficient and selective photocatalytic oxidative coupling of amines via charge and energy transfer.

PubMed

Xu, Caiyun; Liu, Hang; Li, Dandan; Su, Ji-Hu; Jiang, Hai-Long

2018-03-28

The selective aerobic oxidative coupling of amines under mild conditions is an important laboratory and commercial procedure yet a great challenge. In this work, a porphyrinic metal-organic framework, PCN-222, was employed to catalyze the reaction. Upon visible light irradiation, the semiconductor-like behavior of PCN-222 initiates charge separation, evidently generating oxygen-centered active sites in Zr-oxo clusters indicated by enhanced porphyrin π-cation radical signals. The photogenerated electrons and holes further activate oxygen and amines, respectively, to give the corresponding redox products, both of which have been detected for the first time. The porphyrin motifs generate singlet oxygen based on energy transfer to further promote the reaction. As a result, PCN-222 exhibits excellent photocatalytic activity, selectivity and recyclability, far superior to its organic counterpart, for the reaction under ambient conditions via combined energy and charge transfer.

A compact fiber-optic probe-based singlet oxygen luminescence detection system.

PubMed

Gemmell, Nathan R; McCarthy, Aongus; Kim, Michele M; Veilleux, Israel; Zhu, Timothy C; Buller, Gerald S; Wilson, Brian C; Hadfield, Robert H

2017-02-01

This paper presents a novel compact fiberoptic based singlet oxygen near-infrared luminescence probe coupled to an InGaAs/InP single photon avalanche diode (SPAD) detector. Patterned time gating of the single-photon detector is used to limit unwanted dark counts and eliminate the strong photosensitizer luminescence background. Singlet oxygen luminescence detection at 1270 nm is confirmed through spectral filtering and lifetime fitting for Rose Bengal in water, and Photofrin in methanol as model photosensitizers. The overall performance, measured by the signal-to-noise ratio, improves by a factor of 50 over a previous system that used a fiberoptic-coupled superconducting nanowire single-photon detector. The effect of adding light scattering to the photosensitizer is also examined as a first step towards applications in tissue in vivo. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Guest and solvent modulated photo-driven charge separation and triplet generation in a perylene bisimide cyclophane

DOE PAGES

Spenst, Peter; Young, Ryan M.; Wasielewski, Michael R.; ...

2016-05-18

Cofacial positioning of two perylene bisimide (PBI) chromophores at a distance of 6.5 Å in a cyclophane structure prohibits the otherwise common excimer formation and directs photoexcited singlet state relaxation towards intramolecular symmetry-breaking charge separation (τ CS = 161 ± 4 ps) in polar CH 2Cl 2, which is thermodynamically favored with a Gibbs free energy of ΔG CS = –0.32 eV. The charges then recombine slowly in τ CR = 8.90 ± 0.06 ns to form the PBI triplet excited state, which can be used subsequently to generate singlet oxygen in 27% quantum yield. This sequence of events ismore » eliminated by dissolving the PBI cyclophane in non-polar toluene, where only excited singlet state decay occurs. In contrast, complexation of electron-rich aromatic hydrocarbons by the host PBI cyclophane followed by photoexcitation of PBI results in ultrafast electron transfer (<10 ps) from the guest to the PBI in CH 2Cl 2. As a result, the rate constants for charge separation and recombination increase as the guest molecules become easier to oxidize, demonstrating that charge separation occurs close to the peak of the Marcus curve and the recombination lies far into the Marcus inverted region.« less

The role of microbial low-molecular-weight autoregulatory factors (alkylhydroxybenzenes) in resistance of microorganisms to radiation

NASA Astrophysics Data System (ADS)

El-Registan, G. I.; Mulyukin, A. L.; Nikolaev, Yu. A.; Stepanenko, I. Yu.; Shanenko, E. A.; Strakhovskaya, M. G.; Revina, A. A.

Low-molecular-weight cell-to-cell communication factors are produced by various pro- and eukaryotes and involved in autoregulation of the growth and development of microbial cultures. As for some bacterial and yeast species, these factors were identified as isomers and homologs of alkylhydroxybenzenes (AHBs). Depending on the concentration, they participate in controlling the transition to stationary phase, entering the resting state, and stress resistance of vegetative cells to gamma-irradiation, photooxidation (singlet oxygen), heat shock. Chemical analogs of microbial AHBs protected microbial cultures from stressful situations and prolonged starvation and exerted (1) the stabilizing activity toward biomacromolecules and supermolecular structures (cell membranes) and (2) the ability to scavenge active oxygen species. The stabilizing effect of AHBs as chemical chaperones resulted from their complex formation with protected macromolecules due to intermolecular hydrogen bonds, hydrophobic and electrostatic interactions and was demonstrated on models of individual enzymes (trypsin, amylase, etc.). The action of AHBs as active oxygen species scavengers was related to their oxidative conversion to water-insoluble polymeric products. Particularly, AHBs protected the yeast from the action of (a) active oxygen species formed during gamma-irradiation (50 krad, 196 rad/sec) or (b) singlet oxygen generated in cells photosensitized by chlorin e6 (10 mkg/L). It is important that microbial AHBs were not species-specific and defended cultured animal cells (ras-transformed fibroblasts) from the action of organic toxicants. The use of AHBs as protectants and adaptogens will be discussed as well as perspectives of further investigations.

The role of microbial low-molecular-weight autoregulatory factors (alkylhydroxybenzenes) in resistance of microorganisms to radiation and heat shock

NASA Astrophysics Data System (ADS)

El-Registan, Galina I.; Mulyukin, Andrey L.; Nikolaev, Yuri A.; Stepanenko, Irina Yu.; Kozlova, Alla N.; Martirosova, Elena I.; Shanenko, Elena F.; Strakhovskaya, Marina G.; Revina, Aleksandra A.

Low-molecular-weight cell-to-cell communication factors are produced by various pro- and eukaryotes and involved in autoregulation of the growth and development of microbial cultures. As for some bacterial and yeast species, these factors were identified as isomers and homologues of alkylhydroxybenzenes (AHB). Depending on the concentration, they participate in controlling the transition to stationary phase, entering the resting state, and stress resistance of vegetative cells to gamma-irradiation, photooxidation (singlet oxygen), and heat shock. Chemical analogues of microbial AHB protected microbial cultures from stressful situations and exerted (1) the stabilizing activity toward macromolecules and (2) the ability to scavenge active oxygen species. The stabilizing effect of AHBs resulted from their complex formation with protected macromolecules due to intermolecular hydrogen bonds, hydrophobic and electrostatic interactions and was demonstrated on models of individual enzymes (trypsin). Particularly, AHBs protected the yeast from the action of (a) active oxygen species formed during gamma-irradiation (500 Gy, 1.96 Gy/s) or (b) singlet oxygen generated in cells photosensitized by chlorin e 6 (10 μg/L). It is important that microbial AHBs were not species-specific and defended cultured microbial and animal cells from the action of organic toxicants. The use of AHBs as protectants and adaptogens is discussed as well as perspectives of further investigations.

Excited singlet molecular O2 (1Δg) is generated enzymatically from excited carbonyls in the dark

PubMed Central

Mano, Camila M.; Prado, Fernanda M.; Massari, Júlio; Ronsein, Graziella E.; Martinez, Glaucia R.; Miyamoto, Sayuri; Cadet, Jean; Sies, Helmut; Medeiros, Marisa H. G.; Bechara, Etelvino J. H.; Di Mascio, Paolo

2014-01-01

In mammalian tissues, ultraweak chemiluminescence arising from biomolecule oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [O2 (1Δg)] and electronically excited triplet carbonyl products involving dioxetane intermediates. Herein, we describe evidence of the generation of O2 (1Δg) in aqueous solution via energy transfer from excited triplet acetone. This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source. Both sources of excited carbonyls showed characteristic light emission at 1,270 nm, directly indicative of the monomolecular decay of O2 (1Δg). Indirect analysis of O2 (1Δg) by electron paramagnetic resonance using the chemical trap 2,2,6,6-tetramethylpiperidine showed the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl. Using [18O]-labeled triplet, ground state molecular oxygen [18O2 (3Σg-)], chemical trapping of 18O2 (1Δg) with disodium salt of anthracene-9,10-diyldiethane-2,1-diyl disulfate yielding the corresponding double-[18O]-labeled 9,10-endoperoxide, was detected through mass spectrometry. This corroborates formation of O2 (1Δg). Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates 18O2 (1Δg) by triplet-triplet energy transfer to ground state oxygen O2 (3Σg−), and supports the long formulated hypothesis of O2 (1Δg) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light. PMID:25087485

Hypericin-loaded lipid nanocapsules for photodynamic cancer therapy in vitro

NASA Astrophysics Data System (ADS)

Barras, Alexandre; Boussekey, Luc; Courtade, Emmanuel; Boukherroub, Rabah

2013-10-01

Hypericin (Hy), a naturally occurring photosensitizer (PS), is extracted from Hypericum perforatum plants, commonly known as St. John's wort. The discovery of the in vitro and in vivo photodynamic activities of hypericin as a photosensitizer generated great interest, mainly to induce a very potent antitumoral effect. However, this compound belongs to the family of naphthodianthrones which are known to be poorly soluble in physiological solutions and produce non-fluorescent aggregates (A. Wirz et al., Pharmazie, 2002, 57, 543; A. Kubin et al., Pharmazie, 2008, 63, 263). These phenomena can reduce its efficiency as a photosensitizer for the clinical application. In the present contribution, we have prepared, characterized, and studied the photochemical properties of Hy-loaded lipid nanocapsule (LNC) formulations. The amount of singlet oxygen (1O2) generated was measured by the use of p-nitroso-dimethylaniline (RNO) as a selective scavenger under visible light irradiation. Our results showed that Hy-loaded LNCs suppressed aggregation of Hy in aqueous media, increased its apparent solubility, and enhanced the production of singlet oxygen in comparison with free drug. Indeed, encapsulation of Hy in LNCs led to an increase of 1O2 quantum yield to 0.29-0.44, as compared to 0.02 reported for free Hy in water. Additionally, we studied the photodynamic activity of Hy-loaded LNCs on human cervical carcinoma (HeLa) and Human Embryonic Kidney (HEK) cells. The cell viability decreased radically to 10-20% at 1 μM, reflecting Hy-loaded LNC25 phototoxicity.Hypericin (Hy), a naturally occurring photosensitizer (PS), is extracted from Hypericum perforatum plants, commonly known as St. John's wort. The discovery of the in vitro and in vivo photodynamic activities of hypericin as a photosensitizer generated great interest, mainly to induce a very potent antitumoral effect. However, this compound belongs to the family of naphthodianthrones which are known to be poorly soluble in physiological solutions and produce non-fluorescent aggregates (A. Wirz et al., Pharmazie, 2002, 57, 543; A. Kubin et al., Pharmazie, 2008, 63, 263). These phenomena can reduce its efficiency as a photosensitizer for the clinical application. In the present contribution, we have prepared, characterized, and studied the photochemical properties of Hy-loaded lipid nanocapsule (LNC) formulations. The amount of singlet oxygen (1O2) generated was measured by the use of p-nitroso-dimethylaniline (RNO) as a selective scavenger under visible light irradiation. Our results showed that Hy-loaded LNCs suppressed aggregation of Hy in aqueous media, increased its apparent solubility, and enhanced the production of singlet oxygen in comparison with free drug. Indeed, encapsulation of Hy in LNCs led to an increase of 1O2 quantum yield to 0.29-0.44, as compared to 0.02 reported for free Hy in water. Additionally, we studied the photodynamic activity of Hy-loaded LNCs on human cervical carcinoma (HeLa) and Human Embryonic Kidney (HEK) cells. The cell viability decreased radically to 10-20% at 1 μM, reflecting Hy-loaded LNC25 phototoxicity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02724d

Cyclodextrin-gated mesoporous silica nanoparticles as drug carriers for red light-induced drug release

NASA Astrophysics Data System (ADS)

Chai, Shiqiang; Guo, Yu; Zhang, Zhenyu; Chai, Zhen; Ma, Yurong; Qi, Limin

2017-04-01

Long wavelength light-responsive drug delivery systems based on mesoporous silica nanoparticles (MSNs) have attracted much attention in the last few years. In this paper, a red light (660 nm)-responsive drug delivery system based on low-cost cyclodextrin (CD)-gated MSNs containing a photodynamic therapy (PDT) photosensitizer (Chlorin e6, Ce6) was developed for the first time. The drug release experiment in water demonstrated that with the irradiation of red light, Ce6 can be excited to generate singlet oxygen, which can further cleave the singlet oxygen sensitive linker to trigger the departure of CD and the release of cargo. Further in vitro release experiments confirmed that cargo can be released from MSNs with the irradiation of red light and spread into the entire cell. The relative low power density (0.5 W cm-2) of excitation light together with the short irradiation time (one-three min) result in a low light dose (30-90 J cm-2) for the drug delivery, contributing to their potential clinical applications.

Mechanism of virus inactivation by cold atmospheric-pressure plasma and plasma-activated water.

PubMed

Guo, Li; Xu, Ruobing; Gou, Lu; Liu, Zhichao; Zhao, Yiming; Liu, Dingxin; Zhang, Lei; Chen, Hailan; Kong, Michael G

2018-06-18

Viruses are serious pathogenic contamination that severely affect the environment and human health. Cold atmospheric-pressure plasma efficiently inactivates pathogenic bacteria, however, the mechanism of virus inactivation by plasma is not fully understood. In this study, surface plasma in argon mixed with 1% air and plasma-activated water were used to treat water containing bacteriophages. Both agents efficiently inactivated bacteriophages T4, Φ174, and MS2 in a time-dependent manner. Prolonged storage had marginal effects on the anti-viral activity of plasma-activated water. DNA and protein analysis revealed that the reactive species generated by plasma damaged both nucleic acid and proteins, in consistent with the morphological examination showing that plasma treatment caused the aggregation of bacteriophages. The inactivation of bacteriophages was alleviated by the singlet oxygen scavengers, demonstrating that singlet oxygen played a primary role in this process. Our findings provide a potentially effective disinfecting strategy to combat the environmental viruses using cold atmospheric-pressure plasma and plasma-activated water. Importance Contamination with pathogenic and infectious viruses severely threaten human health and animal husbandry. Current methods for disinfection have different disadvantages, such as inconvenience and contamination of disinfection by-products (e.g. chlorine disinfection). In this study, atmospheric surface plasma in argon mixed with air and plasma-activated water were found to efficiently inactivate bacteriophages, and plasma-activated water still had strong anti-viral activity after prolonged storage. Furthermore, it was shown that bacteriophage inactivation was associated with the damage to nucleic acid and proteins by singlet oxygen. The understanding of the biological effects of plasma-based treatment is useful to inform the development of plasma into a novel disinfecting strategy with convenience and no by-product. Copyright © 2018 Guo et al.

Identifying the Nonradical Mechanism in the Peroxymonosulfate Activation Process: Singlet Oxygenation Versus Mediated Electron Transfer.

PubMed

Yun, Eun-Tae; Lee, Jeong Hoon; Kim, Jaesung; Park, Hee-Deung; Lee, Jaesang

2018-06-01

Select persulfate activation processes were demonstrated to initiate oxidation not reliant on sulfate radicals, although the underlying mechanism has yet to be identified. This study explored singlet oxygenation and mediated electron transfer as plausible nonradical mechanisms for organic degradation by carbon nanotube (CNT)-activated peroxymonosulfate (PMS). The degradation of furfuryl alcohol (FFA) as a singlet oxygen ( 1 O 2 ) indicator and the kinetic retardation of FFA oxidation in the presence of l-histidine and azide as 1 O 2 quenchers apparently supported a role of 1 O 2 in the CNT/PMS system. However, the 1 O 2 scavenging effect was ascribed to a rapid PMS depletion by l-histidine and azide. A comparison of CNT/PMS and photoexcited Rose Bengal (RB) excluded the possibility of singlet oxygenation during heterogeneous persulfate activation. In contrast to the case of excited RB, solvent exchange (H 2 O to D 2 O) did not enhance FFA degradation by CNT/PMS and the pH- and substrate-dependent reactivity of CNT/PMS did not reflect the selective nature of 1 O 2 . Alternatively, concomitant PMS reduction and trichlorophenol oxidation were achieved when PMS and trichlorophenol were physically separated in two chambers using a conductive vertically aligned CNT membrane. This result suggested that CNT-mediated electron transfer from organics to persulfate was primarily responsible for the nonradical degradative route.

Inactivation of virus in solution by cold atmospheric pressure plasma: identification of chemical inactivation pathways

NASA Astrophysics Data System (ADS)

Aboubakr, Hamada A.; Gangal, Urvashi; Youssef, Mohammed M.; Goyal, Sagar M.; Bruggeman, Peter J.

2016-05-01

Cold atmospheric pressure plasma (CAP) inactivates bacteria and virus through in situ production of reactive oxygen and nitrogen species (RONS). While the bactericidal and virucidal efficiency of plasmas is well established, there is limited knowledge about the chemistry leading to the pathogen inactivation. This article describes a chemical analysis of the CAP reactive chemistry involved in the inactivation of feline calicivirus. We used a remote radio frequency CAP produced in varying gas mixtures leading to different plasma-induced chemistries. A study of the effects of selected scavengers complemented with positive control measurements of relevant RONS reveal two distinctive pathways based on singlet oxygen and peroxynitrous acid. The first mechanism is favored in the presence of oxygen and the second in the presence of air when a significant pH reduction is induced in the solution by the plasma. Additionally, smaller effects of the H2O2, O3 and \\text{NO}2- produced were also found. Identification of singlet oxygen-mediated 2-imidazolone/2-oxo-His (His  +14 Da)—an oxidative modification of His 262 comprising the capsid protein of feline calicivirus links the plasma induced singlet oxygen chemistry to viral inactivation.

Synthesis and in vitro phototoxicity of multifunctional Zn(II)meso-tetrakis(4-carboxyphenyl)porphyrin-coated gold nanoparticles assembled via axial coordination with imidazole ligands.

PubMed

Alea-Reyes, María E; Penon, Oriol; García Calavia, Paula; Marín, María J; Russell, David A; Pérez-García, Lluïsa

2018-07-01

Metalloporphyrins are extensively investigated for their ability to form reactive oxygen species and as potent photosensitisers for use in photodynamic therapy. However, their hydrophobicity generally causes solubility issues concerning in vivo delivery due to lack of distribution and low clearance from the body. Immobilising porphyrins on carriers, such as gold nanoparticles (GNP), can overcome some of these drawbacks. The mode of assembling the porphyrins to the carrier influences the properties of the resulting drug delivery systems. We describe the synthesis and characterisation of new porphyrin decorated water soluble GNP and we explore Zn-imidazole axial coordination as the mode of linking the porphyrin to the metallic core of the nanoparticles. Quantification of singlet oxygen production, toxicity in dark, cellular uptake by SK-BR-3 cells and phototoxicity have been assessed. Axial coordination limits the number of porphyrins on the gold surface, reduces the formation of aggregates, and diminishes metal exchange in the porphyrin, all of which contribute to enhance the efficiency of singlet oxygen generation from the immobilised porphyrin. In vitro experiments on SK-BR-3 cells reveal a fast uptake followed by more than 80% cell death after irradiation with low doses of light. Copyright © 2018 Elsevier Inc. All rights reserved.

In vitro phototoxic potential and photochemical properties of imidazopyridine derivative: a novel 5-HT4 partial agonist.

PubMed

Onoue, Satomi; Igarashi, Naoko; Yamauchi, Yukinori; Kojima, Takashi; Murase, Noriaki; Zhou, Yu; Yamada, Shizuo; Tsuda, Yoshiko

2008-10-01

Drug-induced phototoxic skin responses have been recognized as undesirable side effects, and as we previously proposed the determination of reactive oxygen species (ROS) from photo-irradiated compounds can be effective for the prediction of phototoxic potential. In this investigation, we evaluated the photosensitizing properties of imidazopyridine derivative, a novel 5-HT(4) partial agonist, using ROS assay and several analytical/biochemical techniques. Exposure of the compound to simulated sunlight resulted in the significant production of singlet oxygen, which is indicative of its phototoxic potential. In practice, an imidazopyridine derivative under UVA/B light exposure also showed significant photodegradation and even photobiochemical events; peroxidation of fatty acid and genetic damage after DNA-binding, which are considered as causative agents for phototoxic dermatitis. Interestingly, both photodegradation and lipoperoxidation were dramatically attenuated by the addition of radical scavengers, especially singlet oxygen quenchers, suggesting the possible involvement of ROS generation in the phototoxic pathways. In the 3T3 neutral red uptake phototoxicity test, imidazopyridine derivative also showed the phototoxic effect on 3T3 mouse fibroblast cells. These results suggest the phototoxic risk of newly synthesized imidazopyridine derivative and also verify the usefulness of ROS assay for phototoxicity prediction. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

Enhanced red emission of 808 nm excited upconversion nanoparticles by optimizing the composition of shell for efficient generation of singlet oxygen

NASA Astrophysics Data System (ADS)

Liu, Jinxue; Zhang, Tingbin; Song, Xiaoyan; Xing, Jinfeng

2018-01-01

With the aim to enhance the upconversion luminescence (UCL) intensity, much attention was paid to reduce the energy-back transfer from Er3+ ions to Nd3+ ions by constructing various kinds of multilayer upconversion nanoparticles (UCNPs). However, the energy-back transfer was difficult to be completely eliminated. Also, the thick shell of multilayer UCNPs is not favourable for effective Förster resonance energy transfer (FRET) in photodynamic therapy (PDT) system. Herein, an effective and facile method was applied to prepare UCNPs by optimizing the composition to largely enhance the red emission (at 660 nm) for efficient generation of singlet oxygen (1O2). In detail, the concentrations of Nd3+ ions and Yb3+ ions doped in the sensitizing shell were systematically researched to balance the energy back-transfer and the light harvest ability. The optimal emission and a relatively high Red/Green (R/G) ratio of NaYF4:Yb,Er,Nd@NaYF4:Yb0.1Nd0.2 UCNPs were obtained simultaneously. Furthermore, the emission under 980 nm excitation demonstrated the energy back-transfer from Er3+ to Yb3+ ions was also notable which was largely ignored previously. Then, UCNPs were encapsulated into mesoporous silica shell, and the photosensitizer Chlorin e6 (Ce6) was covalently conjugated to form a non-leaking nanoplatform. The efficiency of 1O2 generation obviously increased with the enhanced emission of UCNPs.

Mechanism of isomers and analogues of resveratrol dimers selectively quenching singlet oxygen by UHPLC-ESI-MS2.

PubMed

Yin, Xuefeng; Yu, Jia; Kong, Qingjun; Ren, Xueyan

2017-12-15

Stilbenoids, in particular, resveratrol and its dimers are abundantly present in Vitis vinifera and proved to be quenchers with selective singlet oxygen. However, only a few mechanisms are reported for their complex molecular architectures. Hence, UHPLC combined with accurate MS is employed to investigate the photo-radiation mechanism of resveratrol dimers systematically. Ⅰ: Resorcinol ring exists in Scirpusin A 1, Trans-ε-viniferin 2 and Trans-σ-viniferin 3. The photochemical products were 14Da or 16Da higher than reagents and underwent an endoperoxide intermediate to quinones; Ⅱ: [2+2] cyclization of intra-molecular trans-double bond. The products were 18Da greater than substrates thereby cycloaddited to oxygen heterocyclic; Ⅲ : [4+1], [4+2] cyclization of oxetane formed products were 28Da and 44Da higher than 3, 2 and 1. Ⅳ : 5-phenol-2,3-dihydrobenzofuran ring exists in 2 been oxidized, causing the products at 16Da, 32Da higher than 2. This is the first to reveal the generally regular mechanism of stilbenoids quenching singlet oxygen. Copyright © 2017 Elsevier Ltd. All rights reserved.

Immobilization of zinc phthalocyanines in silicate matrices and investigation of their photobactericidal effect on E. coli.

PubMed

Artarsky, Spas; Dimitrova, Stanislava; Bonnett, Raymond; Krysteva, Milka

2006-03-26

The aim of the present investigation was to immobilize zinc phthalocyanines in a silicate matrix and to test the photobactericidal properties of the matrices so prepared toward Esherichia coli in model aqueous media. For the purpose, tetra tertiary butyl zinc phthalocyanine (TBZnPc) and zinc phthalocyanine tetrasulfonic acid (ZnPcTS) were used. The abilities of these two photosensitizers to generate singlet oxygen in solution were compared by following the rate of photobleaching of 1,3-diphenylisobenzofuran (DPBF) at 430 nm in dimethylformamide (DMF). The results of this study show clearly that, under the conditions used here, the TBZnPc is the more effective generator of singlet oxygen; with it the DPBF was virtually completely photobleached in 4 min, while with the ZnPcTS under the same conditions, it took 12 min to reach this point. Glass conjugates with the two phthalocyanines were obtained by the sol-gel technique and were characterized by a well-defined color due to the phthalocyanine incorporated in the silicate matrix. Glasses with an intense, but inhomogeneous, green color were obtained when the tetrasulfonic derivative of the zinc phthalocyanine was used, while blue glasses of evenly distributed coloration were formed from the tetra tertiary butyl derivative. The ZnPcTS conjugate demonstrates more effective singlet oxygen evolution than is the case with the TBZnPc conjugate. These results are the opposite of those obtained for the free phthalocyanines in solution. The structural formulae of the compounds show that TBZnPc has a more pronounced hydrophobic character than the sulfonic derivative. In our view, the relative reactivities of the conjugates can be explained by the tetrasulfonic derivative being situated mainly in the surface parts of the glass matrix where the hydrophilic character is prevailing, while the tertiary butyl derivative is mainly present in the internal parts of the matrix as a result of which it is less accessible and therefore less active. The results obtained on the effect of zinc phthalocyanine conjugates on E. coli show a trend similar to that observed with singlet oxygen evolution shown. Thus, for the ZnPcTS conjugate, the log kill is 1.32 and for the TBZnPc conjugate, it is 0.98, in each case after 120 min. The results obtained show that phthalocyanines can be immobilized successfully in a silicate matrix and used for photodisinfection of microbially polluted waters. The silicate matrix has some advantages in comparison with other organic matrices. It is insoluble in water, resistant towards microorganisms, easy to fabricate, and might be developed successfully for the photodisinfection of water, e.g., in swimming pools and in other open water reservoirs.

Optogenetic mutagenesis in Caenorhabditis elegans.

PubMed

Noma, Kentaro; Jin, Yishi

2015-12-03

Reactive oxygen species (ROS) can modify and damage DNA. Here we report an optogenetic mutagenesis approach that is free of toxic chemicals and easy to perform by taking advantage of a genetically encoded ROS generator. This method relies on the potency of ROS generation by His-mSOG, the mini singlet oxygen generator, miniSOG, fused to a histone. Caenorhabditis elegans expressing His-mSOG in the germline behave and reproduce normally, without photoinduction. Following exposure to blue light, the His-mSOG animals produce progeny with a wide range of heritable phenotypes. We show that optogenetic mutagenesis by His-mSOG induces a broad spectrum of mutations including single-nucleotide variants (SNVs), chromosomal deletions, as well as integration of extrachromosomal transgenes, which complements those derived from traditional chemical or radiation mutagenesis. The optogenetic mutagenesis expands the toolbox for forward genetic screening and also provides direct evidence that nuclear ROS can induce heritable and specific genetic mutations.

