Photochemistry and Photobiology

Cover image for Vol. 90 Issue 5

Edited By: Jean Cadet

Impact Factor: 2.684

ISI Journal Citation Reports © Ranking: 2013: 36/74 (Biophysics); 161/291 (Biochemistry & Molecular Biology)

Online ISSN: 1751-1097

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  • RESEARCH ARTICLE: “Pointsource” Delivery of a Photosensitizer Drug and Singlet Oxygen: Eradication of Glioma Cells In Vitro

    RESEARCH ARTICLE: “Pointsource” Delivery of a Photosensitizer Drug and Singlet Oxygen: Eradication of Glioma Cells In Vitro

    We describe a pointsource sensitizer-tipped microoptic device for the eradication of glioma U87 cells. The device has a mesoporous fluorinated silica tip which emits singlet oxygen molecules and small quantities of pheophorbide sensitizer for additional production of singlet oxygen in the immediate vicinity. The results show that the device surges in sensitizer release and photokilling with higher rates about midway through the reaction. This was attributed to a self-amplified autocatalytic reaction where released sensitizer in the extracellular matrix provides positive feedback to assist in the release of additional sensitizer. The photokilling of the glioma cells was analyzed by global toxicity and live/dead assays, where a killing radius around the tip with ~0.3 mm precision was achieved. The implication of these results for a new PDT tool of hard-to-resect tumors, e.g. in the brain, is discussed.

  • RESEARCH ARTICLE: Retarded Photooxidation of Cyamemazine in Biomimetic Microenvironments

    RESEARCH ARTICLE: Retarded Photooxidation of Cyamemazine in Biomimetic Microenvironments

    Cyamemazine (CMZ) is a neuroleptic drug that mediates cutaneous phototoxicity in humans. Here, the photobehavior of CMZ has been examined within α1-acid glycoproteins, β- and γ-cyclodextrins and SDS micelles. In all these microenvironments, CMZ emission was enhanced and blue-shifted, and its lifetime was longer. Irradiation of the entrapped drug at 355 nm, under air; led to the N,S-dioxide. Within glycoproteins or SDS micelles the reaction was clearly slower than in phosphate buffered solution (PBS); protection by cyclodextrins was less marked. Transient absorption spectroscopy in PBS revealed formation of the triplet state (3CMZ*) and the radical cation (CMZ+•). Upon addition of glycoprotein, the contribution of CMZ+• became negligible, whereas 3CMZ* dominated the spectra; in addition, the triplet lifetime became considerably longer. In cyclodextrins, this occurred to a lower extent. In all microheterogeneous systems, quenching by oxygen was slower than in solution; this was most remarkable inside glycoproteins. The highest protection from photooxidation was achieved inside SDS micelles. The results are consistent with photooxidation of CMZ through photoionization and subsequent trapping of the resulting radical cation by oxygen. This reaction is extremely sensitive to the medium and constitutes an appropriate probe for localization of the drug within a variety of biological compartments.

  • INVITED REVIEW: Chemical and Biological Mechanisms of Pathogen Reduction Technologies

    INVITED REVIEW: Chemical and Biological Mechanisms of Pathogen Reduction Technologies

    Within the last decade new technologies have been developed and implemented which employ light, often in the presence of a photosensitizer, to inactivate pathogens that reside in human blood products for the purpose of transfusion. These pathogen reduction technologies attempt to find the proper balance between pathogen kill and cell quality. Each system utilizes various chemistries that not only impact which pathogens they can inactivate and how, but also how the treatments affect the plasma and cellular proteins and to what degree. This paper aims to present the various chemical mechanisms for pathogen reduction in transfusion medicine that are currently practiced or in development.