Optogenetic mutagenesis in Caenorhabditis elegans

PubMed Central

Noma, Kentaro; Jin, Yishi

2015-01-01

Reactive oxygen species (ROS) can modify and damage DNA. Here we report an optogenetic mutagenesis approach that is free of toxic chemicals and easy to perform by taking advantage of a genetically encoded ROS generator. This method relies on the potency of ROS generation by His-mSOG, the mini singlet oxygen generator, miniSOG, fused to a histone. Caenorhabditis elegans expressing His-mSOG in the germline behave and reproduce normally, without photoinduction. Following exposure to blue light, the His-mSOG animals produce progeny with a wide range of heritable phenotypes. We show that optogenetic mutagenesis by His-mSOG induces a broad spectrum of mutations including single-nucleotide variants (SNVs), chromosomal deletions, as well as integration of extrachromosomal transgenes, which complements those derived from traditional chemical or radiation mutagenesis. The optogenetic mutagenesis expands the toolbox for forward genetic screening and also provides direct evidence that nuclear ROS can induce heritable and specific genetic mutations. PMID:26632265

Singlet oxygenation of 1,2-poly/1,4-hexadiene/s

NASA Technical Reports Server (NTRS)

Golub, M. A.; Rosenberg, M. L.; Gemmer, R. V.

1979-01-01

The microstructural changes that occur in cis and trans forms of 1,2-poly(1,4-hexadiene) during methylene blue-photosensitized oxidation were examined by infrared and (C-13)-NMR spectroscopy. The singlet oxygenation of these polymers yielded the expected allylic hydroperoxides accompanied by double bond shifts to new vinyl and trans-vinylene double bonds. The photosensitized oxidation exhibited zero-order kinetics; the relative rates for the cis- and trans-1,2-poly(1,4-hexadiene)s were approximately 3.8:1.0.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koch, T.H.

Coumarin laser dyes upon excitation degrade to produce products that absorb at the lasing wavelength. This results in attenuation of dye laser output through interference of stimulated emission. The roles of singlet oxygen and excitation intensity on dye degradation were explored. Singlet oxygen is formed but its reactions with the dye do not appear to be a major cause of dye laser output deterioration. High light intensity results in dye-sensitized, solvent oligomerization to yield materials that interfere with dye-stimulated emission. 1, 4-Diazabicyclo2,2,2octane (DABCO)inhibits this oligomerization.

A multifunctional nanoassembly of mesogen-bearing amphiphiles and porphyrins for the simultaneous photodelivery of nitric oxide and singlet oxygen.

PubMed

Caruso, Elisa B; Cicciarella, Enzo; Sortino, Salvatore

2007-12-21

We report a molecular nanoassembly able to supply simultaneously, in the same region of space and under the exclusive control of visible light, nitric oxide and singlet oxygen, two species playing a key role in the therapy of cancer; the considerable fluorescence of this nanoaggregate and its reduced size (ca. 40 nm) represent additional advantages that make this photoactive vehicle an appealing candidate to be tested in biological systems.

Long-term luminescence of sensibilizers in tissues at the conditions of oxygen deficiency due to photodynamic effect

NASA Astrophysics Data System (ADS)

Ishemgulov, A. T.; Letuta, S. N.; Pashkevich, S. N.; Alidzhanov, E. K.; Lantukh, Yu. D.

2017-11-01

Long-term luminescence of organic dyes (xanthene dyes, halogen substituted fluoroscein) was used for an in vitro study of the photodynamic effect of exogenic probes in malignant tumors and healthy tissues of mice. It is shown that the photodynamic activity of oxygen and the dynamics of its concentration in tissues can be estimated from the delayed fluorescence of exogenic probes caused by singlet-triplet annihilation of singlet oxygen and excited triplet states of the molecules of photosensitizer dyes. It is found that quenching of long-term luminescence of photosensitizers significantly differs in tumors and normal tissues.

Singlet Molecular Oxygen Generation by Light-Activated DHN-Melanin of the Fungal Pathogen Mycosphaerella fijiensis in Black Sigatoka Disease of Bananas

PubMed Central

Beltrán-García, Miguel J.; Prado, Fernanda M.; Oliveira, Marilene S.; Ortiz-Mendoza, David; Scalfo, Alexsandra C.; Pessoa, Adalberto; Medeiros, Marisa H. G.; White, James F.; Di Mascio, Paolo

2014-01-01

In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis. PMID:24646830

Detection of Singlet Oxygen Formation inside Photoactive Biohybrid Composite Material.

PubMed

Hajdu, Kata; Ur Rehman, Ateeq; Vass, Imre; Nagy, László

2017-12-26

Photosynthetic reaction center proteins (RCs) are the most efficient light energy converter systems in nature. The first steps of the primary charge separation in photosynthesis take place in these proteins. Due to their unique properties, combining RCs with nano-structures promising applications can be predicted in optoelectronic systems. In the present work RCs purified from Rhodobacter sphaeroides purple bacteria were immobilized on multiwalled carbon nanotubes (CNTs). Carboxyl-and amine-functionalised CNTs were used, so different binding procedures, physical sorption and chemical sorption as well, could be applied as immobilization techniques. Light-induced singlet oxygen production was measured in the prepared photoactive biocomposites in water-based suspension by histidine mediated chemical trapping. Carbon nanotubes were applied under different conditions in order to understand their role in the equilibration of singlet oxygen concentration in the suspension. CNTs acted as effective quenchers of ¹O₂ either by physical (resonance) energy transfer or by chemical (oxidation) reaction and their efficiency showed dependence on the diffusion distance of ¹O₂.

Cancer cell death processes in combining photothermal and photodynamic effects through surface plasmon resonance of gold nanoring (Conference Presentation)

NASA Astrophysics Data System (ADS)

He, Yulu; Yu, Jian-He; Hsiao, Jen-Hung; Tu, Yi-Chou; Low, Meng Chun; Hua, Wei-Hsiang; Hsieh, Cheng-Che; Kiang, Yean-Woei; Yang, Chih-Chung; Zhang, Zhenxi

2017-02-01

In combining the photothermal and photodynamic effects for killing cancer cells through the localized surface plasmon resonance (LSP) of photosensitizer-linked Au nanorings (NRIs), which are up-taken by the cells, the cells can be killed via different processes, including necrosis and apoptosis. In particular, the dominating effect, either photothermal or photodynamic effect, for cancer cell killing leading to either necrosis or apoptosis process is an important issue to be understood for improving the therapy efficiency. In this paper, we demonstrate the study results in differentiating the necrosis and apoptosis processes of cell death under different laser illumination conditions. With the LSP resonance wavelength of the Au NRIs around 1064 nm, the illumination of a 1064-nm cw laser can mainly produce the photothermal effect. The illumination of a 1064-nm fs laser can lead to LSP resonance-assisted two-photon absorption of the photosensitizer (AlPcS) for generating singlet oxygen and hence the photodynamic effect, besides the photothermal effect. Also, the illumination of a 660-nm cw laser can result in single-photon absorption of the photosensitizer for generating singlet oxygen and the photodynamic effect. By comparing the necrosis and apoptosis distributions in dead cells between the cases of different laser illumination conditions, we can differentiate the cancer cell killing processes between the photothermal effect, photodynamic effect, and the mixed effect.

Identification of singlet oxygen photosensitizes in lambs drinking water in an alveld risk area in West Norway.

PubMed

Tønnesen, Hanne Hjorth; Mysterud, Ivar; Karlsen, Jan; Skulberg, Olav M; Laane, Carl M M; Schumacher, Trond

2013-02-05

Alveld is a hepatogenous photosensitivity disorder in lambs. Although alveld has been known in Norway for more than 100years, there are still questions related to the cause of the disease. Phytoporphyrin has long been incriminated as the photosensitizer in hepatogenous photosensitivity diseases but previous findings suggest that the photosensitizing mechanism in alveld is more complex, possibly involving other co-factors. The current work investigates the presence of non-hepatogenous photosensitizers originating in lamb's drinking water from various sources. In addition samples of two of the predominent cyanobacteria found in a representative biofilm (i.e. aggregates of microbes) were identified and isolated in axenic (i.e. pure) cultures. Information from the absorption-, fluorescence emission-, and -excitation spectra and the action spectrum for the formation of singlet oxygen was combined in order to identify the chromophores responsible for the formation of singlet oxygen, e.g. phycocyanins from the cyanobacteria. The highest level of singlet oxygen formation was detected in lotic (i.e. flowing) water in the period consistent with the outbreak of the alveld disease in the area. Meteorological data indicate a warm and wet May with a high radiation exposure leading up to a colder and wet June with an even higher solar irradiance. The seasonal variation in the amount of photosensitizers in lamb's drinking water combined meteorological data can be important to predict the outbreak of alveld. Copyright © 2012 Elsevier B.V. All rights reserved.

Fluorescent proteins as singlet oxygen photosensitizers: mechanistic studies in photodynamic inactivation of bacteria

NASA Astrophysics Data System (ADS)

Ruiz-González, Rubén.; White, John H.; Cortajarena, Aitziber L.; Agut, Montserrat; Nonell, Santi; Flors, Cristina

2013-02-01

Antimicrobial photodynamic therapy (aPDT) combines a photosensitizer, light and oxygen to produce reactive oxygen species (ROS), mainly singlet oxygen (1O2), to photo-oxidize important biomolecules and induce cell death. aPDT is a promising alternative to standard antimicrobial strategies, but its mechanisms of action are not well understood. One of the reasons for that is the lack of control of the photosensitizing drugs location. Here we report the use of geneticallyencoded fluorescent proteins that are also 1O2 photosensitizers to address the latter issue. First, we have chosen the red fluorescent protein TagRFP as a photosensitizer, which unlike other fluorescent proteins such as KillerRed, is able to produce 1O2 but not other ROS. TagRFP photosensitizes 1O2 with a small, but not negligible, quantum yield. In addition, we have used miniSOG, a more efficient 1O2 photosensitizing fluorescent flavoprotein that has been recently engineered from phototropin 2. We have genetically incorporated these two photosensitizers into the cytosol of E. coli and demonstrated that intracellular 1O2 is sufficient to kill bacteria. Additional assays have provided further insight into the mechanism of cell death. Photodamage seems to occur primarily in the inner membrane, and extends to the outer membrane if the photosensitizer's efficiency is high enough. These observations are markedly different to those reported for external photosensitizers, suggesting that the site where 1O2 is primarily generated proves crucial for inflicting different types of cell damage.

Oxidation-extraction spectrometry of reactive oxygen species (ROS) generated by chlorophyllin magnesium (Chl-Mg) under ultrasonic irradiation

NASA Astrophysics Data System (ADS)

Guo, Yuwei; Cheng, Chunping; Wang, Jun; Jin, Xudong; Liu, Bin; Wang, Zhiqiu; Gao, Jingqun; Kang, Pingli

2011-09-01

In order to examine the mechanism and process of sonodynamic reaction, the chlorophyllin magnesium (Chl-Mg) acting as a sonosensitizer was irradiated by ultrasound, and the generation of reactive oxygen species (ROS) were detected by the method of oxidation-extraction spectrometry (OES). That is, under ultrasonic irradiation in the presence of Chl-Mg, the 1,5-diphenyl carbazide (DPCI) is oxidized by generated ROS into 1,5-diphenyl carbazone (DPCO), which can be extracted by mixed organic solvent and display a obvious visible absorption at 563 nm wavelength. Besides, the generation conditions of ROS were also reviewed. The results demonstrated that the quantities of generated ROS increased with the increase of ultrasonic irradiation time, Chl-Mg concentration and DPCI concentration. Finally, several radical scavengers (l-Histidine (His), 2,6-Di-tert-butyl-methylphenol (BHT) and Vitamin C (VC)) were used to determine the kind of the generated ROS. It was found that at least the hydroxyl radical (OH) and singlet oxygen ( 1O 2) were generated in the presence of Chl-Mg under ultrasonic irradiation. It is wish that this paper might offer some valuable references for the study on the mechanism of SDT and the application of Chl-Mg in tumor treatment.

Production and Consumption of Reactive Oxygen Species by Fullerenes

EPA Science Inventory

Reactive oxygen species (ROS) are one of the most important intermediates in chemical, photochemical, and biological processes. To understand the environmental exposure and toxicity of fullerenes better, the production and consumption of ROS (singlet oxygen, superoxide, hydrogen ...

Quantum-Chemical Simulation of the Solvent Effect on Spontaneous Emission of Singlet Oxygen

NASA Astrophysics Data System (ADS)

Ivashin, N. V.; Shchupak, E. E.

2018-01-01

A molecular simulation of the solvent effect on radiative rate constant k r of singlet oxygen is carried out. This study included a search for the most probable conformations of the complexes of molecules of singlet oxygen and ten solvents and calculation of dipole moments M of transitions a 1Δ g -b1Σ g + ( M a-b ) and a 1Δ g - X 3Σ g - ( M a-X ) of the oxygen molecule for them. Averaging of M a-b by conformations, taking into account the probability of their formation for complexes without atoms with a large atomic number (Cl, S), yields values that, as a rule, correlate well with the behavior of k r in the experiment. Taking into account the possibility of decreasing the distance (compared to equilibrium) between molecules in a collision complex at room temperature made it possible to achieve satisfactory agreement of the calculated and experimental data also for complexes with CCl4, C2Cl4, and CS2. The obtained data indicate that a number of factors affect k r . The correlation of k r with molecular polarizability in a number of cases is due, on the one hand, to its effect on the strength of dispersion interactions in the complex and, on the other hand, to the fact that it to some extent reflects the position of the upper filled orbitals of the solvent molecule. Both factors affect the degree of mixing of the π orbitals of the singlet oxygen molecule with the orbitals of the solvent molecule, which, as was found earlier, facilitates the activation of the a 1Δ g -b1Σ g + transition and the borrowing of its intensity by the a 1Δ g - X 3Σ g - transition.

Temperature Sensitive Singlet Oxygen Photosensitization by LOV-Derived Fluorescent Flavoproteins.

PubMed

Westberg, Michael; Bregnhøj, Mikkel; Etzerodt, Michael; Ogilby, Peter R

2017-03-30

Optogenetic sensitizers that selectively produce a given reactive oxygen species (ROS) constitute a promising tool for studying cell signaling processes with high levels of spatiotemporal control. However, to harness the full potential of this tool for live cell studies, the photophysics of currently available systems need to be explored further and optimized. Of particular interest in this regard, are the flavoproteins miniSOG and SOPP, both of which (1) contain the chromophore flavin mononucleotide, FMN, in a LOV-derived protein enclosure, and (2) photosensitize the production of singlet oxygen, O 2 (a 1 Δ g ). Here we present an extensive experimental study of the singlet and triplet state photophysics of FMN in SOPP and miniSOG over a physiologically relevant temperature range. Although changes in temperature only affect the singlet excited state photophysics slightly, the processes that influence the deactivation of the triplet excited state are more sensitive to temperature. Most notably, for both proteins, the rate constant for quenching of 3 FMN by ground state oxygen, O 2 (X 3 Σ g - ), increases ∼10-fold upon increasing the temperature from 10 to 43 °C, while the oxygen-independent channels of triplet state deactivation are less affected. As a consequence, this increase in temperature results in higher yields of O 2 (a 1 Δ g ) formation for both SOPP and miniSOG. We also show that the quantum yields of O 2 (a 1 Δ g ) production by both miniSOG and SOPP are mainly limited by the fraction of FMN triplet states quenched by O 2 (X 3 Σ g - ). The results presented herein provide a much-needed quantitative framework that will facilitate the future development of optogenetic ROS sensitizers.

Active-oxygen scavenging activity of plant extracts.

PubMed

Masaki, H; Sakaki, S; Atsumi, T; Sakurai, H

1995-01-01

To find antioxidative compounds present in plants, 65 types of plant extract were tested using the neotetrazolium method for evidence of superoxide anion-scavenging effects and 7 plant extracts were selected for further investigation. The activity of active-oxygen scavengers such as superoxide anion radicals, hydroxyl radicals, singlet oxygens and lipid peroxides in the 7 plant extracts (Aeseclus hippocastanum L., Hamamelis virginiana L. Polygonum cuspidatum Sieb., Quercus robur L., Rosemarinous officinalis L., Salvia officinalis L. and Sanguisorba officinalis L.) was examined in detail by both ESR spin-trapping and malondialdehyde generation. Furthermore, the active-oxygen scavenging activity of these plant extracts was evaluated using a murine dermal fibroblast culture system. Both Aeseclus hippocastanum L. and Hamamelis virginia L. were found to have strong active-oxygen scavenging activity of and protective activity against cell damage induced by active oxygen. Both Aeseclus hippocastanum L. and Hamamelis virginiana L. are proposed as potent plant extracts with potential application as anti-aging or anti-wrinkle material for the skin.

Time-resolved methods in biophysics. 7. Photon counting vs. analog time-resolved singlet oxygen phosphorescence detection.

PubMed

Jiménez-Banzo, Ana; Ragàs, Xavier; Kapusta, Peter; Nonell, Santi

2008-09-01

Two recent advances in optoelectronics, namely novel near-IR sensitive photomultipliers and inexpensive yet powerful diode-pumped solid-state lasers working at kHz repetition rate, enable the time-resolved detection of singlet oxygen (O2(a1Deltag)) phosphorescence in photon counting mode, thereby boosting the time-resolution, sensitivity, and dynamic range of this well-established detection technique. Principles underlying this novel approach and selected examples of applications are provided in this perspective, which illustrate the advantages over the conventional analog detection mode.

The participation of singlet oxygen in a photocitotoxicity of extract from amazon plant to cancer cells

NASA Astrophysics Data System (ADS)

Tcibulnikova, Anna V.; Degterev, Igor A.; Bryukhanov, Valery V.; Roberto, Mantuanelly M.; Campos Pereira, F. D.; Marin-Morales, M. A.; Slezhkin, Vasily A.; Samusev, Ilya G.

2018-01-01

We have been searching for new photosensitizers (PS) for photodynamic therapy (PDT) of cancer based on extracts from Amazonian plants since 2009. In this paper, we demonstrate that, under certain conditions, the extract from fruits of the Amazonian palm Euterpe oleraceae (popular name Açaí) can serve as a PS for PDT treatment of murine breast cancer cells (4T1 cell line). We have been first to show directly that the photodynamic effect of plant PS is due to singlet oxygen.

Dynamics of localized charges in dopamine-modified TiO{sub 2} and their effect on the formation of reactive oxygen species.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrijevic, N.; Rozhkova, E.; Rajh, T.

Modification of TiO{sub 2} nanoparticles with dopamine enables harvesting of visible light and promotes spatial separation of charges. The formation of reactive oxygen species (OH, {sup 1}O{sub 2}, O{sub 2}{sup -}, HO{sub 2}, H{sub 2}O{sub 2}) upon illumination of TiO{sub 2}/dopamine was studied using complementary spin-trap EPR and radical-induced fluorescence techniques. The localization of holes on dopamine suppresses oxidation of adsorbed water molecules at the surface of nanoparticles, and thus formation of OH radicals. At the same time, dopamine does not affect electronic properties of photogenerated electrons and their reaction with dissolved oxygen to produce superoxide anions. Superoxide anions aremore » proposed to generate singlet oxygen through dismutation reaction, resulting in a low yield of {sup 1}O{sub 2} detected.« less

Reactivity, chemoselectivity, and diastereoselectivity of the oxyfunctionalization of chiral allylic alcohols and derivatives in microemulsions: comparison of the chemical oxidation by the hydrogen peroxide/sodium molybdate system with the photooxygenation.

PubMed

Nardello, Véronique; Caron, Laurent; Aubry, Jean-Marie; Bouttemy, Sabine; Wirth, Thomas; Saha-Möller Chantu, R; Adam, Waldemar

2004-09-01

The chiral allylic alcohols 1a-d and their acetate (1e) and silyl ether (1f) derivatives have been oxidized by the H2O2/MoO4(2)- system, a convenient and efficient chemical source of singlet oxygen. This chemical peroxidation (formation of the allylic hydroperoxides 2) has been conducted in various media, which include aqueous solutions, organic solvents, and microemulsions. The reactivity, chemoselectivity, and diastereoselectivity of this chemical oxidation are compared to those of the sensitized photooxygenation, with the emphasis on preparative applications in microemulsion media. While a similar threo diastereoselectivity is observed for both modes of peroxidation, the chemoselectivity differs significantly, since in the chemical oxidation with the H2O2/MoO4(2)- system the undesirable epoxidation by the intermediary peroxomolybdate competes efficiently with the desirable peroxidation by the in situ generated singlet oxygen. A proper choice of the type of microemulsion and the reaction conditions furnishes a high chemoselectivity (up to 97%) in favor of threo-diastereoselective (up to 92%) peroxidation. Copyright 2004 American Chemical Society

pH-Responsive Dimeric Zinc(II) Phthalocyanine in Mesoporous Silica Nanoparticles as an Activatable Nanophotosensitizing System for Photodynamic Therapy.

PubMed

Wong, Roy C H; Chow, Sun Y S; Zhao, Shirui; Fong, Wing-Ping; Ng, Dennis K P; Lo, Pui-Chi

2017-07-19

An acid-cleavable acetal-linked zinc(II) phthalocyanine dimer with an azido terminal group (cPc) was prepared and conjugated to alkyne-modified mesoporous silica nanoparticles via copper(I)-catalyzed alkyne-azide cycloaddition reaction. For comparison, an amine-linked analogue (nPc) was also prepared as a non-acid-cleavable counterpart. These dimeric phthalocyanines were significantly self-quenched due to the close proximity of the phthalocyanine units inside the mesopores, resulting in much weaker fluorescence emission and singlet oxygen generation, both in N,N-dimethylformamide and in phosphate-buffered saline (PBS), compared with the free molecular counterparts. Under acidic conditions in PBS, the cPc-encapsulated nanosystem was activated in terms of fluorescence emission and singlet oxygen production. After internalization into human colon adenocarcinoma HT29 cells, it exhibited much higher intracellular fluorescence and photocytotoxicity compared to the nanosystem entrapped with nPc. The activation of this nanosystem was also demonstrated in tumor-bearing nude mice. The intratumoral fluorescence intensity increased gradually over 24 h, while for the nPc counterpart the fluorescence remained very weak. The results suggest that this nanosystem serves as a promising activatable nanophotosensitizing agent for photodynamic therapy.

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

NASA Astrophysics Data System (ADS)

Nayak, Gaurav; Santos Sousa, João; Bruggeman, Peter J.

2017-03-01

The production of singlet delta oxygen (O2(a 1Δg)) is of growing interest for many applications. We report on the measurement of O2(a 1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a 1Δg) production. Different O2(a 1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a 1Δg) densities are discussed. The flow rate also allows for control of the O2(a 1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

Lutetium(III) acetate phthalocyanines for photodynamic therapy applications: Synthesis and photophysicochemical properties.

PubMed

Mantareva, Vanya; Durmuş, Mahmut; Aliosman, Meliha; Stoineva, Ivanka; Angelov, Ivan

2016-06-01

The development of new water-soluble photosensitizers for photodynamic therapy (PDT) applications is a very active research topic. Efforts have been made to obtain the far-red absorbing phthalocyanine complexes with molecular design that facilitates the uptake and selectivity for a high PDT efficiency. The monomolecular lutetium(III) acetate phthalocyanines (LuPcs) substituted with methylpyridyloxy groups at non-peripheral (5) and peripheral (6) positions were synthesized by following the modification of the well-known synthetical routes. The photo-physicochemical properties of the both quaternized LuPcs were evaluated by the steady-state and time-resolved spectroscopy. The photochemical technique was applied to study the generation of the singlet oxygen. Two water-soluble and cationic LuPcs were synthesized and chemically characterized. The photo-physicochemical properties of absorption (675 and 685nm) and the red shifted fluorescence (704 and 721nm) as well as the fluorescence lifetimes (2.24 and 3.27ns) were studied. The promising values of singlet oxygen quantum yields (0.32 for 5 and 0.35 for 6) were determined. Lutetium(III) acetate phthalocyanine complexes were synthesized and evaluated with physicochemical properties suitable for future photodynamic therapy applications. Copyright © 2016 Elsevier B.V. All rights reserved.

DNA repair inhibition by UVA photoactivated fluoroquinolones and vemurafenib

PubMed Central

Peacock, Matthew; Brem, Reto; Macpherson, Peter; Karran, Peter

2014-01-01

Cutaneous photosensitization is a common side effect of drug treatment and can be associated with an increased skin cancer risk. The immunosuppressant azathioprine, the fluoroquinolone antibiotics and vemurafenib—a BRAF inhibitor used to treat metastatic melanoma—are all recognized clinical photosensitizers. We have compared the effects of UVA radiation on cultured human cells treated with 6-thioguanine (6-TG, a DNA-embedded azathioprine surrogate), the fluoroquinolones ciprofloxacin and ofloxacin and vemurafenib. Despite widely different structures and modes of action, each of these drugs potentiated UVA cytotoxicity. UVA photoactivation of 6-TG, ciprofloxacin and ofloxacin was associated with the generation of singlet oxygen that caused extensive protein oxidation. In particular, these treatments were associated with damage to DNA repair proteins that reduced the efficiency of nucleotide excision repair. Although vemurafenib was also highly phototoxic to cultured cells, its effects were less dependent on singlet oxygen. Highly toxic combinations of vemurafenib and UVA caused little protein carbonylation but were nevertheless inhibitory to nucleotide excision repair. Thus, for three different classes of drugs, photosensitization by at least two distinct mechanisms is associated with reduced protection against potentially mutagenic and carcinogenic DNA damage. PMID:25414333

Singlet oxygen generation of photosensitizers effectively activated by Nd3+-doped upconversion nanoparticles of luminescence intensity enhancing with shell thickness decreasing

NASA Astrophysics Data System (ADS)

Zou, Haixia; Jin, Fengmin; Song, Xiaoyan; Xing, Jinfeng

2017-04-01

The introduction of a thick shell structure has been widely used to enhance the emission intensity of upconversion nanoparticles (UCNPs). However, a thick shell could increase the distance between UCNPs and photosensitizers, which is not favourable to the generation of singlet oxygen (1O2) in photodynamic therapy (PDT) due to the low fluorescence resonance energy transfer (FRET) efficiency. In this study, we used a facile method to prepare UCNPs that the emission intensity could increase with the shell thickness decreasing, which facilitated the efficient FRET between UCNPs and photosensitizers. In detail, the Nd3+-doped UCNPs with different dopant concentration of Yb3+ were prepared and characterized firstly. The Ir/g (intensity of red luminescence to green luminescence) was tuned to increase largely by precisely controlling Yb3+ concentration in core-shell, which could make UCNPs effectively activate methylene blue (MB). Then, a unique procedure was used to prepare NaYF4:Yb/Er/Nd@NaYF4:Nd (Yb3+:30%) core-shell nanoparticles with different shell thickness by tuning the amount of the core. The upconversion luminescence (UCL) intensity of those UCNPs enhanced dramatically with the shell thickness decreasing. Furthermore, UCNPs and MB were encapsulated into SiO2 nanoparticles. FRET efficiency between UCNPs and MB largely increased with the shell thickness of UCNPs decreasing. Correspondingly, the efficiency of 1O2 generation obviously increased. We provided a new method to optimize the UCL intensity and FRET efficiency at the same time to produce 1O2 efficiently.

Ubiquitin facilitates a quality-control pathway that removes damaged chloroplasts

DOE PAGES

Woodson, Jesse D.; Joens, Matthew S.; Sinson, Andrew B.; ...

2015-10-23

Energy production by chloroplasts and mitochondria causes constant oxidative damage. A functioning photosynthetic cell requires quality-control mechanisms to turn over and degrade chloroplasts damaged by reactive oxygen species (ROS). Here in this study, we generated a conditionally lethal Arabidopsis mutant that accumulated excess protoporphyrin IX in the chloroplast and produced singlet oxygen. Damaged chloroplasts were subsequently ubiquitinated and selectively degraded. A genetic screen identified the plant U-box 4 (PUB4) E3 ubiquitin ligase as being necessary for this process. pub4-6 mutants had defects in stress adaptation and longevity. As a result, we have identified a signal that leads to the targetedmore » removal of ROS-overproducing chloroplasts.« less

Regulation of transepithelial ion transport by intracellular calcium ions.

PubMed

Cuthbert, A W

1985-01-01

A photodynamic effect of erythrosine B on the basolateral surface of rat colon epithelium under short circuit conditions is described. The resulting irreversible increase in short circuit current was the result of electrogenic chloride secretion. The effect was dependent upon oxygen and calcium ions, and is probably due to the generation of singlet oxygen which then permeabilises the membranes to calcium. Half maximal activation of secretion in permeabilised preparations occurred at an external calcium concentration of 1 microM. In tight sodium transporting epithelia increased Cai reduces SCC, possibly by a direct effect on apical sodium permeability. In toad urinary bladder SCC fell in response to conditions outlined above for rat colon.

Ubiquitin facilitates a quality-control pathway that removes damaged chloroplasts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woodson, Jesse D.; Joens, Matthew S.; Sinson, Andrew B.

Energy production by chloroplasts and mitochondria causes constant oxidative damage. A functioning photosynthetic cell requires quality-control mechanisms to turn over and degrade chloroplasts damaged by reactive oxygen species (ROS). Here in this study, we generated a conditionally lethal Arabidopsis mutant that accumulated excess protoporphyrin IX in the chloroplast and produced singlet oxygen. Damaged chloroplasts were subsequently ubiquitinated and selectively degraded. A genetic screen identified the plant U-box 4 (PUB4) E3 ubiquitin ligase as being necessary for this process. pub4-6 mutants had defects in stress adaptation and longevity. As a result, we have identified a signal that leads to the targetedmore » removal of ROS-overproducing chloroplasts.« less

Scheme for generating the singlet state of three atoms trapped in distant cavities coupled by optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dong-Yang; Wen, Jing-Ji; Bai, Cheng-Hua

2015-09-15

An effective scheme is proposed to generate the singlet state with three four-level atoms trapped in three distant cavities connected with each other by three optical fibers, respectively. After a series of appropriate atom–cavity interactions, which can be arbitrarily controlled via the selective pairing of Raman transitions and corresponding optical switches, a three-atom singlet state can be successfully generated. The influence of atomic spontaneous decay, photon leakage of cavities and optical fibers on the fidelity of the state is numerically simulated showing that the three-atom singlet state can be generated with high fidelity by choosing the experimental parameters appropriately.

On the O2(a1Δ) quenching by vibrationally excited ozone

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Mikheyev, P. A.; Heaven, M. C.

2010-09-01

The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen (O2(a)) in electric discharge. It is important to understand the mechanisms by which O2(a) is quenched in these devices. To gain understanding of this mechanisms quenching of O2(a) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a) quenching were followed by observing the 1268 nm fluorescence of the O2 a --> X transition. Fast quenching of O2(a) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

Luteolin as reactive oxygen generator by X-ray and UV irradiation

NASA Astrophysics Data System (ADS)

Toyama, Michiru; Mori, Takashi; Takahashi, Junko; Iwahashi, Hitoshi

2018-05-01

Non-toxic X-ray-responsive substances can be used in the radiosensitization of cancer, like porphyrin mediated radiotherapy. However, most X-ray-responsive substances are toxic. To find novel non-toxic X-ray-responsive substances, we studied the X-ray and UV reactivity of 40 non-toxic compounds extracted from plants. Dihydroethidium was used as an indicator to detect reactive oxygen species (ROS) generated by the compounds under X-ray or UV irradiation. We found that 13 of the investigated compounds generated ROS under X-ray irradiation and 17 generated ROS under UV irradiation. Only 4 substances generated ROS under both X-ray and UV. In particular, luteolin exhibited the highest activity among the investigated compounds; therefore, the ROS generated by luteolin were thoroughly characterized. To identify the ROS, we employed a combination of ROS detection reagents and their quenchers. O2·- generation by luteolin was monitored using dihydroethidium and superoxide dismutase (as an O2·- quencher). OH· and 1O2 generation was determined using aminophenyl fluorescein with ethanol (OH· quencher) and Singlet Oxygen Sensor Green® with NaN3 (1O2 quencher), respectively. Generation of O2·- under X-ray and UV irradiation was observed; however, no OH· or 1O2 was detected. The production of ROS from luteolin is surprising, because luteolin is a well-known antioxidant.

Dictating photoreactivity through restricted bond rotations: cross-photoaddition of atropisomeric acrylimide derivatives under UV/visible-light irradiation.

PubMed

Iyer, Akila; Jockusch, Steffen; Sivaguru, J

2014-11-13

Nonbiaryl atropisomeric acrylimides underwent facile [2 + 2] photocycloaddition leading to cross-cyclobutane adducts with very high stereospecificity (enantiomeric excess (ee): 99% and diastereomeric excess (de): 99%). The photoreactions proceeded smoothly in isotropic media for both direct and triplet sensitized irradiations. The reactions were also found to be very efficient in the solid state where the same cross-cyclobutane adduct was observed. Photophysical studies enabled us to understand the excited-state photochemistry of acrylimides. The triplet energy was found to be ∼63 kcal/mol. The reactions proceeded predominantly via a singlet excited state upon direct irradiation with very poor intersystem crossing that was ascertained by quantification of the generated singlet oxygen. The reactions progressed smoothly with triplet sensitization with UV or visible-light irradiations. Laser flash photolysis experiments established the triplet transient of atropisomeric acrylimides with a triplet lifetime at room temperature of ∼40 ns.

A Possible Role for Singlet Oxygen in the Degradation of Various Antioxidants. A Meta-Analysis and Review of Literature Data

PubMed Central

Petrou, Athinoula L.; Petrou, Petros L.; Ntanos, Theodoros; Liapis, Antonis

2018-01-01

The thermodynamic parameters Eact, ΔH≠, ΔS≠, and ΔG≠ for various processes involving antioxidants were calculated using literature kinetic data (k, T). The ΔG≠ values of the antioxidants’ processes vary in the range 91.27–116.46 kJmol−1 at 310 K. The similarity of the ΔG≠ values (for all of the antioxidants studied) is supported to be an indication that a common mechanism in the above antioxidant processes may be taking place. A value of about 10–30 kJmol−1 is the activation energy for the diffusion of reactants depending on the reaction and the medium. The energy 92 kJmol−1 is needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen). We suggest the same role of the oxidative stress and specifically of singlet oxygen to the processes of antioxidants as in the processes of proteinaceous diseases. We therefore suggest a competition between the various antioxidants and the proteins of proteinaceous diseases in capturing singlet oxygen’s empty π* orbital. The concentration of the antioxidants could be a crucial factor for the competition. Also, the structures of the antioxidant molecules play a significant role since the various structures have a different number of regions of high electron density. PMID:29495515

REMPI detection of singlet oxygen 1O2 arising from UV-photodissociation of van der Waals complex isoprene-oxygen C5H8-O2

NASA Astrophysics Data System (ADS)

Bogomolov, Alexandr S.; Dozmorov, Nikolay V.; Kochubei, Sergei A.; Baklanov, Alexey V.

2018-01-01

The one-laser two-color resonance enhanced multiphoton ionization REMPI [(1 + 1‧) + 1] and velocity map imaging have been applied to investigate formation of molecular oxygen in excited singlet O2(a1Δg) and ground O2(X3Σg-) states in the photodissociation of van der Waals complex isoprene-oxygen C5H8-O2. These molecules were found to appear in the different rotational states with translational energy varied from a value as low as ∼1 meV to a distribution with temperature of about 940 K. The observed traces of electron recoil in the images of photoions reveal participation of several ionization pathways of the resonantly excited intermediate states of O2.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Centrifugal bubble O2 (1Δ) gas generator with a total pressure of 100 Torr

NASA Astrophysics Data System (ADS)

Zagidulin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.

2008-08-01

A centrifugal bubbling singlet-oxygen gas generator is developed in which chlorine with helium are injected into the rotating layer of the alkali solution of hydrogen peroxide through cylindrical nozzles directed at an angle of 30° to the bubbler surface. The concentrations of water vapour and O2 (1Δ) and the gas temperature were determined by using the multichannel recording of the emission bands of oxygen at 634, 703, 762 and 1268 nm. For the chlorine and helium flow rates of 60 and 90 mmol s-1, respectively, the specific chlorine load of 3.2 mmol cm-2, a total pressure of 100 Torr in the working region of the gas generator and the oxygen partial pressure of 36 Torr, the chlorine utilisation was 90% and the content of O2 (1Δ) was ≈60%. For the ratio of the flow rates of chlorine and the alkali solution of hydrogen peroxide equal to 1 mol L-1, the water vapour content was ≈25%. The chemical efficiency of the oxygen—iodine laser with this gas generator achieved 23% for the specific power of 12.7 W cm per 1 cm3 s-1 per pass of the solution through the gas generator.

Deciphering early events involved in hyperosmotic stress-induced programmed cell death in tobacco BY-2 cells.

PubMed

Monetti, Emanuela; Kadono, Takashi; Tran, Daniel; Azzarello, Elisa; Arbelet-Bonnin, Delphine; Biligui, Bernadette; Briand, Joël; Kawano, Tomonori; Mancuso, Stefano; Bouteau, François

2014-03-01

Hyperosmotic stresses represent one of the major constraints that adversely affect plants growth, development, and productivity. In this study, the focus was on early responses to hyperosmotic stress- (NaCl and sorbitol) induced reactive oxygen species (ROS) generation, cytosolic Ca(2+) concentration ([Ca(2+)]cyt) increase, ion fluxes, and mitochondrial potential variations, and on their links in pathways leading to programmed cell death (PCD). By using BY-2 tobacco cells, it was shown that both NaCl- and sorbitol-induced PCD seemed to be dependent on superoxide anion (O2·(-)) generation by NADPH-oxidase. In the case of NaCl, an early influx of sodium through non-selective cation channels participates in the development of PCD through mitochondrial dysfunction and NADPH-oxidase-dependent O2·(-) generation. This supports the hypothesis of different pathways in NaCl- and sorbitol-induced cell death. Surprisingly, other shared early responses, such as [Ca(2+)]cyt increase and singlet oxygen production, do not seem to be involved in PCD.

Size-engineered biocompatible polymeric nanophotosensitizer for locoregional photodynamic therapy of cancer.

PubMed

Jeong, Keunsoo; Park, Solji; Lee, Yong-Deok; Kang, Chi Soo; Kim, Hyun Jun; Park, Hyeonjong; Kwon, Ick Chan; Kim, Jungahn; Park, Chong Rae; Kim, Sehoon

2016-08-01

Current approaches in use of water-insoluble photosensitizers for photodynamic therapy (PDT) of cancer often demand a nano-delivery system. Here, we report a photosensitizer-loaded biocompatible nano-delivery formulation (PPaN-20) whose size was engineered to ca. 20nm to offer improved cell/tissue penetration and efficient generation of cytotoxic singlet oxygen. PPaN-20 was fabricated through the physical assembly of all biocompatible constituents: pyropheophorbide-a (PPa, water-insoluble photosensitizer), polycaprolactone (PCL, hydrophobic/biodegradable polymer), and Pluronic F-68 (clinically approved polymeric surfactant). Repeated microemulsification/evaporation method resulted in a fine colloidal dispersion of PPaN-20 in water, where the particulate PCL matrix containing well-dispersed PPa molecules inside was stabilized by the Pluronic corona. Compared to a control sample of large-sized nanoparticles (PPaN-200) prepared by a conventional solvent displacement method, PPaN-20 revealed optimal singlet oxygen generation and efficient cellular uptake by virtue of the suitably engineered size and constitution, leading to high in vitro phototoxicity against cancer cells. Upon administration to tumor-bearing mice by peritumoral route, PPaN-20 showed efficient tumor accumulation by the enhanced cell/tissue penetration evidenced by in vivo near-infrared fluorescence imaging. The in vivo PDT treatment with peritumorally administrated PPaN-20 showed significantly enhanced suppression of tumor growth compared to the control group, demonstrating great potential as a biocompatible photosensitizing agent for locoregional PDT treatment of cancer. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of high yielding photonic light delivery system for photodynamic therapy of esophageal carcinomas

NASA Astrophysics Data System (ADS)

Premasiri, Amaranath; Happawana, Gemunu; Rosen, Arye

2007-02-01

Photodynamic therapy (PDT) is an approved treatment modality for Barrett's and invasive esophageal carcinoma. Proper Combination of photosentizing agent, oxygen, and a specific wavelength of light to activate the photosentizing agents is necessary for the cytotoxic destruction of cancerous cells by PDT. As a light source expensive solid-state laser sources currently are being used for the treatment. Inexpensive semiconductor lasers have been suggested for the light delivery system, however packaging of semiconductor lasers for optimal optical power output is challenging. In this paper, we present a multidirectional direct water-cooling of semiconductor lasers that provides a better efficiency than the conventional unidirectional cooling. AlGaAsP lasers were tested under de-ionized (DI) water and it is shown that the optical power output of the lasers under the DI water is much higher than that of the uni-directional cooling of lasers. Also, in this paper we discuss how direct DI water-cooling can optimize power output of semiconductor lasers. Thereafter an optimal design of the semiconductor laser package is shown with the DI water-cooling system. Further, a microwave antenna is designed which is to be imprinted on to a balloon catheter in order to provide local heating of esophagus, leading to an increase in local oxygenation of the tumor to generate an effective level of singlet oxygen for cellular death. Finally the optimal level of light energy that is required to achieve the expected level of singlet oxygen is modeled to design an efficient PDT protocol.

Macroscopic singlet oxygen modeling for dosimetry of Photofrin-mediated photodynamic therapy: an in-vivo study

NASA Astrophysics Data System (ADS)

Qiu, Haixia; Kim, Michele M.; Penjweini, Rozhin; Zhu, Timothy C.

2016-08-01

Although photodynamic therapy (PDT) is an established modality for cancer treatment, current dosimetric quantities, such as light fluence and PDT dose, do not account for the differences in PDT oxygen consumption for different fluence rates (φ). A macroscopic model was adopted to evaluate using calculated reacted singlet oxygen concentration ([) to predict Photofrin-PDT outcome in mice bearing radiation-induced fibrosarcoma tumors, as singlet oxygen is the primary cytotoxic species responsible for cell death in type II PDT. Using a combination of fluences (50, 135, 200, and 250 J/cm2) and φ (50, 75, and 150 mW/cm2), tumor regrowth rate, k, was determined for each condition. A tumor cure index, CI=1-k/k, was calculated based on the k between PDT-treated groups and that of the control, k. The measured Photofrin concentration and light dose for each mouse were used to calculate PDT dose and [, while mean optical properties (μa=0.9 cm-1, μs‧=8.4 cm-1) were used to calculate φ for all mice. CI was correlated to the fluence, PDT dose, and [ with R2=0.35, 0.79, and 0.93, respectively. These results suggest that [ serves as a better dosimetric quantity for predicting PDT outcome.

Different mechanisms for the photoinduced production of oxidative DNA damage by fluoroquinolones differing in photostability.

PubMed

Spratt, T E; Schultz, S S; Levy, D E; Chen, D; Schlüter, G; Williams, G M

1999-09-01

Several fluoroquinolone antibacterial agents exhibit an adverse phototoxic effect in humans and are photo-cocarcinogenic in mice. The UV-induced production of reactive oxygen species plays a role in the toxicity and may be involved in carcinogenicity. Four fluoroquinolones were examined for the ability to photochemically produce oxidative damage in naked DNA. The major structural difference in the fluoroquinolones that would have an effect on their photostability is the functionality at the 8-position. At this position, 1-cyclopropyl-7-(2,8-diazbicyclo[4.3.0]non-8-yl)-6, 8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (BAY y3118) contains a chlorine atom, lomefloxacin a fluorine atom, ciprofloxacin a proton, and moxifloxacin a methoxy group. The formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in calf thymus DNA was assessed by HPLC with electrochemical detection, and strand breaks were measured in pBR322 with agarose gel electrophoresis. The relative photolability of the fluoroquinolones correlated to the extent of production of 8-oxodGuo and strand breaks, with both UVA and UVB irradiation, in the following order: BAY y3118 approximately lomefloxacin > ciprofloxacin > moxifloxacin. Experiments were performed to determine whether the mechanism of damage was due to a type I (radical) or type II (singlet oxygen) pathway. Nitrogen depletion of oxygen resulted in a decrease in the extent of formation of 8-oxodGuo, suggesting that oxygen was involved. The use of selective radical or singlet oxygen inhibitors was inconclusive with respect to which pathway was involved. The use of D(2)O as a solvent, which would extend the lifetime of singlet oxygen, suggested that this species is involved in the formation of 8-oxodGuo by moxifloxacin and ciprofloxacin, but not by lomefloxacin and BAY y3118. Similarly, it was found that singlet oxygen was not involved in strand break formation. Thus, the evidence suggests that fluoroquinolones can photochemically produce DNA damage by both type I and type II mechanisms.

Novel foamy origin for singlet fermion masses

NASA Astrophysics Data System (ADS)

Ellis, John; Mavromatos, Nick E.; Nanopoulos, Dimitri V.

2017-10-01

We show how masses for singlet fermions can be generated by interactions with a D-particle model of space-time foam inspired by brane theory. It has been shown previously by one of the authors (N. E. M.) that such interactions may generate dynamically small masses for charged fermions via the recoils of D-particle defects interacting with photons. In this work we consider the direct interactions of D-particle with uncharged singlet fermions such as right-handed neutrinos. Quantum fluctuations of the lattice of D-particles have massless vector (spin-one) excitations that are analogues of phonons. These mediate forces with the singlet fermions, generating large dynamical masses that may be communicated to light neutrinos via the seesaw mechanism.

Effect of exogenous hydrogen peroxide on biophoton emission from radish root cells.

PubMed

Rastogi, Anshu; Pospísil, Pavel

2010-01-01

Biophotons spontaneously emitted from radish root cells were detected using highly sensitive photomultiplier tube. Freshly isolated radish root cells exhibited spontaneous photon emission of about 4 counts s(-1). Addition of hydrogen peroxide to the cells caused significant enhancement in biophoton emission to about 500 counts s(-1). Removal of molecular oxygen using glucose/glucose oxidase system and scavengering of reactive oxygen species by reducing agents such are sodium ascorbate and cysteine completely diminished biophoton emission. Spectral analysis of the hydrogen peroxide-induced biophoton emission indicates that biophotons are emitted mainly in green-red region of the spectra. The data provided by electron paramagnetic resonance spin-trapping technique showed that formation of singlet oxygen observed after addition of H2O2 correlates with enhancement in biophoton emission. These observations provide direct evidence that singlet oxygen is involved in biophoton emission from radish root cells. Copyright 2010 Elsevier Masson SAS. All rights reserved.

Reactions of PO(x)Cl(y)-ions with O(2)(a1-delta-g), H(2)O, and Cl(2) at 298 K

DTIC Science & Technology

2008-03-10

branching ratio values calculated in this way for the 02(X) reaction differ slightly from the previous SIFT measurement [17]. However, the difference is...been measured in a selected ion flow tube (SIFT) at 298 K. A mixture of 02(a’Ag) in 02 has been produced using a recently designed chemical singlet...oxygen generator (sparger) with an emission detection scheme adopted previously in our laboratory. The experiments continue a series of investigations

Fructose as a novel photosensitizer: Characterization of reactive oxygen species and an application in degradation of diuron and chlorpyrifos.

PubMed

Nayak, Shaila; Muniz, Juan; Sales, Christopher M; Tikekar, Rohan V

2016-02-01

The objective of this study was to identify reactive oxygen species (ROS) generated from the exposure of fructose solution to the 254 nm ultraviolet (UV) light and evaluate whether fructose can be used as a photosensitizer for accelerated photo-degradation of diuron and chlorpyrifos. We demonstrated that hydrogen peroxide, singlet oxygen ((1)O2) and acidic photolysis products were generated upon UV exposure of fructose. Consistent with these findings, UV induced degradation of chlorpyrifos and diuron was accelerated by the presence of 500 mM fructose. The average first order photo-degradation rate constants in the absence and presence of 500 mM fructose were 0.92 and 2.07 min(-1) respectively for diuron and 0.04 and 0.07 min(-1) for chlorpyrifos. The quantum yields (ɸ) for direct photo-degradation of diuron and chlorpyrifos were 0.003 and 0.001 respectively. In the presence of 500 mM fructose, these values increased to 0.006 and 0.002 respectively. Thus, fructose may be an effective photosensitizer. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cytotoxicity of All-Trans-Retinal Increases Upon Photodegradation†

PubMed Central

Różanowska, Małgorzata; Handzel, Kinga; Boulton, Michael E.; Różanowski, Bartosz

2013-01-01

All-trans-retinal (AtRal) can accumulate in the retina as a result of excessive exposure to light. The purpose of this study was to compare cytotoxicity of AtRal and photodegraded AtRal (dAtRal) on cultured human retinal pigment epithelial cells in dark and upon exposure to visible light. AtRal was degraded by exposure to visible light. Cytotoxicity was monitored by imaging of cell morphology, propidium iodide staining of cells with permeable plasma membrane and measurements of reductive activity of cells. Generation of singlet oxygen photosensitized by AtRal and dAtRal was monitored by time-resolved measurements of characteristic singlet oxygen phosphorescence. Photodegradation of AtRal resulted in a decrease in absorption of visible light and accumulation of the degradation products with absorption maximum at ~330 nm. Toxicity of dAtRal was concentration-dependent and was greater during irradiation with visible light than in dark. DAtRal was more cytotoxic than AtRal both in dark and during exposure to visible light. Photochemical properties of dAtRal indicate that it may be responsible for the maximum in the action spectra of retinal photodamage recorded in animals. In conclusion, photodegradation products of AtRal may impose a significant threat to the retina and therefore their roles in retinal pathology need to be explored. PMID:22515697

Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen.

PubMed

Mahne, Nika; Renfrew, Sara E; McCloskey, Bryan D; Freunberger, Stefan A

2018-05-04

Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal-O 2 batteries, and are believed to form and decompose reversibly in metal-O 2 /CO 2 cells. In these cathodes, Li 2 CO 3 decomposes to CO 2 when exposed to potentials above 3.8 V vs. Li/Li + . However, O 2 evolution, as would be expected according to the decomposition reaction 2 Li 2 CO 3 →4 Li + +4 e - +2 CO 2 +O 2 , is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen ( 1 O 2 ) forms upon oxidizing Li 2 CO 3 in an aprotic electrolyte and therefore does not evolve as O 2 . These results have substantial implications for the long-term cyclability of batteries: they underpin the importance of avoiding 1 O 2 in metal-O 2 batteries, question the possibility of a reversible metal-O 2 /CO 2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition-metal cathodes with residual Li 2 CO 3 . © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Monte Carlo modeling of in vivo protoporphyrin IX fluorescence and singlet oxygen production during photodynamic therapy for patients presenting with superficial basal cell carcinomas

NASA Astrophysics Data System (ADS)

Valentine, Ronan M.; Brown, C. Tom A.; Moseley, Harry; Ibbotson, Sally; Wood, Kenny

2011-04-01

We present protoporphyrin IX (PpIX) fluorescence measurements acquired from patients presenting with superficial basal cell carcinoma during photodynamic therapy (PDT) treatment, facilitating in vivo photobleaching to be monitored. Monte Carlo (MC) simulations, taking into account photobleaching, are performed on a three-dimensional cube grid, which represents the treatment geometry. Consequently, it is possible to determine the spatial and temporal changes to the origin of collected fluorescence and generated singlet oxygen. From our clinical results, an in vivo photobleaching dose constant, β of 5-aminolaevulinic acid-induced PpIX fluorescence is found to be 14 +/- 1 J/cm2. Results from our MC simulations suggest that an increase from our typical administered treatment light dose of 75-150 J/cm2 could increase the effective PDT treatment initially achieved at a depth of 2.7-3.3 mm in the tumor, respectively. Moreover, this increase reduces the surface PpIX fluorescence from 0.00012 to 0.000003 of the maximum value recorded before treatment. The recommendation of administrating a larger light dose, which advocates an increase in the treatment time after surface PpIX fluorescence has diminished, remains valid for different sets of optical properties and therefore should have a beneficial outcome on the total treatment effect.

A Nanosystem Capable of Releasing a Photosensitizer Bioprecursor under Two‐Photon Irradiation for Photodynamic Therapy

PubMed Central

Wu, Hao; Zeng, Fang; Zhang, Hang; Xu, Jiangsheng

2015-01-01

The applications of photodynamic therapy (PDT) are usually limited by photosensitizers' side effects and singlet oxygen's short half‐life. Herein, a mitochondria‐targeted nanosystem is demonstrated to enhance the PDT efficacy by releasing a bio‐precursor of photosensitizer under two‐photon irradiation. A phototriggerable coumarin derivative is first synthesized by linking 5‐aminolevulinic acid (5‐ALA, the bio‐precursor) to coumarin; and the nanosystem (CD‐ALA‐TPP) is then fabricated by covalently incorporating this coumarin derivative and a mitochondria‐targeting compound triphenylphosphonium (TPP) onto carbon dots (CDs). Upon cellular internalization, the nanosystem preferentially accumulates in mitochondria; and under one‐ or two‐photon irradiation, it releases 5‐ALA molecules that are then metabolized into protoporphyrin IX in mitochondria through a series of biosynthesis processes. The subsequent red light irradiation induces this endogenously synthesized photosensitizer to generate singlet oxygen, thereby causing oxidant damage to mitochondria and then the apoptosis of the cells. Analysis via 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assays indicate that the novel PDT system exhibits enhanced cytotoxicity toward cancer cells. This study may offer a new strategy for designing PDT systems with high efficacy and low side effects. PMID:27774388

Protection by Isoprene against Singlet Oxygen in Leaves

PubMed Central

Affek, Hagit P.; Yakir, Dan

2002-01-01

Isoprene (2-methyl-1,3-butadiene) protection against effects of singlet oxygen was investigated in Myrtus communis and Rhamnus alaternus. In M. communis, singlet oxygen produced in the leaves by Rose Bengal (RB) led to a 65% decrease in net assimilation rates within 3 h, whereas isoprene emission rates showed either a 30% decrease at ambient CO2 concentrations or a 70% increase under high CO2. In both cases, these changes led to an increase in calculated internal isoprene concentrations. The isoprene protection effect was directly demonstrated by fumigation of young (non-emitting) leaves, treated with RB or bromoxynil (simulating photoinhibition). There was 42% and 29% reduction in the damage to net assimilation compared with non-fumigated leaves for RB or bromoxynil, respectively. In R. alaternus, similar effects of RB on net assimilation were observed, and additional fluorescence measurements showed a significantly smaller decrease in Fv/Fm in isoprene-fumigated young leaves treated with RB (from 0.78 to 0.52), compared with non-fumigated leaves (from 0.77 to 0.27). The internal isoprene concentrations used in this study and possible rate of 1O2 production in leaves indicate that the protective effects observed should be beneficial also under natural conditions. PMID:12011357

In situ characterization of the oxidative degradation of a polymeric light emitting device

NASA Astrophysics Data System (ADS)

Cumpston, B. H.; Parker, I. D.; Jensen, K. F.