  • RESEARCH ARTICLE: The Number of Accumulated Photons and the Quality of Stimulated Emission Depletion Lifetime Images

    RESEARCH ARTICLE: The Number of Accumulated Photons and the Quality of Stimulated Emission Depletion Lifetime Images

    Time binning is used to increase the number of photon counts in the peak channel of stimulated emission depletion fluorescence lifetime decay curves to determine how it affects the resulting lifetime image. The fluorescence lifetime of the fluorophore, Alexa Fluor 594 phalloidin, bound to F-actin is probed in cultured S2 cells at a spatial resolution of ~40 nm. This corresponds to a 10-fold smaller probe volume compared to confocal imaging, and a reduced number of photons contributing to the signal. Pixel-by-pixel fluorescence lifetime measurements and error analysis show that an average of 40 ± 30 photon counts in the peak channel with a signal-to-noise ratio of 20 is enough to calculate a reliable fluorescence lifetime from a single exponential fluorescence decay. No heterogeneity in the actin cytoskeleton in different regions of the cultured cells was measured in the 40–400 nm spatial regime.

  • RESEARCH NOTE: Preparation and Characterization of Uniform Near IR Polystyrene Nanoparticles

    RESEARCH NOTE: Preparation and Characterization of Uniform Near IR Polystyrene Nanoparticles

    Biomaterials for in vivo fluorescence imaging are required to be biocompatible, nontoxic, photostable and highly fluorescent. Fluorescence must be in the near infrared (NIR) region of the electromagnetic spectrum to avoid absorption and autofluorescence of endogenous tissues. NIR fluorescent polystyrene nanoparticles may be considered ideal biomaterials for in vivo imaging applications. These NIR nanoparticles were prepared by a swelling process of polystyrene template nanoparticles with a hydrophobic NIR dye dissolved in a water-miscible swelling solvent, a method developed for preparation of nonbiodegradable nanoparticles, for NIR fluorescent bioimaging applications. This method overcomes common problems that occur with dye entrapment during nanoparticle formation such as loss of fluorescence and size polydispersity. Fluorescence intensity of the nanoparticles was found to be size dependent, and was optimized for differently sized nanoparticles. The resulting NIR nanoparticles were also found to be more fluorescent and highly photostable compared to the free dye in solution, showing their potential as biomaterials for in vivo fluorescence imaging.

  • RESEARCH ARTICLE: Analysis of Photoexcitation Energy Dependence in the Photoluminescence of Firefly Luciferin

    RESEARCH ARTICLE: Analysis of Photoexcitation Energy Dependence in the Photoluminescence of Firefly Luciferin

    S1 and S0 relative free energies of luciferin and its conjugate acids and bases. Black circles: Phenol–LH−; red circles: L2−; green circles: LH2; blue circles: Phenolate–LH−; red squares: L2−–3H+; filled red circles: L2−–3′H+; black squares: Phenol–LH−–3H+; filled black circles: Phenol–LH−–3′H+; green squares: LH2–3H+; filled green circles: LH2–3′H+; blue square: Phenolate–LH−–3H+; filled blue circles: Phenolate–LH−–3′H+.

  • RESEARCH ARTICLE: “Pointsource” Delivery of a Photosensitizer Drug and Singlet Oxygen: Eradication of Glioma Cells In Vitro
  • RESEARCH ARTICLE: Retarded Photooxidation of Cyamemazine in Biomimetic Microenvironments
  • INVITED REVIEW: Chemical and Biological Mechanisms of Pathogen Reduction Technologies
  • RESEARCH ARTICLE: The Number of Accumulated Photons and the Quality of Stimulated Emission Depletion Lifetime Images
  • RESEARCH NOTE: Preparation and Characterization of Uniform Near IR Polystyrene Nanoparticles
  • RESEARCH ARTICLE: Analysis of Photoexcitation Energy Dependence in the Photoluminescence of Firefly Luciferin

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16th International Congress on Photobiology

September 8th – 12th, 2014

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Ultraviolet light combined with or without a photosensitizer (e.g. riboflavin, amotosalen, and methylene blue) interacts with nucleic acids to prevent replication, thus reducing the pathogen load in treated blood products intended for transfusion and ultimately improving blood safety. The mechanisms are discussed in the review paper “Chemical and Biological Mechanisms of Pathogen Reduction Technologies” by Janna Mundt and coworkers on pages 957 – 964 in this issue.
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