1997-04-01

Light-emitting devices with polymeric emissive layers have great promise for the production of large-area, lightweight, flexible color displays, but short lifetimes currently limit applications. We address mechanisms of bulk polymer degradation in these devices and show through in situ Fourier transform infrared characterization of working light-emitting devices with active layers of poly[2-methoxy,5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] that oxygen is responsible for the degradation of the polymer film. A mechanism is given based on the formation of singlet oxygen from oxygen impurities in the film via energy transfer from a nonradiative exciton. Fourier transform infrared and x-ray photoelectron spectroscopy results are consistent with the mechanism, involving singlet oxygen attack followed by free radical processes. We further show that oxygen readily diffuses into the active polymer layer, changing the electrical characteristics of the film even at low concentrations. Thus, polyphenylene-vinylene-based light-emitting devices will self-destruct during operation if fabricated without special attention to eliminating oxygen contamination during fabrication and device operation.

Singlet oxygen-sensitized delayed fluorescence of common water-soluble photosensitizers.

PubMed

Scholz, Marek; Dědic, Roman; Breitenbach, Thomas; Hála, Jan

2013-10-01

Six common water-soluble singlet oxygen ((1)O2) photosensitizers - 5,10,15,20-tetrakis(1-methyl-4-pyridinio) porphine (TMPyP), meso-tetrakis(4-sulfonathophenyl)porphine (TPPS4), Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4), eosin Y, rose bengal, and methylene blue - were investigated in terms of their ability to produce delayed fluorescence (DF) in solutions at room temperature. All the photosensitizers dissolved in air-saturated phosphate buffered saline (PBS, pH 7.4) exhibit easily detectable DF, which can be nearly completely quenched by 10 mM NaN3, a specific (1)O2 quencher. The DF kinetics has a biexponential rise-decay character in a microsecond time domain. Therefore, we propose that singlet oxygen-sensitized delayed fluorescence (SOSDF), where the triplet state of a photosensitizer reacts with (1)O2 giving rise to an excited singlet state of the photosensitizer, is the prevailing mechanism. It was confirmed by additional evidence, such as a monoexponential decay of triplet-triplet transient absorption kinetics, dependence of SOSDF kinetics on oxygen concentration, absence of SOSDF in a nitrogen-saturated sample, or the effect of isotopic exchange H2O-D2O. Eosin Y and AlPcS4 show the largest SOSDF quantum yield among the selected photosensitizers, whereas rose bengal possesses the highest ratio of SOSDF intensity to prompt fluorescence intensity. The rate constant for the reaction of triplet state with (1)O2 giving rise to the excited singlet state of photosensitizer was estimated to be ~/>1 × 10(9) M(-1) s(-1). SOSDF kinetics contains information about both triplet and (1)O2 lifetimes and concentrations, which makes it a very useful alternative tool for monitoring photosensitizing and (1)O2 quenching processes, allowing its detection in the visible spectral region, utilizing the photosensitizer itself as a (1)O2 probe. Under our experimental conditions, SOSDF was up to three orders of magnitude more intense than the infrared (1)O2 phosphorescence and by far the most important pathway of DF. SOSDF was also detected in a suspension of 3T3 mouse fibroblast cells, which underlines the importance of SOSDF and its relevance for biological systems.

Dissociation of iodine molecules and singlet oxygen generation in O2 - I2 mixture induced by 1315-nm laser radiation

NASA Astrophysics Data System (ADS)

Zagidullin, M. V.; Khvatov, N. A.; Malyshev, M. S.; Azyazov, V. N.

2017-11-01

It is observed that laser light at a wavelength of 1315 nm induces continuous stable fluorescence at the O2(b1Σ → X3Σ) and I2(B3Πu → X1Σ) bands in a O2 - I2 mixture preliminarily irradiated at a wavelength of 532 nm to achieve partial photolysis of iodine molecules. This testifies to generation of iodine atoms and excited O2(a1Δ), O2(b1Σ), and I2(B3Πu) molecules in the O2 - I2 mixture under irradiation at 1315 nm.

Quantum Dot-Based Luminescent Oxygen Channeling Assay for Potential Application in Homogeneous Bioassays.

PubMed

Zhuang, Si-Hui; Guo, Xin-Xin; Wu, Ying-Song; Chen, Zhen-Hua; Chen, Yao; Ren, Zhi-Qi; Liu, Tian-Cai

2016-01-01

The unique photoproperties of quantum dots are promising for potential application in bioassays. In the present study, quantum dots were applied to a luminescent oxygen channeling assay. The reaction system developed in this study was based on interaction of biotin with streptavidin. Carboxyl-modified polystyrene microspheres doped with quantum dots were biotinylated and used as acceptors. Photosensitizer-doped carboxyl-modified polystyrene microspheres were conjugated with streptavidin and used as donors. The results indicated that the singlet oxygen that was released from the donor beads diffused into the acceptor beads. The acceptor beads were then exited via thioxene, and were subsequently fluoresced. To avoid generating false positives, a high concentration (0.01 mg/mL) of quantum dots is required for application in homogeneous immunoassays. Compared to a conventional luminescent oxygen channeling assay, this quantum dots-based technique requires less time, and would be easier to automate and miniaturize because it requires no washing to remove excess labels.

Mechanisms of group A Streptococcus resistance to reactive oxygen species

PubMed Central

Henningham, Anna; Döhrmann, Simon; Nizet, Victor; Cole, Jason N.

2015-01-01

Streptococcus pyogenes, also known as group A Streptococcus (GAS), is an exclusively human Gram-positive bacterial pathogen ranked among the ‘top 10’ causes of infection-related deaths worldwide. GAS commonly causes benign and self-limiting epithelial infections (pharyngitis and impetigo), and less frequent severe invasive diseases (bacteremia, toxic shock syndrome and necrotizing fasciitis). Annually, GAS causes 700 million infections, including 1.8 million invasive infections with a mortality rate of 25%. In order to establish an infection, GAS must counteract the oxidative stress conditions generated by the release of reactive oxygen species (ROS) at the infection site by host immune cells such as neutrophils and monocytes. ROS are the highly reactive and toxic byproducts of oxygen metabolism, including hydrogen peroxide (H2O2), superoxide anion (O2•−), hydroxyl radicals (OH•) and singlet oxygen (O2*), which can damage bacterial nucleic acids, proteins and cell membranes. This review summarizes the enzymatic and regulatory mechanisms utilized by GAS to thwart ROS and survive under conditions of oxidative stress. PMID:25670736

Mechanisms of group A Streptococcus resistance to reactive oxygen species.

PubMed

Henningham, Anna; Döhrmann, Simon; Nizet, Victor; Cole, Jason N

2015-07-01

Streptococcus pyogenes, also known as group A Streptococcus (GAS), is an exclusively human Gram-positive bacterial pathogen ranked among the 'top 10' causes of infection-related deaths worldwide. GAS commonly causes benign and self-limiting epithelial infections (pharyngitis and impetigo), and less frequent severe invasive diseases (bacteremia, toxic shock syndrome and necrotizing fasciitis). Annually, GAS causes 700 million infections, including 1.8 million invasive infections with a mortality rate of 25%. In order to establish an infection, GAS must counteract the oxidative stress conditions generated by the release of reactive oxygen species (ROS) at the infection site by host immune cells such as neutrophils and monocytes. ROS are the highly reactive and toxic byproducts of oxygen metabolism, including hydrogen peroxide (H2O2), superoxide anion (O2•(-)), hydroxyl radicals (OH•) and singlet oxygen (O2*), which can damage bacterial nucleic acids, proteins and cell membranes. This review summarizes the enzymatic and regulatory mechanisms utilized by GAS to thwart ROS and survive under conditions of oxidative stress. © FEMS 2015.

NEW APPROACHES TO ESTIMATING INDIRECT PHOTOLYSIS RATES IN AQUATIC ENVIRONMENTS

EPA Science Inventory

Indirect photoreactions in aquatic environments are driven by reactive species, most of which are oxygen centered. Humic substances play an important role in photosensitizing the production of these reactive species, which include singlet molecular oxygen, superoxide ions, hydrog...

Effects of molecular packing in organic crystals on singlet fission with ab initio many body perturbation theory

NASA Astrophysics Data System (ADS)

Haber, Jonah; Refaely-Abramson, Sivan; da Jornada, Felipe H.; Louie, Steven G.; Neaton, Jeffrey B.

Multi-exciton generation processes, in which multiple charge carriers are generated from a single photon, are mechanisms of significant interest for achieving efficiencies beyond the Shockley-Queisser limit of conventional p-n junction solar cells. One well-studied multiexciton process is singlet fission, whereby a singlet decays into two spin-correlated triplet excitons. Here, we use a newly developed computational approach to calculate singlet-fission coupling terms and rates with an ab initio Green's function formalism based on many-body perturbation theory (MBPT) within the GW approximation and the Bethe-Salpeter equation approach. We compare results for crystalline pentacene and TIPS-pentacene and explore the effect of molecular packing on the singlet fission mechanism. This work is supported by the Department of Energy.

Generation of reactive oxygen species and charge carriers in plasmonic photocatalytic Au@TiO2 nanostructures with enhanced activity.

PubMed

He, Weiwei; Cai, Junhui; Jiang, Xiumei; Yin, Jun-Jie; Meng, Qingbo

2018-06-13

The combination of semiconductor and plasmonic nanostructures, endowed with high efficiency light harvesting and surface plasmon confinement, has been a promising way for efficient utilization of solar energy. Although the surface plasmon resonance (SPR) assisted photocatalysis has been extensively studied, the photochemical mechanism, e.g. the effect of SPR on the generation of reactive oxygen species and charge carriers, is not well understood. In this study, we take Au@TiO2 nanostructures as a plasmonic photocatalyst to address this critical issue. The Au@TiO2 core/shell nanostructures with tunable SPR property were synthesized by the templating method with post annealing thermal treatment. It was found that Au@TiO2 nanostructures exhibit enhanced photocatalytic activity in either sunlight or visible light (λ > 420 nm). Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au@TiO2 on the photo-induced reactive oxygen species and charge carriers. The formation of Au@TiO2 core/shell nanostructures resulted in a dramatic increase in light-induced generation of hydroxyl radicals, singlet oxygen, holes and electrons, as compared with TiO2 alone. This enhancement under visible light (λ > 420 nm) irradiation may be dominated by SPR induced local electrical field enhancement, while the enhancement under sunlight irradiation is dominated by the higher electron transfer from TiO2 to Au. These results unveiled that the superior photocatalytic activity of Au@TiO2 nanostructures correlates with enhanced generation of reactive oxygen species and charge carriers.

A theoretical study of a series of water-soluble triphenylamine photosensitizers for two-photon photodynamic therapy.

PubMed

Wang, Xin; Yin, Xue; Lai, Xiao-Yong; Liu, Ying-Tao

2018-10-05

In this study, the therapeutic activity of a series of water-soluble triphenylamine (TP) photosensitizers (Ps) was explored by using theoretical simulations. The key photophysical parameters which determined the efficiency of Ps, such as absorption electronic spectra, singlet-triplet energy gaps and spin-orbit matrix elements were calculated at density functional theory and its time-dependent extension (DFT, TD-DFT). The calculated results showed that these TP photosensitizers possessed large two-photon absorption cross-section in the near-infrared region (NIR), efficient intersystem crossing (ISC) transition from the first singlet excited state to the low lying triplet excited states and sufficient energy for generating reactive oxygen species (ROS). These suitable features made these TP series holding great promise for applications in two-photon photodynamic therapy (PDT). These TP photosensitizers studied here in principle extended the application range of two-photon PDT in water solution. Copyright © 2018 Elsevier B.V. All rights reserved.

A Highly Efficient and Photostable Photosensitizer with Near-Infrared Aggregation-Induced Emission for Image-Guided Photodynamic Anticancer Therapy.

PubMed

Wu, Wenbo; Mao, Duo; Hu, Fang; Xu, Shidang; Chen, Chao; Zhang, Chong-Jing; Cheng, Xiamin; Yuan, Youyong; Ding, Dan; Kong, Deling; Liu, Bin

2017-09-01

Photodynamic therapy (PDT), which relies on photosensitizers (PS) and light to generate reactive oxygen species to kill cancer cells or bacteria, has attracted much attention in recent years. PSs with both bright emission and efficient singlet oxygen generation have also been used for image-guided PDT. However, simultaneously achieving effective 1 O 2 generation, long wavelength absorption, and stable near-infrared (NIR) emission with low dark toxicity in a single PS remains challenging. In addition, it is well known that when traditional PSs are made into nanoparticles, they encounter quenched fluorescence and reduced 1 O 2 production. In this contribution, these challenging issues have been successfully addressed through designing the first photostable photosensitizer with aggregation-induced NIR emission and very effective 1 O 2 generation in aggregate state. The yielded nanoparticles show very effective 1 O 2 generation, bright NIR fluorescence centered at 820 nm, excellent photostability, good biocompatibility, and negligible dark in vivo toxicity. Both in vitro and in vivo experiments prove that the nanoparticles are excellent candidates for image-guided photodynamic anticancer therapy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of Direct and Indirect Photolysis in Imazosulfuron Photodegradation.

PubMed

Rering, Caitlin; Williams, Katryn; Hengel, Matt; Tjeerdema, Ronald

2017-04-19

Imazosulfuron, a sulfonylurea herbicide used in rice cultivation, has been shown to undergo photodegradation in water, but neither the photochemical mechanism nor the role of indirect photolysis is known. The purpose of this study was to investigate the underlying processes that operate on imazosulfuron during aqueous photodegradation. Our data indicate that in the presence of oxygen, most photochemical degradation proceeds through a direct singlet-excited state pathway, whereas triplet-excited state imazosulfuron enhanced decay rates under low dissolved oxygen conditions. Oxidation by hydroxyl radical and singlet oxygen were not significant. At dissolved organic matter (DOM) concentrations representative of rice field conditions, fulvic acid solutions exhibited faster degradation than rice field water containing both humic and fulvic acid fractions. Both enhancement, via reaction with triplet-state DOM, and inhibition, via competition for photons, of degradation was observed in DOM solutions.

Stereoselectivity in ene reactions with 1O2: matrix effects in polymer supports, photo-oxygenation of organic salts and asymmetric synthesis.

PubMed

Griesbeck, Axel G; Bartoschek, Anna; Neudörfl, Jörg; Miara, Claus

2006-01-01

The ene reaction of chiral allylic alcohols is applied as a tool for the investigation of intrapolymer effects by means of the stereoselectivity of the singlet-oxygen addition. The diastereo selectivity strongly depends on the structure of the polymer, the substrate loading degree and also on the degree of conversion demonstrating additional supramolecular effects evolving during the reaction. The efficiency and the stability of polymer-bound sensitizers were evaluated by the ene reaction of singlet oxygen with citronellol. The ene reaction with chiral ammonium salts of tiglic acid was conducted under solution phase conditions or in polystyrene beads under chiral contact ion-pair conditions. The products thus obtained precipitate during the photoreaction as ammonium salts. Moderate asymmetric induction was observed for this procedure for the first time.

The Three Forms of Molecular Oxygen.

ERIC Educational Resources Information Center

Laing, Michael

1989-01-01

Finds that a logical application of the simple rules of the molecular orbital bonding theory for diatomic molecules predicted the existence of three spin isomers of the oxygen molecule: one triplet form with two unpaired electrons and two singlet forms with all electrons paired. (MVL)

ROS Mediated Stress Response in Illuminated Cattle Feces Derived DOM

EPA Science Inventory

Bacterial exposure to exogenous reactive oxygen species (ROS) is known to increase theexpression of oxidative stress related genes and has been linked to acquisition of antibioticresistance (AR). ROS, including hydrogen peroxide (H202), singlet oxygen e o 2), andhydroxyl radicals...

Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms

NASA Astrophysics Data System (ADS)

Giacomazzi, Luigi; Martin-Samos, L.; Boukenter, A.; Ouerdane, Y.; Girard, S.; Alessi, A.; de Gironcoli, S.; Richard, N.

2017-05-01

In this work we present an extensive investigation of nanoscale physical phenomena related to oxygen-deficient centers (ODCs) in silica and Ge-doped silica by means of first-principles calculations, including nudged-elastic band, electron paramagnetic resonance parameters calculations, and many-body perturbation theory (GW and Bethe-Salpeter equation) techniques. We show that by neutralizing positively charged oxygen monovacancies we can obtain model structures of twofold Si and Ge defects of which the calculated absorption spectra and singlet-to-triplet transitions are in excellent agreement with the experimental optical absorption and photo-luminescence data. In particular we provide an exhaustive analysis of the main exciton peaks related to the presence of twofold defects including long-range correlation effects. By calculating the reaction pathways and energy barriers necessary for the interconversion, we advance a double precursory origin of the {E}α \\prime and Ge(2) centers as due to the ionization of neutral oxygen monovacancies (Si-Si and Ge-Si dimers) and as due to the ionization of twofold Si and Ge defects. Furthermore two distinct structural conversion mechanisms are found to occur between the neutral oxygen monovacancy and the twofold Si (and Ge) atom configurations. Such conversion mechanisms allow to explain the radiation induced generation of the ODC(II) centers, their photobleaching, and also their generation during the drawing of optical fibers.

Green synthesis of carbon quantum dots embedded onto titanium dioxide nanowires for enhancing photocurrent

NASA Astrophysics Data System (ADS)

Yen, Yin-Cheng; Lin, Chia-Chi; Chen, Ping-Yu; Ko, Wen-Yin; Tien, Tzu-Rung; Lin, Kuan-Jiuh

2017-05-01

The green synthesis of nanowired photocatalyst composed of carbon quantum dots-titanium hybrid-semiconductors, CQDs/TiO2, are reported. Where graphite-based CQDs with a size less than 5 nm are directly synthesized in pure water electrolyte by a one-step electrochemistry approach and subsequently electrodeposited onto as-prepared TiO2 nanowires through a voltage-driven reduction process. Electron paramagnetic resonance studies show that the CQDs can generate singlet oxygen and/or oxygen radicals to decompose the kinetic H2O2 intermediate species upon UV light illumination. With the effect of peroxidase-like CQDs, photocurrent density of CQDs/TiO2 is remarkably enhanced by a 6.4 factor when compared with that of as-prepared TiO2.

Impact of Photosensitizers Activation on Intracellular Trafficking and Viscosity

PubMed Central

Aubertin, Kelly; Bonneau, Stéphanie; Silva, Amanda K. A.; Bacri, Jean-Claude; Gallet, François; Wilhelm, Claire

2013-01-01

The intracellular microenvironment is essential for the efficiency of photo-induced therapies, as short-lived reactive oxygen species generated must diffuse through their intracellular surrounding medium to reach their cellular target. Here, by combining measurements of local cytoplasmic dissipation and active trafficking, we found that photosensitizers activation induced small changes in surrounding viscosity but a massive decrease in diffusion. These effects are the signature of a return to thermodynamic equilibrium of the system after photo-activation and correlated with depolymerization of the microtubule network, as shown in a reconstituted system. These mechanical measurements were performed with two intracellular photosensitizing chlorins having similar quantum yield of singlet oxygen production but different intracellular localizations (cytoplasmic for mTHPC, endosomal for TPCS2a). These two agents demonstrated different intracellular impact. PMID:24386423

Explicit macroscopic singlet oxygen modeling for benzoporphyrin derivative monoacid ring A (BPD)-mediated photodynamic therapy.

PubMed

Kim, Michele M; Penjweini, Rozhin; Liang, Xing; Zhu, Timothy C

2016-11-01

Photodynamic therapy (PDT) is an effective non-ionizing treatment modality that is currently being used for various malignant and non-malignant diseases. In type II PDT with photosensitizers such as benzoporphyrin monoacid ring A (BPD), cell death is based on the creation of singlet oxygen ( 1 O 2 ). With a previously proposed empirical five-parameter macroscopic model, the threshold dose of singlet oxygen ([ 1 O 2 ] rx,sh ]) to cause tissue necrosis in tumors treated with PDT was determined along with a range of the magnitude of the relevant photochemical parameters: the photochemical oxygen consumption rate per light fluence rate and photosensitizer concentration (ξ), the probability ratio of 1 O 2 to react with ground state photosensitizer compared to a cellular target (σ), the ratio of the monomolecular decay rate of the triplet state photosensitizer (β), the low photosensitizer concentration correction factor (δ), and the macroscopic maximum oxygen supply rate (g). Mice bearing radiation-induced fibrosarcoma (RIF) tumors were treated interstitially with a linear light source at 690nm with total energy released per unit length of 22.5-135J/cm and source power per unit length of 12-150mW/cm to induce different radii of necrosis. A fitting algorithm was developed to determine the photochemical parameters by minimizing the error function involving the range between the calculated reacted singlet oxygen ([ 1 O 2 ] rx ) at necrosis radius and the [ 1 O 2 ] rx,sh . [ 1 O 2 ] rx was calculated based on explicit dosimetry of the light fluence distribution, the tissue optical properties, and the BPD concentration. The initial ground state oxygen concentration ([ 3 O 2 ] 0 ) was set to be 40μM in this study. The photochemical parameters were found to be ξ=(55±40)×10 -3 cm 2 mW -1 s -1 , σ=(1.8±3)×10 -5 μM -1 , and g=1.7±0.7μMs -1 . We have taken the literature values for δ=33μM, and β=11.9μM. [ 1 O 2 ] rx has shown promise to be a more effective dosimetry quantity for predicting necrosis than either light dose or PDT dose, where the latter is simplistically a temporal integral of the products of the photosensitizer concentration and light fluence rate. Copyright © 2016 Elsevier B.V. All rights reserved.

Monitoring and assessment of tumor hemodynamics during pleural PDT

NASA Astrophysics Data System (ADS)

Ong, Yi Hong; Kim, Michele M.; Penjweini, Rozhin; Rodriguez, Carmen E.; Dimofte, Andrea; Finlay, Jarod C.; Busch, Theresa M.; Yodh, Arjun G.; Cengel, Keith A.; Singhal, Sunil; Zhu, Timothy C.

2017-02-01

Intrapleural photodynamic therapy (PDT) has been used in combination with lung sparing surgery to treat patients with malignant pleural mesothelioma. The light, photosensitizers and tissue oxygen are the three most important factors required by type II PDT to produce singlet oxygen, 1O2, which is the main photocytotoxic agent that damages the tumor vasculature and stimulates the body's anti-tumor immune response. Although light fluence rate and photosensitizer concentrations are routinely monitored during clinical PDT, there is so far a lack of a Food and Drug Administration (FDA)-approved non-invasive technique that can be employed clinically to monitor tissue oxygen in vivo. In this paper, we demonstrated that blood flow correlates well with tissue oxygen concentration during PDT and can be used in place of [3O2] to calculate reacted singlet oxygen concentration [1O2]rx using the macroscopic singlet oxygen model. Diffuse correlation spectroscopy (DCS) was used to monitor the change in tissue blood flow non-invasively during pleural PDT. A contact probe with three source and detectors separations, 0.4, 0.7 and 1.0-cm, was sutured to the pleural cavity wall of the patients after surgical resection of the pleural mesothelioma tumor to monitor the tissue blood flow during intraoperative PDT treatment. The changes of blood flow during PDT of 2 patients are found to be in good correlation with the treatment light fluence rate recorded by the isotropic detector placed adjacent to the DCS probe. [1O2]rx calculated based on light fluence, mean photosensitizer concentration, and relative blood flow was found to be 32% higher in patient #4 (0.50mM) than that for patient #3 (0.38mM).

Luminescence of the (O2(a(1)Δ(g)))2 collisional complex in the temperature range of 90-315 K: Experiment and theory.

PubMed

Zagidullin, M V; Pershin, A A; Azyazov, V N; Mebel, A M

2015-12-28

Experimental and theoretical studies of collision induced emission of singlet oxygen molecules O2(a(1)Δg) in the visible range have been performed. The rate constants, half-widths, and position of peaks for the emission bands of the (O2(a(1)Δg))2 collisional complex centered around 634 nm (2) and 703 nm (3) have been measured in the temperature range of 90-315 K using a flow-tube apparatus that utilized a gas-liquid chemical singlet oxygen generator. The absolute values of the spontaneous emission rate constants k2 and k3 are found to be similar, with the k3/k2 ratio monotonically decreasing from 1.1 at 300 K to 0.96 at 90 K. k2 slowly decreases with decreasing temperature but a sharp increase in its values is measured below 100 K. The experimental results were rationalized in terms of ab initio calculations of the ground and excited potential energy and transition dipole moment surfaces of singlet electronic states of the (O2)2 dimole, which were utilized to compute rate constants k2 and k3 within a statistical model. The best theoretical results reproduced experimental rate constants with the accuracy of under 40% and correctly described the observed temperature dependence. The main contribution to emission process (2), which does not involve vibrational excitation of O2 molecules at the ground electronic level, comes from the spin- and symmetry-allowed 1(1)Ag←(1)B3u transition in the rectangular H configuration of the dimole. Alternatively, emission process (3), in which one of the monomers becomes vibrationally excited in the ground electronic state, is found to be predominantly due to the vibronically allowed 1(1)Ag←2(1)Ag transition induced by the asymmetric O-O stretch vibration in the collisional complex. The strong vibronic coupling between nearly degenerate excited singlet states of the dimole makes the intensities of vibronically and symmetry-allowed transitions comparable and hence the rate constants k2 and k3 close to one another.

Singlet oxygen Triplet Energy Transfer based imaging technology for mapping protein-protein proximity in intact cells

PubMed Central

To, Tsz-Leung; Fadul, Michael J.; Shu, Xiaokun

2014-01-01

Many cellular processes are carried out by large protein complexes that can span several tens of nanometers. Whereas Forster resonance energy transfer has a detection range of <10 nm, here we report the theoretical development and experimental demonstration of a new fluorescence imaging technology with a detection range of up to several tens of nanometers: singlet oxygen triplet energy transfer. We demonstrate that our method confirms the topology of a large protein complex in intact cells, which spans from the endoplasmic reticulum to the outer mitochondrial membrane and the matrix. This new method is thus suited for mapping protein proximity in large protein complexes. PMID:24905026

Solar photolysis of ozone to singlet D oxygen atoms

NASA Technical Reports Server (NTRS)

Blackburn, Thomas E.; Bairai, Solomon T.; Stedman, Donald H.

1992-01-01

The ground-level photolysis frequency of ozone J(O3) to produce metastable singlet D oxygen atoms (O (D-1)) is measured using a novel instrumental technique involving electrical conductivity. The O(D-1) atoms produced react with nitrous oxide (N2O) carrier gas to form higher oxides of nitrogen (NO(x)). These oxides were detected by mixing with methanol and determining the increase in electrical conductivity with a continuous-flow dual conductivity cell. Over 70 days of data were collected under varying sky conditions. The effect of temperature on J(O3) was measured. The results agree with model predictions. The effects of atmospheric aerosols, changes in overhead ozone column, and local cloudiness are discussed.

Deciphering early events involved in hyperosmotic stress-induced programmed cell death in tobacco BY-2 cells

PubMed Central

Monetti, Emanuela; Kadono, Takashi; Bouteau, François

2014-01-01

Hyperosmotic stresses represent one of the major constraints that adversely affect plants growth, development, and productivity. In this study, the focus was on early responses to hyperosmotic stress- (NaCl and sorbitol) induced reactive oxygen species (ROS) generation, cytosolic Ca2+ concentration ([Ca2+]cyt) increase, ion fluxes, and mitochondrial potential variations, and on their links in pathways leading to programmed cell death (PCD). By using BY-2 tobacco cells, it was shown that both NaCl- and sorbitol-induced PCD seemed to be dependent on superoxide anion (O2·–) generation by NADPH-oxidase. In the case of NaCl, an early influx of sodium through non-selective cation channels participates in the development of PCD through mitochondrial dysfunction and NADPH-oxidase-dependent O2·– generation. This supports the hypothesis of different pathways in NaCl- and sorbitol-induced cell death. Surprisingly, other shared early responses, such as [Ca2+]cyt increase and singlet oxygen production, do not seem to be involved in PCD. PMID:24420571

Light-Induced Transformations of the C60 Derivative, Fullerenol: Interactions with Natural Organic Matter

EPA Science Inventory

Recent studies have indicated that fullerenes, an important class of nanomaterials, are photodegraded by solar radiation and can sensitize the photoproduction of reactive oxygen species such as singlet oxygen. Because natural organic matter (NOM) can retard photoreactions that a...

Systemic reduction of rice blast by means of photosensitizers

USDA-ARS?s Scientific Manuscript database

Acquired disease resistance of plants may be induced by exogenous reactive oxygen species or their sources. Certain compounds (photosensitizers) produce ROS at the expense of light energy. This study used photodynamic dyes bengal rose and methylene blue, which yield singlet oxygen, and mercaptopyrid...

Oxygen sensing with an absolute optical sensor based on biluminescence (Conference Presentation)

NASA Astrophysics Data System (ADS)

Salas Redondo, Caterin; Reineke, Sebastian

2017-06-01

Organic semiconductors are materials having the benefits of semiconductors together with those of organic molecules. That means, on one hand, these are compounds able to absorb and emit light, as well as conduct electricity to a certain extent, which is enough for the functionality of solid state devices. On the other hand, a remarkable characteristic is that the excitations are typically localized on individual molecules, such that the exchange interactions lead to energetically distinct singlet and triplet states. According to the spectroscopic selection rules in quantum mechanics, only transitions from the singlet excited state are allowed, deactivating radiatively while generating fluorescence emission in the process, whereas transitions from the triplet excited state are not allowed, because its decay involves a spin flip, and therefore, it is theoretically forbidden by electric dipole transitions. Nevertheless, there is a small probability of these forbidden transitions to occur at a low rate, resulting in a slow radiative deactivation known as phosphorescence emission. In this context, the property of an organic molecule able to emit light from both their singlet and triplet excited states is called biluminescence. Although this dual state emission, particularly at room temperature, is difficult to achieve by purely organic molecules, it becomes possible if competitive thermal decay is suppressed effectively, allowing emission from the triplet states (i.e. phosphorescence) in addition to the conventional fluorescence. Here, we have identified biluminescence in simple host:guest systems in which a biluminophore (i.e. organic molecule with biluminescence property) is embedded in an optimum rigid matrix, for example, a combination of PMMA [poly(methyl methacrylate)] as host and NPB [N,N'-di(naphtha-1-yl)-N,N'-diphenyl-benzidine] as biluminophore [Reineke and Baldo, Sci. Rep.]. Such system is unique not only because of the dual state emission, but also the large exciton dynamic range extended up to nine orders of magnitude between nanosecond-lifetime fluorescence and millisecond-lifetime phosphorescence. In this presentation, we will report on the oxygen sensing characteristics of this luminescent system compared to a benchmarked single state optical sensor. Such properties can be evaluated because of the sensitivity of the triplet state to oxygen and therefore, we investigate the dependence of the persistent phosphorescence on the oxygen content. Furthermore, we will address our efforts towards the potential integration of novel optical biluminescent sensing into organic electronics.

Poly(D, L-lactide-co-glycolide) nanoparticles as delivery agents for photodynamic therapy: enhancing singlet oxygen release and photototoxicity by surface PEG coating

NASA Astrophysics Data System (ADS)

Boix-Garriga, Ester; Acedo, Pilar; Casadó, Ana; Villanueva, Angeles; Stockert, Juan Carlos; Cañete, Magdalena; Mora, Margarita; Lluïsa Sagristá, Maria; Nonell, Santi

2015-09-01

Poly(D, L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) are being considered as nanodelivery systems for photodynamic therapy. The physico-chemical and biological aspects of their use remain largely unknown. Herein we report the results of a study of PLGA NPs for the delivery of the model hydrophobic photosensitizer ZnTPP to HeLa cells. ZnTPP was encapsulated in PLGA with high efficiency and the NPs showed negative zeta potentials and diameters close to 110 nm. Poly(ethylene glycol) (PEG) coating, introduced to prevent opsonization and clearance by macrophages, decreased the size and zeta potential of the NPs by roughly a factor of two and improved their stability in the presence of serum proteins. Photophysical studies revealed two and three populations of ZnTPP and singlet oxygen in uncoated and PEGylated NPs, respectively. Singlet oxygen is confined within the NPs in bare PLGA while it is more easily released into the external medium after PEG coating, which contributes to a higher photocytotoxicity towards HeLa cells in vitro. PLGA NPs are internalized by endocytosis, deliver their cargo to lysosomes and induce cell death by apoptosis upon exposure to light. In conclusion, PLGA NPs coated with PEG show high potential as delivery systems for photodynamic applications.

Indocyanine green-loaded hollow mesoporous silica nanoparticles as an activatable theranostic agent

NASA Astrophysics Data System (ADS)

Hong, Suk ho; Kim, Hyunjin; Choi, Yongdoo

2017-05-01

Here we report indocyanine green (ICG)-loaded hollow mesoporous silica nanoparticles (ICG@HMSNP) as an activatable theranostic platform. Near-infrared fluorescence and singlet oxygen generation of ICG@HMSNP was effectively quenched (i.e. turned off) in its native state because of the fluorescence resonance energy transfer between ICG molecules. Therefore, ICG@HMSNP was nonfluorescent and nonphototoxic in the extracellular region. After the nanoparticles entered the cancer cells via endocytosis, they became highly fluorescent and phototoxic. In addition, intracellular uptake of ICG@HMSNP was 2.75 times higher than that of free ICG, resulting in an enhanced phototherapy of cancer.

Virus-Based Cancer Therapeutics for Targeted Photodynamic Therapy.

PubMed

Cao, Binrui; Xu, Hong; Yang, Mingying; Mao, Chuanbin

2018-01-01

Cancer photodynamic therapy (PDT) involves the absorption of light by photosensitizers (PSs) to generate cytotoxic singlet oxygen for killing cancer cells. The success of this method is usually limited by the lack of selective accumulation of the PS at cancer cells. Bioengineered viruses with cancer cell-targeting peptides fused on their surfaces are great drug carriers that can guide the PS to cancer cells for targeted cancer treatment. Here, we use cell-targeting fd bacteriophages (phages) as an example to describe how to chemically conjugate PSs (e.g., pyropheophorbide-a (PPa)) onto a phage particle to achieve targeted PDT.

Oxidation-Induced Increase In Photoreactivity of Bovine Retinal Lipid Extract.

PubMed

Koscielniak, A; Serafin, M; Duda, M; Oles, T; Zadlo, A; Broniec, A; Berdeaux, O; Gregoire, S; Bretillon, L; Sarna, T; Pawlak, A

2017-12-01

The mammalian retina contains a high level of polyunsaturated fatty acids, including docosahexaenoic acid (22:6) (DHA), which are highly susceptible to oxidation. It has been shown that one of the products of DHA oxidation-carboxyethylpyrrole (CEP), generated in situ, causes modifications of retinal proteins and induces inflammation response in the outer retina. These contributing factors may play a role in the development of age-related macular degeneration (AMD). It is also possible that some of the lipid oxidation products are photoreactive, and upon irradiation with blue light may generate reactive oxygen species. Therefore, in this work we analysed oxidation-induced changes in photoreactivity of lipids extracted from bovine neural retinas. Lipid composition of bovine neural retinas closely resembles that of human retinas making the bovine tissue a convenient model for studying the photoreactivity and potential phototoxicity of oxidized human retinal lipids. Lipid composition of bovine neural retinas Folch' extracts (BRex) was determined by gas chromatography (GC) and liquid chromatography coupled to an electrospray ionization source-mass spectrometer (LC-ESI-MS) analysis. Liposomes prepared from BRex, equilibrated with air, were oxidized in the dark at 37 °C for up to 400 h. The photoreactivity of BRex at different stages of oxidation was studied by EPR-oximetry and EPR-spin trapping. Photogeneration of singlet oxygen ( 1 O 2 , 1 Δ g ) by BRex was measured using time-resolved detection of the characteristic phosphorescence at 1270 nm. To establish contribution of lipid components to the analysed photoreactivity of Folch' extract of bovine retinas, a mixture of selected synthetic lipids in percent by weight (w/w %) ratio resembling that of the BRex has been also studied. Folch's extraction of bovine neural retinas was very susceptible to oxidation despite the presence of powerful endogenous antioxidants such as α-tocopherol and zeaxanthin. Non-oxidized and oxidized BRex photogenerated singlet oxygen with moderate quantum yield. Blue-light induced generation of superoxide anion by Folch' extract of bovine neural retinas strongly depended on the oxidation time. The observed photoreactivity of the studied extract gradually increased during its in vitro oxidation.

Singlet oxygen and ROS in a new light: low-dose subcellular photodynamic treatment enhances proliferation at the single cell level.

PubMed

Blázquez-Castro, Alfonso; Breitenbach, Thomas; Ogilby, Peter R

2014-09-01

Two-photon excitation of a sensitizer with a focused laser beam was used to create a spatially-localized subcellular population of reactive oxygen species, ROS, in single HeLa cells. The sensitizer used was protoporphyrin IX, PpIX, endogenously derived from 5-aminolevulinic acid delivered to the cells. Although we infer that singlet oxygen, O2(a(1)Δg), is one ROS produced upon irradiation of PpIX under these conditions, it is possible that the superoxide ion, O2(-˙), may also play a role in this system. With a "high" dose of PpIX-sensitized ROS, the expected death of the cell was observed. However, under "low dose" conditions, clear signs of cell proliferation were observed. The present results facilitate studies of ROS-mediated signalling in imaging-based single cell experiments.

Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen.

PubMed

Ushakov, Dmitry B; Gilmore, Kerry; Kopetzki, Daniel; McQuade, D Tyler; Seeberger, Peter H

2014-01-07

Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitroxide free radicals protect macular carotenoids against chemical destruction (bleaching) during lipid peroxidation

PubMed Central

Zareba, M.; Widomska, J.; Burke, J. M.; Subczynski, W. K.

2016-01-01

Macular xanthophylls (MXs) lutein and zeaxanthin are dietary carotenoids that are selectively concentrated in the human eye retina, where they are thought to protect against age-related macular degeneration (AMD) by multiple mechanisms, including filtration of phototoxic blue light and quenching of singlet oxygen and triplet states of photosensitizers. These physical protective mechanisms require that MXs be in their intact structure. Here, we investigated the protection of the intact structure of zeaxanthin incorporated into model membranes subjected to oxidative modification by water- and/or membrane-soluble small nitroxide free radicals. Model membranes were formed from saturated, monounsaturated, and polyunsaturated phosphatidylcholines (PCs). Oxidative modification involved autoxidation, iron-mediated, and singlet oxygen-mediated lipid peroxidation. The extent of chemical destruction (bleaching) of zeaxanthin was evaluated from its absorption spectra and compared with the extent of lipid peroxidation evaluated using the thiobarbituric acid assay. Nitroxide free radicals with different polarity (membrane/water partition coefficients) were used. The extent of zeaxanthin bleaching increased with membrane unsaturation and correlated with the rate of PC oxidation. Protection of the intact structure of zeaxanthin by membrane-soluble nitroxides was much stronger than that by water-soluble nitroxides. The combination of zeaxanthin and lipid-soluble nitroxides exerted strong synergistic protection against singlet oxygen-induced lipid peroxidation. The synergistic effect may be explained in terms of protection of the intact zeaxanthin structure by effective scavenging of free radicals by nitroxides, therefore allowing zeaxanthin to quench the primary oxidant, singlet oxygen, effectively by the physical protective mechanism. The redox state of nitroxides was monitored using electron paramagnetic resonance spectroscopy. Both nitroxide free radicals and their reduced form, hydroxylamines, were equally effective. Obtained data were compared with the protective effects of α-tocopherol, which is the natural antioxidant and protector of MXs within the retina. The new strategies employed here to maintain the intact structure of MXs may enhance their protective potential against AMD. PMID:27840316

Nitroxide free radicals protect macular carotenoids against chemical destruction (bleaching) during lipid peroxidation.

PubMed

Zareba, M; Widomska, J; Burke, J M; Subczynski, W K

2016-12-01

Macular xanthophylls (MXs) lutein and zeaxanthin are dietary carotenoids that are selectively concentrated in the human eye retina, where they are thought to protect against age-related macular degeneration (AMD) by multiple mechanisms, including filtration of phototoxic blue light and quenching of singlet oxygen and triplet states of photosensitizers. These physical protective mechanisms require that MXs be in their intact structure. Here, we investigated the protection of the intact structure of zeaxanthin incorporated into model membranes subjected to oxidative modification by water- and/or membrane-soluble small nitroxide free radicals. Model membranes were formed from saturated, monounsaturated, and polyunsaturated phosphatidylcholines (PCs). Oxidative modification involved autoxidation, iron-mediated, and singlet oxygen-mediated lipid peroxidation. The extent of chemical destruction (bleaching) of zeaxanthin was evaluated from its absorption spectra and compared with the extent of lipid peroxidation evaluated using the thiobarbituric acid assay. Nitroxide free radicals with different polarity (membrane/water partition coefficients) were used. The extent of zeaxanthin bleaching increased with membrane unsaturation and correlated with the rate of PC oxidation. Protection of the intact structure of zeaxanthin by membrane-soluble nitroxides was much stronger than that by water-soluble nitroxides. The combination of zeaxanthin and lipid-soluble nitroxides exerted strong synergistic protection against singlet oxygen-induced lipid peroxidation. The synergistic effect may be explained in terms of protection of the intact zeaxanthin structure by effective scavenging of free radicals by nitroxides, therefore allowing zeaxanthin to quench the primary oxidant, singlet oxygen, effectively by the physical protective mechanism. The redox state of nitroxides was monitored using electron paramagnetic resonance spectroscopy. Both nitroxide free radicals and their reduced form, hydroxylamines, were equally effective. Obtained data were compared with the protective effects of α-tocopherol, which is the natural antioxidant and protector of MXs within the retina. The new strategies employed here to maintain the intact structure of MXs may enhance their protective potential against AMD. Copyright © 2016 Elsevier Inc. All rights reserved.

Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication

PubMed Central

Graindorge, Dany; Martineau, Sylvain; Machon, Christelle; Arnoux, Philippe; Guitton, Jérôme; Francesconi, Stefania; Frochot, Céline; Sage, Evelyne; Girard, Pierre-Marie

2015-01-01

UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen. PMID:26485711

Gold nanoshells-mediated bimodal photodynamic and photothermal cancer treatment using ultra-low doses of near infra-red light.

PubMed

Vankayala, Raviraj; Lin, Chun-Chih; Kalluru, Poliraju; Chiang, Chi-Shiun; Hwang, Kuo Chu

2014-07-01

Previously, gold nanoshells were shown to be able to effectively convert photon energy to heat, leading to hyperthermia and suppression of tumor growths in mice. Herein, we show that in addition to the nanomaterial-mediated photothermal effects (NmPTT), gold nanoshells (including, nanocages, nanorod-in-shell and nanoparticle-in-shell) not only are able to absorb NIR light, but can also emit fluorescence, sensitize formation of singlet oxygen and exert nanomaterial-mediated photodynamic therapeutic (NmPDT) complete destruction of solid tumors in mice. The modes of NmPDT and NmPTT can be controlled and switched from one to the other by changing the excitation wavelength. In the in vitro experiments, gold nanocages and nanorod-in-shell show larger percentage of cellular deaths originating from NmPDT along with the minor fraction of NmPTT effects. In contrast, nanoparticle-in-shell exhibits larger fraction of NmPTT-induced cellular deaths together with minor fraction of NmPDT-induced apoptosis. Fluorescence emission spectra and DPBF quenching studies confirm the generation of singlet O2 upon NIR photoirradiation. Both NmPDT and NmPTT effects were confirmed by measurements of reactive oxygen species (ROS) and subsequent sodium azide quenching, heat shock protein expression (HSP 70), singlet oxygen sensor green (SOSG) sensing, changes in mitochondria membrane potential and apoptosis in the cellular experiments. In vivo experiments further demonstrate that upon irradiation at 980 nm under ultra-low doses (∼150 mW/cm(2)), gold nanocages mostly exert NmPDT effect to effectively suppress the B16F0 melanoma tumor growth. The combination of NmPDT and NmPTT effects on destruction of solid tumors is far better than pure NmPTT effect by 808 nm irradiation and also doxorubicin. Overall, our study demonstrates that gold nanoshells can serve as excellent multi-functional theranostic agents (fluorescence imaging + NmPDT + NmPTT) upon single photon NIR light excitation under ultra-low laser doses. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quintet multiexciton dynamics in singlet fission

DOE PAGES

Tayebjee, Murad J. Y.; Sanders, Samuel N.; Kumarasamy, Elango; ...

2016-10-17

Singlet fission, in which two triplet excitons are generated from a single absorbed photon, is a key third-generation solar cell concept. Conservation of angular momentum requires that singlet fission populates correlated multiexciton states, which can subsequently dissociate to generate free triplets. However, little is known about electronic and spin correlations in these systems since, due to its typically short lifetime, the multiexciton state is challenging to isolate and study. Here, we use bridged pentacene dimers, which undergo intramolecular singlet fission while isolated in solution and in solid matrices, as a unimolecular model system that can trap long-lived multiexciton states. Wemore » also combine transient absorption and time-resolved electron spin resonance spectroscopies to show that spin correlations in the multiexciton state persist for hundreds of nanoseconds. Furthermore, we confirm long-standing predictions that singlet fission produces triplet pair states of quintet character. Finally, we compare two different pentacene–bridge–pentacene chromophores, systematically tuning the coupling between the pentacenes to understand how differences in molecular structure affect the population and dissociation of multiexciton quintet states.« less

Spin nematics next to spin singlets

NASA Astrophysics Data System (ADS)

Yokoyama, Yuto; Hotta, Chisa

2018-05-01

We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

Singlet model interference effects with high scale UV physics

DOE PAGES

Dawson, S.; Lewis, I. M.

2017-01-06

One of the simplest extensions of the Standard Model (SM) is the addition of a scalar gauge singlet, S . If S is not forbidden by a symmetry from mixing with the Standard Model Higgs boson, the mixing will generate non-SM rates for Higgs production and decays. Generally, there could also be unknown high energy physics that generates additional effective low energy interactions. We show that interference effects between the scalar resonance of the singlet model and the effective field theory (EFT) operators can have significant effects in the Higgs sector. Here, we examine a non- Z 2 symmetricmore » scalar singlet model and demonstrate that a fit to the 125 GeV Higgs boson couplings and to limits on high mass resonances, S , exhibit an interesting structure and possible large cancellations of effects between the resonance contribution and the new EFT interactions, that invalidate conclusions based on the renormalizable singlet model alone.« less

The mechanism of oxidation in chromophore maturation of wild-type green fluorescent protein: a theoretical study.

PubMed

Ma, Yingying; Sun, Qiao; Smith, Sean C

2017-05-24

Oxidation is viewed as the second and rate-limiting step in the chromophore maturation process of the wild-type green fluorescent protein (GFP) under aerobic conditions. Molecular oxygen is the necessary oxidant for GFP chromophore biosynthesis. In this study, density functional theory (DFT) calculations were employed to study the mechanism of oxidation. Our results indicate that the deprotonation of the Tyr66 α-carbon is probably the rate-limiting step in the oxidation step. Electron transfer from the enolate form of the five-membered heterocycle (EFMH) to molecular oxygen, generating the triplet radical complex [EFMH˙O 2 - ˙] T , is an important step. This complex undergoes intersystem crossing to form an open-shell singlet diradical complex before it forms the closed-shell singlet hydroperoxy adduct. The formation of the hydroperoxy adduct is a proton-coupled electron transfer process. The energy barrier of H 2 O 2 elimination is 16.5 kcal mol -1 . The oxidation product IFMHH 2 O 2 that we discovered is a hydroxylated cyclic imine structure, which is consistent with the crystal structure trapped in the colorless Y66L variant. The relative energy of the oxidation product is -48.7 kcal mol -1 , which is in accordance with the experimental observation that the thermodynamically unfavourable cyclized product is trapped by oxidation. The results herein support the cyclization-oxidation-dehydration mechanism for the chromophore maturation of GFP.

The decomposition of peroxynitrite to nitroxyl anion (NO−) and singlet oxygen in aqueous solution

PubMed Central

Khan, Ahsan Ullah; Kovacic, Dianne; Kolbanovskiy, Alexander; Desai, Mehul; Frenkel, Krystyna; Geacintov, Nicholas E.

2000-01-01

The mechanism of decomposition of peroxynitrite (OONO−) in aqueous sodium phosphate buffer solution at neutral pH was investigated. The OONO− was synthesized by directly reacting nitric oxide with superoxide anion at pH 13. The hypothesis was explored that OONO−, after protonation at pH 7.0 to HOONO, decomposes into 1O2 and HNO according to a spin-conserved unimolecular mechanism. Small aliquots of the concentrated alkaline OONO− solution were added to a buffer solution (final pH 7.0–7.2), and the formation of 1O2 and NO− in high yields was observed. The 1O2 generated was trapped as the transannular peroxide (DPAO2) of 9,10-diphenylanthracene (DPA) dissolved in carbon tetrachloride. The nitroxyl anion (NO−) formed from HNO (pKa 4.5) was trapped as nitrosylhemoglobin (HbNO) in an aqueous methemoglobin (MetHb) solution. In the presence of 25 mM sodium bicarbonate, which is known to accelerate the rate of decomposition of OONO−, the amount of singlet oxygen trapped was reduced by a factor of ≈2 whereas the yield of trapping of NO− by methemoglobin remained unaffected. Because NO3− is known to be the ultimate decomposition product of OONO−, these results suggest that the nitrate anion is not formed by a direct isomerization of OONO−, but by an indirect route originating from NO−. PMID:10716721

Novel DNA lesions generated by the interaction between therapeutic thiopurines and UVA light.

PubMed

Zhang, Xiaohong; Jeffs, Graham; Ren, Xiaolin; O'Donovan, Peter; Montaner, Beatriz; Perrett, Conal M; Karran, Peter; Xu, Yao-Zhong

2007-03-01

The therapeutic effect of the thiopurines, 6-thioguanine (6-TG), 6-mercaptopurine, and its prodrug azathioprine, depends on the incorporation of 6-TG into cellular DNA. Unlike normal DNA bases, 6-TG absorbs UVA radiation, and UVA-mediated photochemical damage of DNA 6-TG has potentially harmful side effects. When free 6-TG is UVA irradiated in solution in the presence of molecular oxygen, reactive oxygen species are generated and 6-TG is oxidized to guanine-6-sulfonate (G(SO3)) and guanine-6-thioguanine in reactions involving singlet oxygen. This conversion is prevented by antioxidants, including the dietary vitamin ascorbate. DNA G(SO3) is also the major photoproduct of 6-TG in DNA and it can be selectively introduced into DNA or oligonucleotides in vitro by mild chemical oxidation. Thermal stability measurements indicate that G(SO3) does not form stable base pairs with any of the normal DNA bases in duplex oligonucleotides and is a powerful block for elongation by Klenow DNA polymerase in primer extension experiments. In cultured human cells, DNA damage produced by 6-TG and UVA treatment is associated with replication inhibition and provokes a p53-dependent DNA damage response.

Core-shell AgSiO2-protoporphyrin IX nanoparticle: Effect of the Ag core on reactive oxygen species generation

NASA Astrophysics Data System (ADS)

Lismont, M.; Pá; ez-Martinez, C.; Dreesen, L.

2015-03-01

Photodynamic therapy (PDT) for cancer is based on the use of a light sensitive molecule to produce, under specific irradiation, toxic reactive oxygen species (ROS). A way to improve the therapy efficiency is to increase the amount of produced ROS near cancer cells. This aim can be achieved by using a metal enhanced process arising when an optically active molecule is located near a metallic nanoparticle (NP). Here, the coupling effect between silver (Ag) NPs and protoporphyrin IX (PpIX) molecules, a clinically approved photosensitizer, is studied compared first, to PpIX fluorescence yield and second, to ROS production efficiency. By applying a modified Stöber process, PpIX was encapsulated into a silica (SiO2) shell, surrounding a 60 nm sized Ag core. We showed that, compared to SiO2-PpIX NPs, Ag coated SiO2-PpIX NPs dramatically decreased PpIX fluorescence together with singlet oxygen production efficiency. However, after incubation time in the dark, the amount of superoxide anions generated by the Ag doped sample was higher than the control sample one.

Uncovering the Roles of Oxygen in Cr(III) Photoredox Catalysis.

PubMed

Higgins, Robert F; Fatur, Steven M; Shepard, Samuel G; Stevenson, Susan M; Boston, David J; Ferreira, Eric M; Damrauer, Niels H; Rappé, Anthony K; Shores, Matthew P

2016-04-27

A combined experimental and theoretical investigation aims to elucidate the necessary roles of oxygen in photoredox catalysis of radical cation based Diels-Alder cycloadditions mediated by the first-row transition metal complex [Cr(Ph2phen)3](3+), where Ph2phen = bathophenanthroline. We employ a diverse array of techniques, including catalysis screening, electrochemistry, time-resolved spectroscopy, and computational analyses of reaction thermodynamics. Our key finding is that oxygen acts as a renewable energy and electron shuttle following photoexcitation of the Cr(III) catalyst. First, oxygen quenches the excited Cr(3+)* complex; this energy transfer process protects the catalyst from decomposition while preserving a synthetically useful 13 μs excited state and produces singlet oxygen. Second, singlet oxygen returns the reduced catalyst to the Cr(III) ground state, forming superoxide. Third, the superoxide species reduces the Diels-Alder cycloadduct radical cation to the final product and reforms oxygen. We compare the results of these studies with those from cycloadditions mediated by related Ru(II)-containing complexes and find that the distinct reaction pathways are likely part of a unified mechanistic framework where the photophysical and photochemical properties of the catalyst species lead to oxygen-mediated photocatalysis for the Cr-containing complex but radical chain initiation for the Ru congener. These results provide insight into how oxygen can participate as a sustainable reagent in photocatalysis.

Pegylated and nanoparticle-conjugated sulfonium salt photo triggers necrotic cell death.

PubMed

Fadhel, Alaa A; Yue, Xiling; Ghazvini Zadeh, Ebrahim H; Bondar, Mykhailo V; Belfield, Kevin D

Photodynamic therapy (PDT) processes involving the production of singlet oxygen face the issue of oxygen concentration dependency. Despite high oxygen delivery, a variety of properties related to metabolism and vascular morphology in cancer cells result in hypoxic environments, resulting in limited effectiveness of such therapies. An alternative oxygen-independent agent whose cell cytotoxicity can be remotely controlled by light may allow access to treatment of hypoxic tumors. Toward that end, we developed and tested both polyethylene glycol (PEG)-functionalized and hydrophilic silica nanoparticle (SiNP)-enriched photoacid generator (PAG) as a nontraditional PDT agent to effectively induce necrotic cell death in HCT-116 cells. Already known for applications in lithography and cationic polymerization, our developed oxygen-independent PDT, whether free or highly monodispersed on SiNPs, generates acid when a one-photon (1P) or two-photon (2P) excitation source is used, thus potentially permitting deep tissue treatment. Our study shows that when conjugated to SiNPs with protruding amine functionalities (SiNP-PAG9), such atypical PDT agents can be effectively delivered into HCT-116 cells and compartmentalize exclusively in lysosomes and endosomes. Loss of cell adhesion and cell swelling are detected when an excitation source is applied, suggesting that SiNP-PAG9, when excited via near-infrared 2P absorption (a subject of future investigation), can be used as a delivery system to selectively induce cell death in oxygen-deprived optically thick tissue.

Core-shell poly-methylmethacrylate nanoparticles as effective carriers of electrostatically loaded anionic porphyrin.

PubMed

Varchi, Greta; Benfenati, Valentina; Pistone, Assunta; Ballestri, Marco; Sotgiu, Giovanna; Guerrini, Andrea; Dambruoso, Paolo; Liscio, Andrea; Ventura, Barbara

2013-05-01

Among the medical applications of nanoparticles, their usage as photosensitizer (PS) carriers for photodynamic therapy (PDT) has attracted increasing attention. In the present study we explored the morphological and photophysical properties of core-shell PMMA nanoparticles (PMMA-NPs) electrostatically post-loaded with the synthetic, water soluble 5,10,15,20-tetrakis(4-sulphonatophenyl)-porphyrin (TPPS4). pH response and singlet oxygen analyses of differently loaded samples proved the high capability of the PMMA-NPs to shield the PS from the environment, while retaining the PS singlet oxygen production capability. Preliminary in vitro imaging and phototoxicity experiments on HepG2 cells demonstrated the efficacy of the system to trigger photoinduced cell death in the culture.

Colloidal plasmonic gold nanoparticles and gold nanorings: shape-dependent generation of singlet oxygen and their performance in enhanced photodynamic cancer therapy.

PubMed

Yang, Yamin; Hu, Yue; Du, Henry; Ren, Lei; Wang, Hongjun

2018-01-01

In recognition of the potentials of gold nanoparticles (Au NPs) in enhanced photodynamic therapy (PDT) for cancer, it is desirable to further understand the shape-dependent surface plasmonic resonance (SPR) properties of various gold nanostructures and evaluate their performances in PDT. Monodispersed colloidal spherical solid Au NPs were synthesized by UV-assisted reduction using chloroauric acid and sodium citrate, and hollow gold nanorings (Au NRs) with similar outer diameter were synthesized based on sacrificial galvanic replacement method. The enhanced electromagnetic (EM) field distribution and their corresponding efficiency in enhancing singlet oxygen ( 1 O 2 ) generation of both gold nanostructures were investigated based on theoretical simulation and experimental measurements. Their shape-dependent SPR response and resulted cell destruction during cellular PDT in combination with 5-aminolevulinic acid (5-ALA) were further studied under different irradiation conditions. With comparable cellular uptake, more elevated formation of 1 O 2 in 5-ALA-enabled PDT was detected with the presence of Au NRs than that with Au NPs under broadband light irradiation in both cell-free and intracellular conditions. As a result of the unique morphological attributes, exhibiting plasmonic effect of Au NRs was still achievable in the near infrared (NIR) region, which led to an enhanced therapeutic efficacy of PDT under NIR light irradiation. Shape-dependent SPR response of colloidal Au NPs and Au NRs and their respective effects in promoting PDT efficiency were demonstrated in present study. Our innovative colloidal Au NRs with interior region accessible to surrounding photosensitizers would serve as efficient enhancers of PDT potentially for deep tumor treatment.

Detection and identification of 1-methylethyl and methyl radicals generated by irradiating tea tree (Melaleuca alternifolia) oil with visible light (436 nm) in the presence of flavin mononucleotide and ferrous ion.

PubMed

Mori, H-M; Iwahashi, H

2013-08-01

Here, we determined the electron spin resonance (ESR) spectra of standard reaction mixtures (I) containing 25 μM flavin mononucleotide (FMN), 0.018% tea tree (Melaleuca alternifolia) oil, 1.9 M acetonitrile, 20 mM phosphate buffer (pH 7.4), 0.1 M α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN), and 1.0 mM FeSO₄(NH₄)₂SO₄ irradiated with 436 nm visible light (7.8 J/cm²). Prominent ESR signals (αN = 1.58 mT and αHβ = 0.26 mT) were detected, suggesting that free radicals form in the standard reaction. In order to know whether singlet oxygen (¹O₂) is involved in the radical formation or not, ESR measurement was performed for the standard D₂O reaction mixture (I) which contained 25 μM FMN, 0.0036% tea tree oil, 1.9 M acetonitrile-d3, 20 mM phosphate buffer (pH 7.4), 0.1 M 4-POBN and 1.0 mM FeSO₄ in D₂O. The ESR peak height of the standard D₂O reaction increased to 169 ± 24% of the control. Thus, ¹O₂ seems to be involved in the formation of the radicals because D₂O increases the lifetime of singlet oxygen. High-performance liquid chromatography-ESR-mass spectrometry analyses detected 1-methylethyl and methyl radicals in the standard reaction. The radicals appear to form through the reaction of ferrous ion with α-terpinene endoperoxide (ascaridole), which generated from the reaction of α-terpinene with ¹O₂. The 1-methylethyl and methyl radicals may exert a pro-oxidant effect under these conditions.

Colloidal plasmonic gold nanoparticles and gold nanorings: shape-dependent generation of singlet oxygen and their performance in enhanced photodynamic cancer therapy

PubMed Central

Yang, Yamin; Hu, Yue; Du, Henry; Ren, Lei; Wang, Hongjun

2018-01-01

Introduction In recognition of the potentials of gold nanoparticles (Au NPs) in enhanced photodynamic therapy (PDT) for cancer, it is desirable to further understand the shape-dependent surface plasmonic resonance (SPR) properties of various gold nanostructures and evaluate their performances in PDT. Materials and methods Monodispersed colloidal spherical solid Au NPs were synthesized by UV-assisted reduction using chloroauric acid and sodium citrate, and hollow gold nanorings (Au NRs) with similar outer diameter were synthesized based on sacrificial galvanic replacement method. The enhanced electromagnetic (EM) field distribution and their corresponding efficiency in enhancing singlet oxygen (1O2) generation of both gold nanostructures were investigated based on theoretical simulation and experimental measurements. Their shape-dependent SPR response and resulted cell destruction during cellular PDT in combination with 5-aminolevulinic acid (5-ALA) were further studied under different irradiation conditions. Results With comparable cellular uptake, more elevated formation of 1O2 in 5-ALA-enabled PDT was detected with the presence of Au NRs than that with Au NPs under broadband light irradiation in both cell-free and intracellular conditions. As a result of the unique morphological attributes, exhibiting plasmonic effect of Au NRs was still achievable in the near infrared (NIR) region, which led to an enhanced therapeutic efficacy of PDT under NIR light irradiation. Conclusion Shape-dependent SPR response of colloidal Au NPs and Au NRs and their respective effects in promoting PDT efficiency were demonstrated in present study. Our innovative colloidal Au NRs with interior region accessible to surrounding photosensitizers would serve as efficient enhancers of PDT potentially for deep tumor treatment. PMID:29670350

Reactive oxygen species: role in the development of cancer and various chronic conditions

PubMed Central

Waris, Gulam; Ahsan, Haseeb

2006-01-01

Oxygen derived species such as superoxide radical, hydrogen peroxide, singlet oxygen and hydroxyl radical are well known to be cytotoxic and have been implicated in the etiology of a wide array of human diseases, including cancer. Various carcinogens may also partly exert their effect by generating reactive oxygen species (ROS) during their metabolism. Oxidative damage to cellular DNA can lead to mutations and may, therefore, play an important role in the initiation and progression of multistage carcinogenesis. The changes in DNA such as base modification, rearrangement of DNA sequence, miscoding of DNA lesion, gene duplication and the activation of oncogenes may be involved in the initiation of various cancers. Elevated levels of ROS and down regulation of ROS scavengers and antioxidant enzymes are associated with various human diseases including various cancers. ROS are also implicated in diabtes and neurodegenerative diseases. ROS influences central cellular processes such as proliferation a, apoptosis, senescence which are implicated in the development of cancer. Understanding the role of ROS as key mediators in signaling cascades may provide various opportunities for pharmacological intervention. PMID:16689993

Cholesterol and related sterols autoxidation.

PubMed

Zerbinati, Chiara; Iuliano, Luigi

2017-10-01

Cholesterol is a unique lipid molecule providing the building block for membranes, hormones, vitamin D and bile acid synthesis. Metabolism of cholesterol involves several enzymes acting on the sterol nucleus or the isooctyl tail. In the recent years, research interest has been focused on oxysterols, cholesterol derivatives generated by the addition of oxygen to the cholesterol backbone. Oxysterols can be produced enzymatically or by autoxidation. Autoxidation of cholesterol proceeds through type I or type II mechanisms. Type I autoxidation is initiated by free radical species, such as those arising from the superoxide/hydrogen peroxide/hydroxyl radical system. Type II autoxidation occurs stoichiometrically by non-radical highly reactive oxygen species such as singlet oxygen, HOCl, and ozone. The vulnerability of cholesterol towards high reactive species has raised considerable interest for mechanistic studies and for the potential biological activity of oxysterols, as well as for the use of oxysterols as biomarkers for the non-invasive study of oxidative stress in vivo. Copyright © 2017. Published by Elsevier Inc.

Cooperative Singlet and Triplet Exciton Transport in Tetracene Crystals Visualized by Ultrafast Microscopys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Yan; Guo, Zhi; Zhu, Tong

2015-09-14

Singlet fission presents an attractive solution to overcome the Shockley–Queisser limit by generating two triplet excitons from one singlet exciton. Although triplet excitons are long-lived, their transport occurs through a Dexter transfer, making them slower than singlet excitons, which travel by means of a Förster mechanism. A thorough understanding of the interplay between singlet fission and exciton transport is therefore necessary to assess the potential and challenges of singlet-fission utilization. We report a direct visualization of exciton transport in single tetracene crystals using transient absorption microscopy with 200 fs time resolution and 50 nm spatial precision. Moreover, these measurements revealmore » a new singlet-mediated transport mechanism for triplets, which leads to an enhancement in effective triplet exciton diffusion of more than one order of magnitude on picosecond to nanosecond timescales. These results establish that there are optimal energetics of singlet and triplet excitons that benefit both singlet fission and exciton diffusion.« less

Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy

NASA Astrophysics Data System (ADS)

Wan, Yan; Guo, Zhi; Zhu, Tong; Yan, Suxia; Johnson, Justin; Huang, Libai

2015-10-01

Singlet fission presents an attractive solution to overcome the Shockley-Queisser limit by generating two triplet excitons from one singlet exciton. However, although triplet excitons are long-lived, their transport occurs through a Dexter transfer, making them slower than singlet excitons, which travel by means of a Förster mechanism. A thorough understanding of the interplay between singlet fission and exciton transport is therefore necessary to assess the potential and challenges of singlet-fission utilization. Here, we report a direct visualization of exciton transport in single tetracene crystals using transient absorption microscopy with 200 fs time resolution and 50 nm spatial precision. These measurements reveal a new singlet-mediated transport mechanism for triplets, which leads to an enhancement in effective triplet exciton diffusion of more than one order of magnitude on picosecond to nanosecond timescales. These results establish that there are optimal energetics of singlet and triplet excitons that benefit both singlet fission and exciton diffusion.

Capturing Transient Endoperoxide in the Singlet Oxygen Oxidation of Guanine.

PubMed

Lu, Wenchao; Liu, Jianbo

2016-02-24

The chemistry of singlet O2 toward the guanine base of DNA is highly relevant to DNA lesion, mutation, cell death, and pathological conditions. This oxidative damage is initiated by the formation of a transient endoperoxide through the Diels-Alder cycloaddition of singlet O2 to the guanine imidazole ring. However, no endoperoxide formation was directly detected in native guanine or guanosine, even at -100 °C. Herein, gas-phase ion-molecule scattering mass spectrometry was utilized to capture unstable endoperoxides in the collisions of hydrated guanine ions (protonated or deprotonated) with singlet O2 at ambient temperature. Corroborated by results from potential energy surface exploration, kinetic modeling, and dynamics simulations, various aspects of endoperoxide formation and transformation (including its dependence on guanine ionization and hydration states, as well as on collision energy) were determined. This work has pieced together reaction mechanisms, kinetics, and dynamics data concerning the early stage of singlet O2 induced guanine oxidation, which is missing from conventional condensed-phase studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Synthesis and Photophysical Characterization of Porphyrin Photoactive Materials for Use as Sensitizers in Organic Photovoltaics and Photodynamic Therapy

NASA Astrophysics Data System (ADS)

Marin, Dawn Marie

Solar energy conversion and photodynamic therapy (PDT) are very different applications. However, both utilize very similar photoactive molecules called porphyrins. Porphyrins are structural analogs of chlorophyll and also function as prosthetic groups in some biological enzymes. Understanding the structure/function relationship of these molecules is crucial for enhancing the energy generation efficiency of molecular solar cells and improving chemotherapeutic activity in PDT. In this dissertation, two approaches were applied with the goal of increasing the efficiency of molecular semiconductors for these applications: the heavy atom effect and donor-acceptor molecules. We enhanced the efficiency of triplet excited state formation and singlet oxygen generation for porphyrin sensitizers using the heavy atom effect. The heavy atom effect induces spin-orbit coupling to promote intersystem crossing into the triplet state. In this study, a carbomethoxyphenyl substituent was replaced with either a bromophenyl or an iodophenyl substituent on 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin. The longer lifetimes obtained from the increase in the triplet excited state allow for longer exciton diffusion lengths and lower recombination rates in photovoltaics. Also, the enhanced intersystem crossing is beneficial for photodynamic therapy because it increases singlet oxygen generation, which destroys tumor cells. Optimizing photovoltaic performance and PDT efficacy can also be accomplished with donor-acceptor molecules because they have extended electronic pi bond delocalization across the molecule, which causes the molecule to absorb longer wavelengths of light. Donor-acceptor molecules should produce photovoltaic devices that absorb more of the solar spectrum and produce sensitizers that absorb wavelengths of light that can penetrate through tissues. Donor-acceptor molecules were synthesized using 5,15-bis(4-carbomethoxyphenyl)porphyrin as the acceptor and thiazolo[5,4-d]thiazole derivatives as the donor. The excited state dynamics of the heavy atom derivatives and donor-acceptor molecules were studied using UV-vis spectroscopy, steady-state emission, time-resolved and delayed photoluminescence.

Light-controlled drug release from singlet-oxygen sensitive nanoscale coordination polymers enabling cancer combination therapy.

PubMed

Liu, Jingjing; Yang, Guangbao; Zhu, Wenwen; Dong, Ziliang; Yang, Yu; Chao, Yu; Liu, Zhuang

2017-11-01

The development of smart drug delivery systems to realize controlled drug release for highly specific cancer treatment has attracted tremendous attention. Herein, nanoscale coordination polymers (NCPs) constructed from hafnium ions and bis-(alkylthio) alkene (BATA), a singlet-oxygen responsive linker, are fabricated and applied as nanocarriers to realize light-controlled drug release under a rather low optical power density. In this system, NCPs synthesized through a solvothermal method are sequentially loaded with chlorin e6 (Ce6), a photosensitizer, and doxorubicin (DOX), a chemotherapeutic drug, and then coated with lipid bilayer to allow modification with polyethylene glycol (PEG) to acquire excellent colloidal stability. The singlet oxygen produced by such NCP-Ce6-DOX-PEG nanocomposite can be used not only for photodynamic therapy, but also to induce the break of BATA linker and thus the destruction of nanoparticle structures under light exposure, thereby triggering effective drug release. Notably, with efficient tumor accumulation after intravenous injection as revealed by CT imaging, those NCP-Ce6-DOX-PEG nanoparticles could be utilized for combined chemo-photodynamic therapy with great antitumor efficacy. Thus, this work presents a unique type of NCP-based drug delivery system with biodegradability, sensitive responses to light, as well as highly efficient tumor retention for effective cancer combinational treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Inhibition of plasma lipid oxidation induced by peroxyl radicals, peroxynitrite, hypochlorite, 15-lipoxygenase, and singlet oxygen by clinical drugs.

PubMed

Morita, Mayuko; Naito, Yuji; Yoshikawa, Toshikazu; Niki, Etsuo

2016-11-15

With increasing evidence showing the involvement of oxidative stress in the pathogenesis of various diseases, the effects of clinical drugs possessing antioxidant functions have received much attention. The unregulated oxidative modification of biological molecules leading to diseases is mediated by multiple oxidants including free radicals, peroxynitrite, hypochlorite, lipoxygenase, and singlet oxygen. The capacity of antioxidants to scavenge or quench oxidants depends on the nature of oxidants. In the present study, the antioxidant effects of several clinical drugs against plasma lipid oxidation induced by the aforementioned five kinds of oxidants were investigated from the production of lipid hydroperoxides, which have been implicated in the pathogenesis of various diseases. Troglitazone acted as a potent peroxyl radical scavenger, whereas probucol and edaravone showed only moderate reactivity and carvedilol, pentoxifylline, and ebselen did not act as radical scavenger. Probucol and edaravone suppressed plasma oxidation mediated by peroxynitrite and hypochlorite. Troglitazone and edaravone inhibited 15-lipoxygenase mediated plasma lipid oxidation, the IC 50 being 20 and 34μM respectively. None of the drugs used in this study suppressed plasma lipid oxidation by singlet oxygen. This study shows that the antioxidant effects of drugs depend on the nature of oxidants and that antioxidants against multiple oxidants are required to cope with oxidative stress in vivo. Copyright © 2016 Elsevier Ltd. All rights reserved.

Validation of photodynamic action via photobleaching of a new curcumin-based composite with enhanced water solubility.

PubMed

Rego-Filho, Francisco G; de Araujo, Maria T; de Oliveira, Kleber T; Bagnato, Vanderlei S

2014-09-01

Motivated by the photochemical and photophysical properties of curcumin-based composites, the characteristics of a new curcumin-based water-soluble salt were investigated via absorption and fluorescence spectroscopy. Photobleaching was investigated using a set of LEDs in three different wavelengths (405 nm, 450 nm and 470 nm) to illuminate an aqueous solution of curcumin, evaluating its degradation for five different exposure times (0, 5, 15, 45 and 105 minutes). The results were compared with equivalent measurements of dark degradation and illumination in the presence of a singlet-oxygen quencher. Three solution concentrations (50, 100 and 150 μg/ml) were studied. To measure the fluorescence, it was used low power 405 nm excitation laser source. Time dependent photodegradation of curcumin was observed, as compared to the natural degradation of samples maintained on a dark environment. Two main absorption peaks were detected and their relation responded to both concentration and wavelength of the illumination source. A spectral correlation between absorption of curcumin and the emission bands of the sources showed an optimal spectral overlap for the 450 nm LED. For this source, photobleaching showed a less intense degradation on the presence of singlet oxygen quencher. This last result confirmed singlet oxygen production in vitro, indicating a strong potential of this composite to be used as a blue-light-activated photosensitizer.

Hydrogen Bond Acceptors and Additional Cationic Charges in Methylene Blue Derivatives: Photophysics and Antimicrobial Efficiency

PubMed Central

Felgenträger, Ariane; Maisch, Tim; Dobler, Daniel; Späth, Andreas

2013-01-01

Photodynamic inactivation of bacteria (PIB) by efficient singlet oxygen photosensitizers might be a beneficial alternative to antibiotics in the struggle against multiresistant bacteria. Phenothiazinium dyes belong to the most prominent classes of such sensitizers due to their intense absorption in the red-light region (λ abs, max ca. 600–680 nm, ε > 50000 L mol−1 cm−1), their low toxicity, and their attachment/penetration abilities. Except simple substituents like alkyl or hydroxyalkyl residues, nearly no modifications of the phenothiaziniums have been pursued at the auxochromic sites. By this, the properties of methylene blue derivatives and their fields of application are limited; it remains unclear if their potential antimicrobial efficacy may be enhanced, also to compete with porphyrins. We prepared a set of six mainly novel methylene blue derivatives with the ability of additional hydrogen bonding and/or additional cationic charges to study the substituents' effect on their activity/toxicity profiles and photophysical properties. Direct detection of singlet oxygen was performed at 1270 nm and the singlet oxygen quantum yields were determined. In suspensions with both, Gram-positive and Gram-negative bacteria, some derivatives were highly active upon illumination to inactivate S. aureus and E. coli up to 7 log10 steps (99.99999%) without inherent toxicities in the nonirradiated state. PMID:23509728

Augmenting the antibiofilm efficacy of advanced noninvasive light activated disinfection with emulsified oxidizer and oxygen carrier.

PubMed

George, Saji; Kishen, Anil

2008-09-01

In this study, we tested the hypothesis that the inclusion of an oxidizer and oxygen carrier in the photosensitization formulation would facilitate comprehensive disinfection of matured endodontic biofilm by light-activated disinfection (LAD). Photosensitizing formulations containing methylene blue (MB) and an oxygen carrier alone (perfluorodecahydronaphthalene) (PF1) or in combination with oxidizer (H(2)O(2)) (PF2) or their emulsions formed with triton-X100 (Bio-Rad Laboratories, Hercules, CA) in different proportions (PF3 and PF4) were tested for photochemical properties and damage to the biofilm structure using confocal laser scanning microscopy. Conventional chemomechanical preparation, LAD using MB in water, and LAD using MB in emulsion (PF4) were also conducted on 10-week-old Enterococcus faecalis biofilm within root canals. MB in emulsion (PF4) was overall the most effective photosensitizer formulation for photooxidation, generation of singlet oxygen (p = 0.001), and in disinfecting biofilm bacteria. Advanced noninvasive LAD using a photosensitizer formulation containing oxidizer and oxygen carrier disrupted the biofilm matrix and facilitated comprehensive inactivation of biofilm bacteria. This modified photosensitizer formulation will have potential advantages in endodontic disinfection.

Symbiodinium sp. cells produce light-induced intra- and extracellular singlet oxygen, which mediates photodamage of the photosynthetic apparatus and has the potential to interact with the animal host in coral symbiosis.

PubMed

Rehman, Ateeq Ur; Szabó, Milán; Deák, Zsuzsanna; Sass, László; Larkum, Anthony; Ralph, Peter; Vass, Imre

2016-10-01

Coral bleaching is an important environmental phenomenon, whose mechanism has not yet been clarified. The involvement of reactive oxygen species (ROS) has been implicated, but direct evidence of what species are involved, their location and their mechanisms of production remains unknown. Histidine-mediated chemical trapping and singlet oxygen sensor green (SOSG) were used to detect intra- and extracellular singlet oxygen ((1) O2 ) in Symbiodinium cultures. Inhibition of the Calvin-Benson cycle by thermal stress or high light promotes intracellular (1) O2 formation. Histidine addition, which decreases the amount of intracellular (1) O2 , provides partial protection against photosystem II photoinactivation and chlorophyll (Chl) bleaching. (1) O2 production also occurs in cell-free medium of Symbiodinium cultures, an effect that is enhanced under heat and light stress and can be attributed to the excretion of (1) O2 -sensitizing metabolites from the cells. Confocal microscopy imaging using SOSG showed most extracellular (1) O2 around the cell surface, but it is also produced across the medium distant from the cells. We demonstrate, for the first time, both intra- and extracellular (1) O2 production in Symbiodinium cultures. Intracellular (1) O2 is associated with photosystem II photodamage and pigment bleaching, whereas extracellular (1) O2 has the potential to mediate the breakdown of symbiotic interaction between zooxanthellae and their animal host during coral bleaching. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Thiocyanate potentiates antimicrobial photodynamic therapy: In situ generation of the sulfur trioxide radical anion by singlet oxygen

PubMed Central

St Denis, Tyler G.; Vecchio, Daniela; Zadlo, Andrzej; Rineh, Ardeshir; Sadasivam, Magesh; Avci, Pinar; Huang, Liyi; Kozinska, Anna; Chandran, Rakkiyappan; Sarna, Tadeusz; Hamblin, Michael R.

2013-01-01

Antimicrobial photodynamic therapy (PDT) is used for the eradication of pathogenic microbial cells and involves the light excitation of dyes in the presence of O2, yielding reactive oxygen species including the hydroxyl radical (•OH) and singlet oxygen (1O2). In order to chemically enhance PDT by the formation of longer-lived radical species, we asked whether thiocyanate (SCN−) could potentiate the methylene blue (MB) and light-mediated killing of the gram-positive Staphylococcus aureus and the gram-negative Escherichia coli. SCN− enhanced PDT (10 μM MB, 5J/cm2 660 nm hv) killing in a concentration-dependent manner of S. aureus by 2.5 log10 to a maximum of 4.2 log10 at 10 mM (P < 0.001) and increased killing of E. coli by 3.6 log10 to a maximum of 5.0 log10 at 10 mM (P < 0.01). We determined that SCN− rapidly depleted O2 from an irradiated MB system, reacting exclusively with 1O2, without quenching the MB excited triplet state. SCN− reacted with 1O2, producing a sulfur trioxide radical anion (a sulfur-centered radical demonstrated by EPR spin trapping). We found that MB-PDT of SCN− in solution produced both sulfite and cyanide anions, and that addition of each of these salts separately enhanced MB-PDT killing of bacteria. We were unable to detect EPR signals of •OH, which, together with kinetic data, strongly suggests that MB, known to produce •OH and 1O2, may, under the conditions used, preferentially form 1O2. PMID:23969112

Effect of intramolecular charge transfer on fluorescence and singlet oxygen production of phthalocyanine analogues.

PubMed

Vachova, Lenka; Novakova, Veronika; Kopecky, Kamil; Miletin, Miroslav; Zimcik, Petr

2012-10-14

Intramolecular charge transfer (ICT) was studied on a series of magnesium, metal-free and zinc complexes of unsymmetrical tetrapyrazinoporphyrazines and tribenzopyrazinoporphyrazines bearing two dialkylamino substituents (donors) and six alkylsulfanyl or aryloxy substituents (non-donors). The dialkylamino substituents were responsible for ICT that deactivated excited states and led to considerable decrease of fluorescence and singlet oxygen quantum yields. Photophysical and photochemical properties were compared to corresponding macrocycles that do not bear any donor centers. The data showed high feasibility of ICT in the tetrapyrazinoporphyrazine macrocycle and significantly lower efficiency of this deactivation process in the tribenzopyrazinoporphyrazine type molecules. Considerable effect of non-donor peripheral substituents on ICT was also described. The results imply that tetrapyrazinoporphyrazines may be more suitable for development of new molecules investigated in applications based on ICT.

Novel axially carborane-cage substituted silicon phthalocyanine photosensitizer; synthesis, characterization and photophysicochemical properties

NASA Astrophysics Data System (ADS)

Atmaca, Göknur Yaşa; Dizman, Cemil; Eren, Tarık; Erdoğmuş, Ali

2015-02-01

The novel axially dicarborane substituted silicon (IV) (SiPc-DC) phthalocyanine was synthesized by treating silicon phthalocyanine dichloride SiPc(Cl)2 (SiPc) with o-Carborane monool. The compound was characterized by mass spectrometry, UV-Vis, FT-IR, 1H and 11B Nuclear Magnetic Resonance Spectroscopy (NMR). Spectral, photophysical (fluorescence quantum yield) and photochemical (singlet oxygen (ΦΔ) and photodegradation quantum yield (Φd)) properties of the complex were reported in different solutions (Dimethyl sulfoxide (DMSO), Dimethylformamide (DMF) and Toluene). The results of spectral measurements showed that both SiPc and carborane cage can have potential to be used as sensitizers in photodynamic therapy (PDT) and boron neutron capture therapy (BNCT) by their singlet oxygen efficiencies (ΦΔ = 0.41, 0.39).

Quantum yield and rate constant of the singlet 1Δ g oxygen luminescence in an aqueous medium in the presence of nanoscale inhomogeneities

NASA Astrophysics Data System (ADS)

Jarnikova, E. S.; Parkhats, M. V.; Stasheuski, A. S.; Lepeshkevich, S. V.; Dzhagarov, B. M.

2017-04-01

The quantum yields and lifetimes of photosensitized luminescence of the 1Δ g state of singlet oxygen in an aquatic media with a controlled concentration of dielectric anisotropy centers (polyethylene glycol) have been measured using the methods of laser fluorometry. It is established that the quantum yield and the rate constant ( k r ) of the a 1Δ g → X 3Σ g - luminescence of 1O2 increase as the polymer concentration increases. The effect is analyzed within a general approach involving a relationship between kr and dielectric properties of the medium and is explained by the increased density of photon states and the local field factor in the space around O2( a 1Δ g ).

Products and yields from O3 photodissociation at 1576 A

NASA Technical Reports Server (NTRS)

Taherian, M. R.; Slanger, T. G.

1985-01-01

An analysis has been made of the primary atomic and molecular products arising from O3 photodissociation at 1576 A. The yield of oxygen atoms is 1.90 + or - 0.30, of which 71 percent are O(3P) and 29 percent are O(1D). Since a primary yield greater than unity can only be a consequence of three-fragment dissociation, these results suggest that fragmentation into three O(3P) atoms, and production of O(1D) plus a singlet oxygen molecule, have comparable yields. Observation of prompt emission in the 7300-8100 A spectral region indicates that the singlet O2 is O2(b 1Sigma + g). Vibrational levels in the range v = 0-6 have been detected, the distribution corresponding to a vibrational temperature of 1000 K.

Generation and decay dynamics of triplet excitons in Alq3 thin films under high-density excitation conditions.

PubMed

Watanabe, Sadayuki; Furube, Akihiro; Katoh, Ryuzi

2006-08-31

We studied the generation and decay dynamics of triplet excitons in tris-(8-hydroxyquinoline) aluminum (Alq3) thin films by using transient absorption spectroscopy. Absorption spectra of both singlet and triplet excitons in the film were identified by comparison with transient absorption spectra of the ligand molecule (8-hydroxyquinoline) itself and the excited triplet state in solution previously reported. By measuring the excitation light intensity dependence of the absorption, we found that exciton annihilation dominated under high-density excitation conditions. Annihilation rate constants were estimated to be gammaSS = (6 +/- 3) x 10(-11) cm3 s(-1) for single excitons and gammaTT = (4 +/- 2) x 10(-13) cm3 s(-1) for triplet excitons. From detailed analysis of the light intensity dependence of the quantum yield of triplet excitons under high-density conditions, triplet excitons were mainly generated through fission from highly excited singlet states populated by singlet-singlet exciton annihilation. We estimated that 30% of the highly excited states underwent fission.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tayebjee, Murad J. Y.; Sanders, Samuel N.; Kumarasamy, Elango

Singlet fission, in which two triplet excitons are generated from a single absorbed photon, is a key third-generation solar cell concept. Conservation of angular momentum requires that singlet fission populates correlated multiexciton states, which can subsequently dissociate to generate free triplets. However, little is known about electronic and spin correlations in these systems since, due to its typically short lifetime, the multiexciton state is challenging to isolate and study. Here, we use bridged pentacene dimers, which undergo intramolecular singlet fission while isolated in solution and in solid matrices, as a unimolecular model system that can trap long-lived multiexciton states. Wemore » also combine transient absorption and time-resolved electron spin resonance spectroscopies to show that spin correlations in the multiexciton state persist for hundreds of nanoseconds. Furthermore, we confirm long-standing predictions that singlet fission produces triplet pair states of quintet character. Finally, we compare two different pentacene–bridge–pentacene chromophores, systematically tuning the coupling between the pentacenes to understand how differences in molecular structure affect the population and dissociation of multiexciton quintet states.« less

Luminescence of the (O{sub 2}(a{sup 1}Δ{sub g})){sub 2} collisional complex in the temperature range of 90-315 K: Experiment and theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagidullin, M. V., E-mail: marsel@fian.smr.ru; Pershin, A. A., E-mail: anchizh93@gmail.com; Azyazov, V. N., E-mail: azyazov@ssau.ru

Experimental and theoretical studies of collision induced emission of singlet oxygen molecules O{sub 2}(a{sup 1}Δ{sub g}) in the visible range have been performed. The rate constants, half-widths, and position of peaks for the emission bands of the (O{sub 2}(a{sup 1}Δ{sub g})){sub 2} collisional complex centered around 634 nm (2) and 703 nm (3) have been measured in the temperature range of 90–315 K using a flow-tube apparatus that utilized a gas-liquid chemical singlet oxygen generator. The absolute values of the spontaneous emission rate constants k{sub 2} and k{sub 3} are found to be similar, with the k{sub 3}/k{sub 2} ratiomore » monotonically decreasing from 1.1 at 300 K to 0.96 at 90 K. k{sub 2} slowly decreases with decreasing temperature but a sharp increase in its values is measured below 100 K. The experimental results were rationalized in terms of ab initio calculations of the ground and excited potential energy and transition dipole moment surfaces of singlet electronic states of the (O{sub 2}){sub 2} dimole, which were utilized to compute rate constants k{sub 2} and k{sub 3} within a statistical model. The best theoretical results reproduced experimental rate constants with the accuracy of under 40% and correctly described the observed temperature dependence. The main contribution to emission process (2), which does not involve vibrational excitation of O{sub 2} molecules at the ground electronic level, comes from the spin- and symmetry-allowed 1{sup 1}A{sub g}←{sup 1}B{sub 3u} transition in the rectangular H configuration of the dimole. Alternatively, emission process (3), in which one of the monomers becomes vibrationally excited in the ground electronic state, is found to be predominantly due to the vibronically allowed 1{sup 1}A{sub g}←2{sup 1}A{sub g} transition induced by the asymmetric O–O stretch vibration in the collisional complex. The strong vibronic coupling between nearly degenerate excited singlet states of the dimole makes the intensities of vibronically and symmetry-allowed transitions comparable and hence the rate constants k{sub 2} and k{sub 3} close to one another.« less

Photophysics and photochemistry of dyes bound to human serum albumin are determined by the dye localization.

PubMed

Alarcón, Emilio; Edwards, Ana Maria; Aspee, Alexis; Moran, Faustino E; Borsarelli, Claudio D; Lissi, Eduardo A; Gonzalez-Nilo, Danilo; Poblete, Horacio; Scaiano, J C

2010-01-01

The photophysics and photochemistry of rose bengal (RB) and methylene blue (MB) bound to human serum albumin (HSA) have been investigated under a variety of experimental conditions. Distribution of the dyes between the external solvent and the protein has been estimated by physical separation and fluorescence measurements. The main localization of protein-bound dye molecules was estimated by the intrinsic fluorescence quenching, displacement of fluorescent probes bound to specific protein sites, and by docking modelling. All the data indicate that, at low occupation numbers, RB binds strongly to the HSA site I, while MB localizes predominantly in the protein binding site II. This different localization explains the observed differences in the dyes' photochemical behaviour. In particular, the environment provided by site I is less polar and considerably less accessible to oxygen. The localization of RB in site I also leads to an efficient quenching of the intrinsic protein fluorescence (ascribed to the nearby Trp residue) and the generation of intra-protein singlet oxygen, whose behaviour is different to that observed in the external solvent or when it is generated by bound MB.

Suitability of TBA method for the evaluation of the oxidative effect of non-water-soluble and water-soluble rosemary extracts.

PubMed

Wada, Mitsuhiro; Nagano, Minori; Kido, Hirotsugu; Ikeda, Rie; Kuroda, Naotaka; Nakashima, Kenichiro

2011-01-01

The antioxidative effects of rosemary and grape-seed extracts spiked in human plasma were examined using the thiobarbituric acid (TBA) method. The TBA values of plasma spiked with reagents to generate reactive oxygen species, such as singlet oxygen ((1)O(2)), hydroxyl radicals ((·)OH), peroxynitrite (ONOO(-)), and superoxide anions (O(2)(·-)), were measured by a flow injection analysis method with fluorescence (FL) detection. TBA values obtained by the addition of 50 mg/mL of rosemary extracts for (1)O(2), (·)OH, ONOO(-), and O(2)(·-) increased to 964 ± 65%, 1063 ± 61%, 758 ± 78%, and 698 ± 41%, respectively (n = 3, P < 0.01), whereas the values with 1 mg/mL of grape-seed extracts or tocopherol decreased (40.2 - 66.3%). Furthermore, the antioxidative effects of rosemary extract in rat plasma, spiked with reagents to generate (·)OH, were examined by high-performance liquid chromatography with FL detection. No peak, other than TBA-malondialdehyde, could be detected using wavelengths of 532 (λ(ex)) and 553 nm (λ(em)).

Blue light irradiation-induced oxidative stress in vivo via ROS generation in rat gingival tissue.

PubMed

Yoshida, Ayaka; Shiotsu-Ogura, Yukako; Wada-Takahashi, Satoko; Takahashi, Shun-suke; Toyama, Toshizo; Yoshino, Fumihiko

2015-10-01

It has been reported that oxidative stress with reactive oxygen species (ROS) generation is induced by blue light irradiation to a living body. Only limited research has been reported in dental field on the dangers of blue light, mostly focusing on cytotoxicity associated with heat injury of dental pulp. We thus performed an in vivo study on oral tissue exposed to blue light. ROS generated upon blue light irradiation of flavin adenine dinucleotide were measured by electron spin resonance spectroscopy. After blue light irradiation, the palatal gingiva of Wistar rats were isolated. Collected samples were subjected to biochemical analysis of lipid peroxidation and glutathione. Singlet oxygen was generated by blue light irradiation, but was significantly quenched in an N-acetyl-L-cysteine (NAC) concentration-dependent manner. Blue light significantly accelerated oxidative stress and increased the oxidized glutathione levels in gingival tissue. These effects were also inhibited by NAC pre-administration. The results suggest that blue light irradiation at clinical levels of tooth bleaching treatment may enhance lipid peroxidation by the induction of oxidative stress and the consumption of a significant amount of intracellular glutathione. In addition, NAC might be an effective supplement for the protection of oral tissues against blue light irradiation-induced oxidative damage. Copyright © 2015 Elsevier B.V. All rights reserved.

Time-gated luminescence imaging of singlet oxygen photoinduced by fluoroquinolones and functionalized graphenes in Daphnia magna.

PubMed

Luo, Tianlie; Chen, Jingwen; Song, Bo; Ma, Hua; Fu, Zhiqiang; Peijnenburg, Willie J G M

2017-10-01

Singlet oxygen ( 1 O 2 ) can be photogenerated by photoactive xenobiotics and is capable of causing adverse effects due to its electrophilicity and its high reactivity with biological molecules. Detection of the production and distribution of 1 O 2 in living organisms is therefore of great importance. In this study, a luminescent probe ATTA-Eu 3+ combined with time-gated luminescence imaging was adopted to detect the distribution and temporal variation of 1 O 2 photoinduced by fluoroquinolone antibiotics and carboxylated/aminated graphenes in Daphnia magna. Results show that the xenobiotics generate 1 O 2 in living daphnids under simulated sunlight irradiation (SSR). The photogeneration of 1 O 2 by carboxylated/aminated graphenes was also confirmed by electron paramagnetic resonance spectroscopy. The strongest luminescence signals of 1 O 2 were observed in the hindgut of daphnids, and the signals in different areas of the daphnids (gut, thoracic legs and post-abdominal claw) displayed a similar trend of enhancement over irradiation time. Mean 1 O 2 concentrations at different regions of daphnids within one hour of SSR irradiation were estimated to be in the range of 0.5∼4.8μM. This study presented an efficient method for visualizing and quantifying the temporal and spatial distribution of 1 O 2 photogenerated by xenobiotics in living organisms, which can be employed for phototoxicity evaluation of xenobiotics. Copyright © 2017 Elsevier B.V. All rights reserved.

Photodegradation routes of the herbicide bromoxynil in solution and sorbed on silica nanoparticles.

PubMed

Escalada, Juan P; Arce, Valeria B; Carlos, Luciano; Porcal, Gabriela V; Biasutti, M Alicia; Criado, Susana; García, Norman A; Mártire, Daniel O

2014-04-01

Some organic contaminants dissolved in natural waters tend to adsorb on suspended particles and sediments. In order to mimic the photodegradation routes in natural waters of bromoxynil (BXN) adsorbed on silica, we here prepare and characterize silica nanoparticles modified with BXN (NP-BXN). We measure the direct photolysis quantum yield of aqueous BXN at 307 nm (0.064 ± 0.001) and detect the formation of bromide ions as a reaction product. Under similar conditions the photolysis quantum yield of BXN bonded to NP-BXN is much lower (0.0021 ± 0.0004) and does not lead to formation of bromide ions. The rate constant of the reaction of NP-BXN with the excited triplet states of riboflavin, a molecule employed as a proxy of chromophore dissolved organic matter (DOM) was measured in laser flash-photolysis experiments. The rate constants for the overall (kt) and chemical interaction (kr) of singlet oxygen with NP-BXN were also measured. Kinetic computer simulations show that the relevance of the direct and indirect (through reactions with reactive species generated in photoinduced processes) photodegradation routes of BXN is very much affected by sorption on silica. Immobilization of the herbicide on the particles, on one hand, affects the photolysis mechanism and lowers its photolysis quantum yield. On the other hand, the results obtained in aqueous suspensions indicate that immobilization also lowers the rate of collisional encounter, which affects the quenching rate constants of excited triplet states and singlet oxygen with the herbicide.

Photodynamic effects of 31 different phthalocyanines on a human keratinocyte cell line.

PubMed

Jančula, Daniel; Maršálek, Blahoslav; Babica, Pavel

2013-10-01

Phthalocyanines (Pcs, colored macromolecular compounds with the ability to generate singlet oxygen) represent a promising group of photosensitizers due to their intense absorption in the red and UV portion of the spectrum which leads to their excitation. In order to characterize possible toxic effects associated with eventual practical use and application of these chemicals, we employed an in vitro cell culture model to evaluate cytotoxic effects of 31 different phthalocyanines using neutral red uptake assay. An immortalized human keratinocyte cell line HaCaT was exposed to the tested chemicals for 2 or 24h, either with or without illumination in the last 60 min of the exposure period. After 2- or 24-h exposure without illumination, no cytotoxic effects or weak cytotoxic effects were induced by any Pc under the study and EC50 values could not be obtained within the tested concentration ranges (1.25-20 mg L(-1) or 0.625-10 mg L(-1)). On the other hand, exposure to phthalocyanines under illumination induced a significant cytotoxic effect. The most pronounced cytotoxicity was elicited by Pcs previously shown to have high positive charge densities at peripheral parts of substituent groups, which is most likely the factor responsible for the binding of Pc to negatively charged membranes on the cell surface and thus guaranteeing the tight connection necessary for the singlet oxygen attack on the cell surface. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of photodynamic activity, photostability and in vitro drug release of zinc phthalocyanine-loaded nanocapsules.

PubMed

de Souza, Thiane Deprá; Ziembowicz, Francieli Isa; Müller, Debora Friedrich; Lauermann, Sâmera Cristina; Kloster, Carmen Luisa; Santos, Roberto Christ Vianna; Lopes, Leonardo Quintana Soares; Ourique, Aline Ferreira; Machado, Giovanna; Villetti, Marcos Antonio

2016-02-15

Nanocapsule formulations containing zinc phthalocyanine (ZnPc) were investigated as drug delivery systems for use in photodynamic therapy (PDT). ZnPc loaded chitosan, PCL, and PCL coated with chitosan nanocapsules were prepared and characterized by means of their physicochemical properties, photodynamic activity, photostability and drug release profile. All formulations presented nanometric hydrodynamic radius, around 100 nm, low polydispersity index (0.08-0.24), slightly negative zeta potential for PCL nanoparticles and positive zeta potential for suspension containing chitosan. Encapsulation efficiencies were higher than 99%. The capacity of ZnPc loaded nanocapsules to produce cytotoxic singlet oxygen ((1)O2) by irradiation with red laser was monitored using 1.3-diphenylisobenzofuran as a probe. The singlet oxygen quantum yields (ΦΔ) for ZnPc loaded chitosan nanocapsules were high and similar to that of the standard (ZnPc in DMSO), displaying excellent ability to generate (1)O2. The photosensitizer loaded nanocapsules are photostable in the timescale usually utilized in PDT and only a small photobleaching event was observed when a light dose of 610J/cm(2) was applied. The in vitro drug release studies of ZnPc from all nanocapsules demonstrated a sustained release profile controlled by diffusion, without burst effect. The nature of the polymer and the core type of the nanocapsules regulated ZnPc release. Thus, the nanocapsules developed in this work are a promising strategy to be employed in PDT. Copyright © 2015. Published by Elsevier B.V.

Towards cancer cell-specific phototoxic organometallic rhenium(I) complexes.

PubMed

Leonidova, Anna; Pierroz, Vanessa; Rubbiani, Riccardo; Heier, Jakob; Ferrari, Stefano; Gasser, Gilles

2014-03-21

Over the recent years, several Re(I) organometallic compounds have been shown to be toxic to various cancer cell lines. However, these compounds lacked sufficient selectivity towards cancer tissues to be used as novel chemotherapeutic agents. In this study, we probe the potential of two known N,N-bis(quinolinoyl) Re(I) tricarbonyl complex derivatives, namely Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-4-butane-1-amine (Re-NH₂) and Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-5-valeric acid (Re-COOH), as photodynamic therapy (PDT) photosensitizers. Re-NH₂ and Re-COOH proved to be excellent singlet oxygen generators in a lipophilic environment with quantum yields of about 75%. Furthermore, we envisaged to improve the selectivity of Re-COOH via conjugation to two types of peptides, namely a nuclear localization signal (NLS) and a derivative of the neuropeptide bombesin, to form Re-NLS and Re-Bombesin, respectively. Fluorescent microscopy on cervical cancer cells (HeLa) showed that the conjugation of Re-COOH to NLS significantly enhanced the compound's accumulation into the cell nucleus and more specifically into its nucleoli. Importantly, in view of PDT applications, the cytotoxicity of the Re complexes and their bioconjugates increased significantly upon light irradiation. In particular, Re-Bombesin was found to be at least 20-fold more toxic after light irradiation. DNA photo-cleavage studies demonstrated that all compounds damaged DNA via singlet oxygen and, to a minor extent, superoxide production.

Stimuli-responsive magnetic nanoparticles for tumor-targeted bimodal imaging and photodynamic/hyperthermia combination therapy

NASA Astrophysics Data System (ADS)

Kim, Kyoung Sub; Kim, Jiyoung; Lee, Joo Young; Matsuda, Shofu; Hideshima, Sho; Mori, Yasurou; Osaka, Tetsuya; Na, Kun

2016-06-01

Despite magnetic nanoparticles having shown great potential in cancer treatment, tremendous challenges related to diagnostic sensitivity and treatment efficacy for clinical application remain. Herein, we designed optimized multifunctional magnetite nanoparticles (AHP@MNPs), composed of Fe3O4 nanoparticles and photosensitizer conjugated hyaluronic acid (AHP), to achieve enhanced tumor diagnosis and therapy. Fe3O4 nanoparticles (MNPs) were synthesized by a facile hydrolysis method. MNPs have higher biocompatibility, controllable particle sizes, and desirable magnetic properties. The fabricated AHP@MNPs have enhanced water solubility (average size: 108.13 +/- 1.08 nm), heat generation properties, and singlet oxygen generation properties upon magnetic and laser irradiation. The AHP@MNPs can target tumors via CD44 receptor-mediated endocytosis, which have enhanced tumor therapeutic effects through photodynamic/hyperthermia-combined treatment without any drugs. We successfully detected tumors implanted in mice via magnetic resonance imaging and optical imaging. Furthermore, we demonstrated the photodynamic/hyperthermia-combined therapeutic efficacy of AHP@MNPs with synergistically enhanced efficacy against cancer.Despite magnetic nanoparticles having shown great potential in cancer treatment, tremendous challenges related to diagnostic sensitivity and treatment efficacy for clinical application remain. Herein, we designed optimized multifunctional magnetite nanoparticles (AHP@MNPs), composed of Fe3O4 nanoparticles and photosensitizer conjugated hyaluronic acid (AHP), to achieve enhanced tumor diagnosis and therapy. Fe3O4 nanoparticles (MNPs) were synthesized by a facile hydrolysis method. MNPs have higher biocompatibility, controllable particle sizes, and desirable magnetic properties. The fabricated AHP@MNPs have enhanced water solubility (average size: 108.13 +/- 1.08 nm), heat generation properties, and singlet oxygen generation properties upon magnetic and laser irradiation. The AHP@MNPs can target tumors via CD44 receptor-mediated endocytosis, which have enhanced tumor therapeutic effects through photodynamic/hyperthermia-combined treatment without any drugs. We successfully detected tumors implanted in mice via magnetic resonance imaging and optical imaging. Furthermore, we demonstrated the photodynamic/hyperthermia-combined therapeutic efficacy of AHP@MNPs with synergistically enhanced efficacy against cancer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02273a

LASERS IN MEDICINE: Quantum efficiency of the laser-excited singlet-oxygen-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine

NASA Astrophysics Data System (ADS)

Bashtanov, M. E.; Drozdova, N. N.; Krasnovskii, A. A.

1999-12-01

An investigation was made of the ratios of the intensity Idf of the singlet-oxygen(1O2)-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine (ZnTBPc), with the maximum at λ = 685 nm, to the intensity I1270 of the photosensitised phosphorescence of 1O2 with the maximum at λ = 1270 nm in deuterated benzene when excited with λ = 337 nm nitrogen-laser pulses. Depending on the energy density of the laser radiation (0.25 — 0.7 mJ cm-2) and on the concentration of ZnTBPc (0.06 — 3.4 μM), the ratio of the zero-time intensities of the delayed fluorescence of ZnTBPc and of the singlet-oxygen phosphorescence Idf0/I12700 varied from 0.01 to 0.2 in air-saturated solutions of ZnTBPc. The intensity Idf0 decreased fivefold as a result of saturation with oxygen of air-saturated solutions. The quantum efficiency of the delayed fluorescence was represented by the coefficient α =(Idf0/I12700)kr/(γf[1O2]0[ZnTBPc]), where [1O2]0 is the zero-time concentration of 1O2 after a laser shot; kr is the rate constant of radiative deactivation of 1O2 in the investigated solvent; γf is the quantum yield of the ZnTBPc fluorescence. It was established that in the case of air-saturated solutions of ZnTBPc this coefficient was approximately 200 times less than for metal-free tetra(4-tert-butyl)phthalocyanine and its absolute value was ~2 × 1011 M-2 s-1.

Continuous Photo-Oxidation in a Vortex Reactor: Efficient Operations Using Air Drawn from the Laboratory

PubMed Central

2017-01-01

We report the construction and use of a vortex reactor which uses a rapidly rotating cylinder to generate Taylor vortices for continuous flow thermal and photochemical reactions. The reactor is designed to operate under conditions required for vortex generation. The flow pattern of the vortices has been represented using computational fluid dynamics, and the presence of the vortices can be easily visualized by observing streams of bubbles within the reactor. This approach presents certain advantages for reactions with added gases. For reactions with oxygen, the reactor offers an alternative to traditional setups as it efficiently draws in air from the lab without the need specifically to pressurize with oxygen. The rapid mixing generated by the vortices enables rapid mass transfer between the gas and the liquid phases allowing for a high efficiency dissolution of gases. The reactor has been applied to several photochemical reactions involving singlet oxygen (1O2) including the photo-oxidations of α-terpinene and furfuryl alcohol and the photodeborylation of phenyl boronic acid. The rotation speed of the cylinder proved to be key for reaction efficiency, and in the operation we found that the uptake of air was highest at 4000 rpm. The reactor has also been successfully applied to the synthesis of artemisinin, a potent antimalarial compound; and this three-step synthesis involving a Schenk-ene reaction with 1O2, Hock cleavage with H+, and an oxidative cyclization cascade with triplet oxygen (3O2), from dihydroartemisinic acid was carried out as a single process in the vortex reactor. PMID:28781513

Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

DOE PAGES

Pace, Natalie A.; Zhang, Weimin; Arias, Dylan H.; ...

2017-11-30

The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. We investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side-chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically and is strongly dependent on side-chain identity. These results show that it may be necessary to carefullymore » engineer the solid-state microstructure of these 'singlet fission polymers' to produce the long-lived triplets needed to realize efficient photovoltaic devices.« less

Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, Natalie A.; Zhang, Weimin; Arias, Dylan H.

The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. We investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side-chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically and is strongly dependent on side-chain identity. These results show that it may be necessary to carefullymore » engineer the solid-state microstructure of these 'singlet fission polymers' to produce the long-lived triplets needed to realize efficient photovoltaic devices.« less

Unified model for singlet fission within a non-conjugated covalent pentacene dimer

NASA Astrophysics Data System (ADS)

Basel, Bettina S.; Zirzlmeier, Johannes; Hetzer, Constantin; Phelan, Brian T.; Krzyaniak, Matthew D.; Reddy, S. Rajagopala; Coto, Pedro B.; Horwitz, Noah E.; Young, Ryan M.; White, Fraser J.; Hampel, Frank; Clark, Timothy; Thoss, Michael; Tykwinski, Rik R.; Wasielewski, Michael R.; Guldi, Dirk M.

2017-05-01

When molecular dimers, crystalline films or molecular aggregates absorb a photon to produce a singlet exciton, spin-allowed singlet fission may produce two triplet excitons that can be used to generate two electron-hole pairs, leading to a predicted ~50% enhancement in maximum solar cell performance. The singlet fission mechanism is still not well understood. Here we report on the use of time-resolved optical and electron paramagnetic resonance spectroscopy to probe singlet fission in a pentacene dimer linked by a non-conjugated spacer. We observe the key intermediates in the singlet fission process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons. Using these combined data, we develop a single kinetic model that describes the data over seven temporal orders of magnitude both at room and cryogenic temperatures.

Unified model for singlet fission within a non-conjugated covalent pentacene dimer.

PubMed

Basel, Bettina S; Zirzlmeier, Johannes; Hetzer, Constantin; Phelan, Brian T; Krzyaniak, Matthew D; Reddy, S Rajagopala; Coto, Pedro B; Horwitz, Noah E; Young, Ryan M; White, Fraser J; Hampel, Frank; Clark, Timothy; Thoss, Michael; Tykwinski, Rik R; Wasielewski, Michael R; Guldi, Dirk M

2017-05-18

When molecular dimers, crystalline films or molecular aggregates absorb a photon to produce a singlet exciton, spin-allowed singlet fission may produce two triplet excitons that can be used to generate two electron-hole pairs, leading to a predicted ∼50% enhancement in maximum solar cell performance. The singlet fission mechanism is still not well understood. Here we report on the use of time-resolved optical and electron paramagnetic resonance spectroscopy to probe singlet fission in a pentacene dimer linked by a non-conjugated spacer. We observe the key intermediates in the singlet fission process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons. Using these combined data, we develop a single kinetic model that describes the data over seven temporal orders of magnitude both at room and cryogenic temperatures.

Photophysicochemical behaviour and antimicrobial properties of monocarboxy Mg (II) and Al (III) phthalocyanine-magnetite conjugates

NASA Astrophysics Data System (ADS)

Idowu, Mopelola Abidemi; Xego, Solami; Arslanoglu, Yasin; Mark, John; Antunes, Edith; Nyokong, Tebello

2018-03-01

Asymmetric Mg (II) or Al (III) phthalocyanine (containing a COOH group and 3-pyridylsulfanyl units) was conjugated via an amide bond to amino functionalized magnetic nanoparticle (AIMN) to form MgPc-AIMN or AlPc-AIMN conjugate, and characterized. The photophysicochemical behaviour of the phthalocyanine-AIMN conjugates was investigated and compared to the asymmetric Pcs and to the simple mixture of Pc with AIMNs without a chemical bond, (MPc-AIMN (mixed)). The directed covalent linkage of AIMNs to the asymmetrical metallopthalocyanines afforded improvements in the singlet oxygen (VΔ) and triplet state quantum yield (VT) as well as singlet oxygen lifetimes for the MPcs-AIMN-linked conjugates compared to MPc-AIMN (mixed) and MPcs alone. The asymmetric phthalocyanines and their conjugates showed effective antimicrobial activity against Escherichia coli bacteria under illumination.

Singlet exciton fission photovoltaics.

PubMed

Lee, Jiye; Jadhav, Priya; Reusswig, Philip D; Yost, Shane R; Thompson, Nicholas J; Congreve, Daniel N; Hontz, Eric; Van Voorhis, Troy; Baldo, Marc A

2013-06-18

Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption.

Flavor-singlet spectrum in multi-flavor QCD

NASA Astrophysics Data System (ADS)

Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed; Kurachi, Masafumi; Maskawa, Toshihide; Miura, Kohtaroh; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

2018-03-01

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

Flavor-singlet spectrum in multi-flavor QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Yasamichi; Rinaldi, Enrico

2017-06-18

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixedmore » number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.« less

Electron Transfer from Triplet State of TIPS-Pentacene Generated by Singlet Fission Processes to CH3NH3PbI3 Perovskite.

PubMed

Lee, Sangsu; Hwang, Daesub; Jung, Seok Il; Kim, Dongho

2017-02-16

To reveal the applicability of singlet fission processes in perovskite solar cell, we investigated electron transfer from TIPS-pentacene to CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite in film phase. Through the observation of the shorter fluorescence lifetime in TIPS-pentacene/MAPbI 3 perovskite bilayer film (5 ns) compared with pristine MAPbI 3 perovskite film (20 ns), we verified electron-transfer processes between TIPS-pentacene and MAPbI 3 perovskite. Furthermore, the observation of singlet fission processes, a faster decay rate, TIPS-pentacene cations, and the analysis of kinetic profiles of the intensity ratio between 500 and 525 nm in the TA spectra of the TIPS-pentacene/MAPbI 3 perovskite bilayer film indicate that electron transfer occurs from triplet state of TIPS-pentacene generated by singlet fission processes to MAPbI 3 perovskite conduction band. We believe that our results can provide useful information on the design of solar cells sensitized by singlet fission processes and pave the way for new types of perovskite solar cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, S.; Lewis, I. M.

One of the simplest extensions of the Standard Model (SM) is the addition of a scalar gauge singlet, S . If S is not forbidden by a symmetry from mixing with the Standard Model Higgs boson, the mixing will generate non-SM rates for Higgs production and decays. Generally, there could also be unknown high energy physics that generates additional effective low energy interactions. We show that interference effects between the scalar resonance of the singlet model and the effective field theory (EFT) operators can have significant effects in the Higgs sector. Here, we examine a non- Z 2 symmetricmore » scalar singlet model and demonstrate that a fit to the 125 GeV Higgs boson couplings and to limits on high mass resonances, S , exhibit an interesting structure and possible large cancellations of effects between the resonance contribution and the new EFT interactions, that invalidate conclusions based on the renormalizable singlet model alone.« less

Green oxidations of furans--initiated by molecular oxygen--that give key natural product motifs.

PubMed

Montagnon, Tamsyn; Noutsias, Dimitris; Alexopoulou, Ioanna; Tofi, Maria; Vassilikogiannakis, Georgios

2011-04-07

In this article, we explore how changes in the positioning of pendant hydroxyl functionalities in the photooxygenation substrate dramatically alter the course of furan oxidations that are initiated by singlet oxygen; and, how these different reactivities can be harnessed through cascade reaction sequences to access, rapidly and effectively, a broad range of important natural product motifs.

Global potential energy surface of ground state singlet spin O4

NASA Astrophysics Data System (ADS)

Mankodi, Tapan K.; Bhandarkar, Upendra V.; Puranik, Bhalchandra P.

2018-02-01

A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2-O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.

The role of reactive oxygen species in the degradation of lignin derived dissolved organic matter

NASA Astrophysics Data System (ADS)

Waggoner, Derek C.; Wozniak, Andrew S.; Cory, Rose M.; Hatcher, Patrick G.

2017-07-01

Evidence suggests that reactive oxygen species (ROS) are important in transforming the chemical composition of the large pool of terrestrially-derived dissolved organic matter (DOM) exported from land to water annually. However, due to the challenges inherent in isolating the effects of individual ROS on DOM composition, the role of ROS in the photochemical alteration of DOM remains poorly characterized. In this work, terrestrial DOM was independently exposed to singlet oxygen (1O2), and superoxide (O2-rad under controlled laboratory conditions). Using ultra-high resolution mass spectrometry to track molecular level alterations of DOM by ROS, these findings suggest exposure to 1O2 (generated using Rose Bengal and visible light) removed formulas with an O/C > 0.3, and primarily resulted in DOM comprised of formulas with higher oxygen content, while O2-rad exposure (from KO2 in DMSO) removed formulas with O/C < 0.3 and produced aliphatic formulas (H/C > 1.5). Comparison of DOM altered by ROS in this study to riverine and coastal DOM showed that (20-80%) overlap in formulas, providing evidence for the role of ROS in shaping the composition of DOM exported from rivers to oceans.

Convergence of the transcriptional responses to heat shock and singlet oxygen stresses.

PubMed

Dufour, Yann S; Imam, Saheed; Koo, Byoung-Mo; Green, Heather A; Donohue, Timothy J

2012-09-01

Cells often mount transcriptional responses and activate specific sets of genes in response to stress-inducing signals such as heat or reactive oxygen species. Transcription factors in the RpoH family of bacterial alternative σ factors usually control gene expression during a heat shock response. Interestingly, several α-proteobacteria possess two or more paralogs of RpoH, suggesting some functional distinction. We investigated the target promoters of Rhodobacter sphaeroides RpoH(I) and RpoH(II) using genome-scale data derived from gene expression profiling and the direct interactions of each protein with DNA in vivo. We found that the RpoH(I) and RpoH(II) regulons have both distinct and overlapping gene sets. We predicted DNA sequence elements that dictate promoter recognition specificity by each RpoH paralog. We found that several bases in the highly conserved TTG in the -35 element are important for activity with both RpoH homologs; that the T-9 position, which is over-represented in the RpoH(I) promoter sequence logo, is critical for RpoH(I)-dependent transcription; and that several bases in the predicted -10 element were important for activity with either RpoH(II) or both RpoH homologs. Genes that are transcribed by both RpoH(I) and RpoH(II) are predicted to encode for functions involved in general cell maintenance. The functions specific to the RpoH(I) regulon are associated with a classic heat shock response, while those specific to RpoH(II) are associated with the response to the reactive oxygen species, singlet oxygen. We propose that a gene duplication event followed by changes in promoter recognition by RpoH(I) and RpoH(II) allowed convergence of the transcriptional responses to heat and singlet oxygen stress in R. sphaeroides and possibly other bacteria.

In vivo selective cancer-tracking gadolinium eradicator as new-generation photodynamic therapy agent

PubMed Central

Zhang, Tao; Lan, Rongfeng; Chan, Chi-Fai; Law, Ga-Lai; Wong, Wai-Kwok; Wong, Ka-Leung

2014-01-01

In this work, we demonstrate a modality of photodynamic therapy (PDT) through the design of our truly dual-functional—PDT and imaging—gadolinium complex (Gd-N), which can target cancer cells specifically. In the light of our design, the PDT drug can specifically localize on the anionic cell membrane of cancer cells in which its laser-excited photoemission signal can be monitored without triggering the phototoxic generation of reactive oxygen species—singlet oxygen—before due excitation. Comprehensive in vitro and in vivo studies had been conducted for the substantiation of the effectiveness of Gd-N as such a tumor-selective PDT photosensitizer. This treatment modality does initiate a new direction in the development of “precision medicine” in line with stem cell and gene therapies as tools in cancer therapy. PMID:25453097

Nanoparticles with Embedded Porphyrin Photosensitizers for Photooxidation Reactions and Continuous Oxygen Sensing.

PubMed

Kubát, Pavel; Henke, Petr; Berzediová, Veronika; Štěpánek, Miroslav; Lang, Kamil; Mosinger, Jiří

2017-10-18

We report the synthesis and characterization of sulfonated polystyrene nanoparticles (average diameter 30 ± 14 nm) with encapsulated 5,10,15,20-tetraphenylporphyrin or ionically entangled tetracationic 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin, their photooxidation properties, and the application of singlet oxygen-sensitized delayed fluorescence (SODF) in oxygen sensing. Both types of nanoparticles effectively photogenerated singlet oxygen, O 2 ( 1 Δ g ). The O 2 ( 1 Δ g ) phosphorescence, transient absorption of the porphyrin triplet states, and SODF signals were monitored using time-resolved spectroscopic techniques. The SODF intensity depended on the concentration of the porphyrin photosensitizer and dissolved oxygen and on the temperature. After an initial period (a few microseconds), the kinetics of the SODF process can be approximated as a monoexponential function, and the apparent SODF lifetimes can be correlated with the oxygen concentration. The oxygen sensing based on SODF allowed measurement of the dissolved oxygen in aqueous media in the broad range of oxygen concentrations (0.2-38 mg L -1 ). The ability of both types of nanoparticles to photooxidize external substrates was predicted by the SODF measurements and proven by chemical tests. The relative photooxidation efficacy was highest at a low porphyrin concentration, as indicated by the highest fluorescence quantum yield (Φ F ), and it corresponds with negligible inner filter and self-quenching effects. The photooxidation abilities were sensitive to the influence of temperature on the diffusion and solubility of oxygen in both polystyrene and water media and to the rate constant of the O 2 ( 1 Δ g ) reaction with a substrate. Due to their efficient photogeneration of cytotoxic O 2 ( 1 Δ g ) at physiological temperatures and their oxygen sensing via SODF, both types of nanoparticles are promising candidates for biomedical applications.

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

DOE PAGES

Ho, Junming; Kish, Elizabeth; Méndez-Hernandez, Dalvin D.; ...

2017-06-26

In photosynthetic organisms, protection against photo-oxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll to carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, while it is ultrafast in the oxygen-rich chloroplasts of oxygen evolving photosynthetic organisms. In order to better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomericmore » carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET including a resonance Raman based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by DFT calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). In conclusion, both DFT and EPR analysis further indicates that upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.« less

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Junming; Kish, Elizabeth; Méndez-Hernandez, Dalvin D.

In photosynthetic organisms, protection against photo-oxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll to carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, while it is ultrafast in the oxygen-rich chloroplasts of oxygen evolving photosynthetic organisms. In order to better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomericmore » carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET including a resonance Raman based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by DFT calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). In conclusion, both DFT and EPR analysis further indicates that upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.« less

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

PubMed Central

Ho, Junming; Kish, Elizabeth; Méndez-Hernández, Dalvin D.; WongCarter, Katherine; Pillai, Smitha; Kodis, Gerdenis; Niklas, Jens; Poluektov, Oleg G.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.; Batista, Victor S.

2017-01-01

In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet–triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads. PMID:28652359

Mechanisms of tumor destruction caused by photodynamic therapy

NASA Astrophysics Data System (ADS)

Zhou, Chuannong

2005-07-01

Photodynamic therapy is a relatively new treatment modality and is becoming widely accepted as a standard treatment of a variety of solid tumors. This includes palliative treatments for advanced or obstructive cancers in many organs as well as a curative treatment for some early cancers and pre-cancerous lesions. It has been approved by health authorities in a number of countries in America, Europe and Asia [1]. PDT is a procedure requiring 3 elements: photosensitizer, light and oxygen [2]. The typical technique involves an intravenous administration of a photosensitizing agent, which is preferentially accumulated or retained in tumor tissue, followed by irradiation of the tumor area with light of appropriate wavelength. In the presence of oxygen it generates highly reactive and cytotoxic molecular species, in particular, singlet oxygen (1O2), which may oxidize various bio-molecules and finally leading to cell death and tumor destruction [3]. The most widely used photosensitizer in clinical treatment of cancers is Photofrin (porfimer sodium), and most widely used light sources are lasers of various types, in recent years preferentially, diode laser, which emits a red light of 630 nm wavelength.

Diphotons from electroweak triplet-singlet mixing

DOE PAGES

Howe, Kiel; Knapen, Simon; Robinson, Dean J.

2016-08-23

The neutral component of a real pseudoscalar electroweak (EW) triplet can produce a diphoton excess at 750 GeV, if it is somewhat mixed with an EW singlet pseudoscalar. This triplet-singlet mixing allows for greater freedom in the diboson branching ratios than the singlet-only case, but it is still possible to probe the parameter space extensively with 300 fb -1. The charged component of the triplet is pair produced at the LHC, which results in a striking signal in the form of a pair of Wγ resonances with an irreducible rate of 0.27 fb. Other signatures include multiboson final states from cascade decaysmore » of the triplet-singlet neutral states. In conclusion, a large class of composite models feature both EW singlet and triplet pseudo-Nambu-Goldstone bosons in their spectrum, with the diboson couplings generated by axial anomalies.« less

Unified model for singlet fission within a non-conjugated covalent pentacene dimer

DOE PAGES

Basel, Bettina S.; Zirzlmeier, Johannes; Hetzer, Constantin; ...

2017-05-18

When molecular dimers, crystalline films or molecular aggregates absorb a photon to produce a singlet exciton, spin-allowed singlet fission may produce two triplet excitons that can be used to generate two electron–hole pairs, leading to a predicted B50% enhancement in maximum solar cell performance. The singlet fission mechanism is still not well understood. Here we report on the use of time-resolved optical and electron paramagnetic resonance spectroscopy to probe singlet fission in a pentacene dimer linked by a non-conjugated spacer. We observe the key intermediates in the singlet fission process, including the formation and decay of a quintet state thatmore » precedes formation of the pentacene triplet excitons. In conclusion, using these combined data, we develop a single kinetic model that describes the data over seven temporal orders of magnitude both at room and cryogenic temperatures.« less

Unified model for singlet fission within a non-conjugated covalent pentacene dimer

PubMed Central

Basel, Bettina S.; Zirzlmeier, Johannes; Hetzer, Constantin; Phelan, Brian T.; Krzyaniak, Matthew D.; Reddy, S. Rajagopala; Coto, Pedro B.; Horwitz, Noah E.; Young, Ryan M.; White, Fraser J.; Hampel, Frank; Clark, Timothy; Thoss, Michael; Tykwinski, Rik R.; Wasielewski, Michael R.; Guldi, Dirk M.

2017-01-01

When molecular dimers, crystalline films or molecular aggregates absorb a photon to produce a singlet exciton, spin-allowed singlet fission may produce two triplet excitons that can be used to generate two electron–hole pairs, leading to a predicted ∼50% enhancement in maximum solar cell performance. The singlet fission mechanism is still not well understood. Here we report on the use of time-resolved optical and electron paramagnetic resonance spectroscopy to probe singlet fission in a pentacene dimer linked by a non-conjugated spacer. We observe the key intermediates in the singlet fission process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons. Using these combined data, we develop a single kinetic model that describes the data over seven temporal orders of magnitude both at room and cryogenic temperatures. PMID:28516916

Photodegradation of naproxen and its photoproducts in aqueous solution at 254 nm: a kinetic investigation.

PubMed

Marotta, Raffaele; Spasiano, Danilo; Di Somma, Ilaria; Andreozzi, Roberto

2013-01-01

The kinetics of photodegradation of the non steroidal anti-inflammatory drug naproxen (+)-S-2-(6-methoxynaphthalen-2-yl)propanoic acid, an emerging organic pollutant, was studied in aqueous solutions under deaerated and aerated conditions. The photolysis experiments were carried out under monochromatic irradiation (λ = 254 nm) at pH = 7.0 and T = 25 °C. Simplified reaction schemes of photodegradation of naproxen are proposed in absence and in presence of oxygen respectively. The schemes take into account the photolysis of naproxen and its photoproducts and the reactions of the measured species with oxygen dissolved in the liquid bulk. According to these schemes, two kinetic models were developed which correlate the experimental data, for runs performed in absence and in presence of oxygen, with a fair accuracy and allowed to estimate the best values for the unknown kinetic parameters. The calculated quantum yield of direct photolysis of naproxen under deaerated media is in good agreement with the one previously reported. Under aerated conditions, the generation of singlet oxygen has also been taken into account. The obtained results, under the adopted conditions, indicated a marked influence of dissolved oxygen on the photodegradation rates of naproxen and the relative distribution of the major reaction intermediates. Copyright © 2012 Elsevier Ltd. All rights reserved.

Diketopyrrolopyrrole-based carbon dots for photodynamic therapy.

PubMed

He, Haozhe; Zheng, Xiaohua; Liu, Shi; Zheng, Min; Xie, Zhigang; Wang, Yong; Yu, Meng; Shuai, Xintao

2018-06-01

The development of a simple and straightforward strategy to synthesize multifunctional carbon dots for photodynamic therapy (PDT) has been an emerging focus. In this work, diketopyrrolopyrrole-based fluorescent carbon dots (DPP CDs) were designed and synthesized through a facile one-pot hydrothermal method by using diketopyrrolopyrrole (DPP) and chitosan (CTS) as raw materials. DPP CDs not only maintained the ability of DPP to generate singlet oxygen (1O2) but also have excellent hydrophilic properties and outstanding biocompatibility. In vitro and in vivo experiments demonstrated that DPP CDs greatly inhibited the growth of tumor cells under laser irradiation (540 nm). This study highlights the potential of the rational design of CDs for efficient cancer therapy.

Photodamage of the cells in culture sensitized with bilirubin

NASA Astrophysics Data System (ADS)

Kozlenkova, O. A.; Plavskaya, L. G.; Mikulich, A. V.; Leusenko, I. A.; Tretyakova, A. I.; Plavskii, V. Yu

2016-08-01

It has been shown that exposure to radiation of LED sources of light with an emission band maximum at about 465 and 520 nm having substantially identical damaging effects on animal cells in culture, that are in a logarithmic growth phase and preincubated with pigment. Photobiological effect is caused by photodynamic processes involving singlet oxygen generated by triplet excited sensitizer. Mono-exponential type dependence of cell survival on the energy dose indicates that it is bilirubin that acts as a sensitizer but not its photoproducts. The inclusion of bilirubin in the cells, where it is primarily localized in the mitochondria cells, it is accompanied by multiple amplification photochemical stability compared to pigment molecules bound with albumin

The phototoxicity of phenothiazinium derivatives against Escherichia coli and Staphylococcus aureus.

PubMed

Phoenix, D A; Sayed, Z; Hussain, S; Harris, F; Wainwright, M

2003-10-24

Phenothiazinium dyes, and derivatives, were tested for toxicity to Escherichia coli and Staphylococcus aureus. The dyes were generally lipophilic (log P>1) and showed inherent dark toxicity (minimum lethal concentrations: 3.1-1000 microM). Dye illumination (total light dose of 3.15 J cm(-1) over 30 min) led to up to eight-fold reductions in minimum lethal concentrations. Most of the illuminated dyes showed significant relative singlet oxygen yields (phi'delta: 0.18-1.35) suggesting a type II mechanism of generating a phototoxic response. Although generally up to six-fold more effective against S. aureus, the dyes tested efficiently killed E. coli and may be of particular use in combating Gram-negative pathogens.

Photochemistry and photooxidation of tetraphenyl-p-dioxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, M.V.; Kumar, C.V.; Scaiano, J.C.

1979-09-20

Laser flash photolysis studies of tetraphenyl-p-dioxin have led to the characterization of its triplet state. The T-T absorption spectra shows maxima at 350 and 545 nm; the triplet has a lifetime of 535 ns in methanol and can be quenched by di-tert-butyl nitroxide, paraquat dications, oxygen, and di-tert-butyl selenoketone. The interaction of the triplet with oxygen leads to the formation of singlet oxygen which in turn reacts with the title compound to yield benzil.

Research on the effect of formononetin on photodynamic therapy in K562 cells.

PubMed

Sun, Dan; Lu, Yao; Zhang, Su-Juan; Wang, Kai-Ge; Sun, Zhe

2017-10-01

At the present time, many cancer patients combine some forms of complementary and alternative medicine therapies with their conventional therapies. The most common choice of these therapies is the use of antioxidants. Formononetin is presented in different foods. It has a variety of biological activities including antioxidant and anti-cancer properties. On account of its antioxidant activity, formononetin might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species (ROS) production was stimulated leading to irreversible tumor cell injury. In this study, the influence of formononetin on K562 cells in PDT was demonstrated. The results showed that formononetin supplementation alone did not affect the lipid peroxidation, DNA damage and apoptosis in K562 cells. It increases the lipid peroxidation, DNA damage and apoptosis in K562 cells induced by PDT. The singlet oxygen quencher sodium azide suppresses the apoptosis induced by PDT with formononetin. In conclusion, formononetin consumption during PDT increases the effectiveness of cancer therapy on malignant cells. The effect of antioxidants on PDT maybe was determined by its sensitization ability to singlet oxygen.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ames, B.N.; Cathcart, R.; Schwiers, E.

During primate evolution, a major factor in lengthening life-span and decreasing age-specific cancer rates may have been improved protective mechanisms against oxygen radicals. We propose that one of these protective systems is plasma uric acid, the level of which increased markedly during primate evolution as a consequence of a series of mutations. Uric acid is a powerful antioxidant and is a scavenger of singlet oxygen and radicals. We show that, at physiological concentrations, urate reduces the oxo-heme oxidant formed by peroxide reaction with hemoglobin, protects erythrocyte ghosts against lipid peroxidation, and protects erythrocytes from peroxidative damage leading to lysis. Uratemore » is about as effective an antioxidant as ascorbate in these experiments. Urate is much more easily oxidized than deoxynucleosides by singlet oxygen and is destroyed by hydroxyl radicals at a comparable rate. The plasma urate level in humans (about 300 ..mu..M) is considerably higher than the ascorbate level, making it one of the major antioxidants in humans. Previous work on urate reported in the literature supports our experiments and interpretations, although the findings were not discussed in a physiological context.« less

Synthesis and Spectral Evaluation of Some Unsymmetrical Mesoporphyrinic Complexes

PubMed Central

Boscencu, Rica; Oliveira, Anabela Sousa; Ferreira, Diana P.; Ferreira, Luís Filipe Vieira

2012-01-01

Synthesis and spectral evaluation of new zinc and copper unsymmetrical mesoporphyrinic complexes are reported. Zn(II)-5-(4-acetoxy-3-methoxyphenyl)-10,15,20- tris-(4-carboxymethylphenyl)porphyrin, Zn(II)-5-[(3,4-methylenedioxy)phenyl]-10,15,20- tris-(4-carboxymethylphenyl)porphyrin, Cu(II)-5-(4-acetoxy-3-methoxyphenyl)-10,15,20- tris-(4-carboxymethylphenyl)porphyrin and Cu(II)-5-[(3,4-methylenedioxy)phenyl]-10,15,20- tris-(4-carboxymethylphenyl)porphyrin were synthesized using microwave-assisted synthesis. The complexes were characterized by elemental analysis, FT-IR, UV-Vis, EPR and NMR spectroscopy, which fully confirmed their structure. The spectral absorption properties of the porphyrinic complexes were studied in solvents with different polarities. Fluorescence emission and singlet oxygen formation quantum yields were evaluated for the compounds under study, revealing high yields for the zinc derivatives. The copper complexes are not emissive and only display residual capacity for singlet oxygen formation. PMID:22942693

Factors influencing the regioselectivity of the oxidation of asymmetric secondary amines with singlet oxygen.

PubMed

Ushakov, Dmitry B; Plutschack, Matthew B; Gilmore, Kerry; Seeberger, Peter H

2015-04-20

Aerobic amine oxidation is an attractive and elegant process for the α functionalization of amines. However, there are still several mechanistic uncertainties, particularly the factors governing the regioselectivity of the oxidation of asymmetric secondary amines and the oxidation rates of mixed primary amines. Herein, it is reported that singlet-oxygen-mediated oxidation of 1° and 2° amines is sensitive to the strength of the α-C-H bond and steric factors. Estimation of the relative bond dissociation energy by natural bond order analysis or by means of one-bond C-H coupling constants allowed the regioselectivity of secondary amine oxidations to be explained and predicted. In addition, the findings were utilized to synthesize highly regioselective substrates and perform selective amine cross-couplings to produce imines. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Singlet oxygen quenching and radical scavenging capacities of structurally-related flavonoids present in Zuccagnia punctata Cav.

PubMed

Vieyra, Faustino E Morán; Boggetti, Héctor J; Zampini, Iris C; Ordoñez, Roxana M; Isla, María I; Alvarez, Rosa M S; De Rosso, Veridiana; Mercadante, Adriana Z; Borsarelli, Claudio D

2009-06-01

The singlet oxygen (1O2) quenching and free radical (DPPH(*), ABTS(* +) and O2(* -)) scavenging ability of three structurally-related flavonoids (7-hydroxyflavanone HF, 2',4'-dihydroxychalcone DHC and 3,7-dihydroxyflavone DHF) present in the Argentinean native shrub Zuccagnia punctata Cav. were studied in solution by combining electrochemical and kinetic measurements, mass spectroscopy, end-point antioxidant assays and computational calculations. The results showed that the antioxidant properties of these flavonoids depend on several factors, such as their electron- and hydrogen atom donor capacity, the ionization degree of the more acidic group, solvatation effects and electrostatic interactions with the oxidant species. The theoretical calculations for both the gas and solution phases at the B3LYP level of theory for the Osanger reaction field model agreed with the experimental findings, thus supporting the characterization of the antioxidant mechanism of the Z. punctata flavonoids.