American Society for Photobiology

ASP Conference 2016: 21-26 May 2016
Tampa Marriott Waterside Hotel & Marina


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27 - Current Topics in Photobiology, II

Florida 3   08:00 - 09:45

Chair(s): Carlos Crespo , Marvin Pollum
 
27-1   08:00  Singlet Oxygen at the Nanoscale. N Macia, University of Calgary ; O Planas, University Ramon Llull; S Nonell, University Ramon Llull; B Heyne*, University of Calgary

Abstract: Singlet oxygen remains at the forefront of research, whether it is in bacterial photo-inactivation, in cancer treatment, or in nanoscience. Contrary to other reactive oxygen species, singlet oxygen is emissive, and by consequent its demeanor could be monitored in vivo. Due to its convenient mode of generation by photosensitization, singlet oxygen is the holly grail of imaging techniques, as it can offer both temporal and spatial resolution. However, there is a catch. Only one singlet oxygen molecule in 0.1 million is emissive! Therefore, monitoring this species in vivo poses a great challenge. Challenge, which can only be overcome by developing novel monitoring tools that largely outperform the current ones. In this study, we have engineered a series of novel core-shell nanoparticle where the plasmonic core of the nanoparticles plays a dual role of enhancing both the production of singlet oxygen and its radiative decay. By consequence, our plasmonic hybrid nanoparticles generate a signal of singlet oxygen phosphorescence significantly more intense than expected from the amount of singlet oxygen generated in solution. We have taken advantage of this dual amplification to detect singlet oxygen emission signal in biological media, such as Gram-negative and Gram-positive bacteria. We demonstrate the plasmonic hybrid nanoparticles are endowed with strong light-induced antimicrobial activity even towards the more resilient Gram-negative bacteria.

27-2   08:15  Cellular Killing and Transformation by Ultraviolet and Ionizing Radiation: a Fundamental Difference JC Sutherland*, Augusta University

Abstract: The clonogenic survival curves of cells growing in vitro as a function of dose are generally similar for ultraviolet (UV) and ionizing radiations, and are often represented by similar mathematical expressions. But the validity of some widely used expressions for survival curves are problematic because the underlying theory ignores repair. Cellular transformation is frequently described by a linear-quadratic (LQ) function, because they are often non-linear. However, this description is essentially ad hoc as it is not based on underlying assumptions about the transformation process. In addition, this fails to account for the plateau in the plot of transformants per survivor at doses yielding very low (< 10^-3) survival. The repair-dependent theory of cell survival and transformation uses a single set of assumptions to characterize both survival and transformation, and can describe the shapes of both, including the high-dose plateau in survival frequency.* But there is a fundamental difference between the results for mammalian cells exposed to UV and ionizing radiations. In the case of x-rays and neutrons, the survival curves can be fit by the expressions generated by the repair-dependent model only if different parameters are used for the two processes. In contrast, in the case of UV, the dose-response curves for survival and transformation can be fit using the same values of the shared parameters. This difference is due to the fact that the theory underlying the repair-dependent model is based on the assumption that a single radiation event never results in more than one potentially lethal damage. This is true for the absorption of a UV photon, but generally not true for a radiation process, such as the absorption of an x-ray that may result in an energetic electron, or the impact of a neutron, that can result in an energetic proton. Both processes can produce multiple damages per event. * Sutherland, J. (2014). Physics in Medicine and Biology 59: 5073"5090.

27-3   08:30  The CIE action spectrum for pre-vitamin D requires adjustment to be valid in vivo for 25(OH)D in humans PA Philipsen*, Bispebjerg Hospital, Denmark ; KA Morgan, King's College London, United Kingdom; G Harrison, King's College London, United Kingdom; B Petersen, Bispebjerg Hospital, Denmark; HC Wulf, Bispebjerg Hospital, Denmark; AR Young, King's College London, United Kingdom

Abstract: The validity of the CIE action spectrum for the conversion of 7-dehyrocholesterol (7-DHC) to pre-vitamin D3 has been questioned (Norval et al., PPS, 2010). We designed experiments to test this spectrum and compare it with 2 others (Olds, PhD thesis, 2009 and Bolsee et al. Appl. Optics, 2010) that are blue-shifted compared with the CIE spectrum. This was done with full body (FB - 86%) or partial body (PB - ~5%) exposures, each with 3 very different UVR emission spectra (FB: Arimed B, UV6, Waldmann F85/PUVA; PB: UV6, two solar simulated spectra with different amounts of UVB (2% and 8%)). Each participant had 5 serial exposures of 2 SED with intervals of 2-3 days. Blood was drawn before each exposure and 2 days after the last exposure and analyzed for 25(OH)D by LCMS. 75 participants (skin type I/II, 29M/46F, mean age 26.3±4.9y) completed the study, done in winter-spring 2011-2014 to minimize ambient UVR influence. Individual increases in 25(OH)D vs SED were linear with accumulated dose and dependent on baseline 25(OH)D value. The slopes of the curves were significantly different (p <0.0001) for FB and PB. We weighed the UVR dose (J/m^2) response curves with the three action spectra. Our hypothesis was that the correct action spectrum would result in dose response slopes that were independent of emission spectra. The CIE spectrum resulted in significant differences in dose response slopes for PB: p<0.0001 and FB: p<0.00001. This was also the case for the Olds spectrum, PB: p=0.004 and FB: p<0.00001. However, weighting with the Bolsee spectrum showed non-significant differences for PB: p=0.841 (r^2=0.83) and just significant differences for FB: p=0.049 (r^2=0.84). We also tested the effect of a 1-9nm blue-shift on the CIE spectrum in 1 nm steps. For the PB there is no significant difference in slope between UVR sources for 3 - 6 nm shifts (p > 0.12) and for the FB there is no significant differences for 4 " 6 nm shifts (p > 0.18). A 5 nm blue-shift gave the best fits for both PB (r^2=0.83) and FB (r^2=0.85) studies, where the slopes for the different UVR sources were equal. We conclude that the CIE action spectrum needs a 5nm blue-shift, which is a better match with the 292 nm 7-DHC absorption peak. This supports a suggested blue-shift (McKenzie et al., PPS, 2012:11:1174). Furthermore, our data suggest that UVA has no significant effect on vitamin D production.

27-4   08:45  Quantitative Imaging of Oxygen in Tissues with Bright Porphyrin Phosphors and Bandages CL Evans*, Wellman Center for Photomedicine, Harvard Medical School, Massachusetts General Hospital

Abstract: Proper tissue oxygenation is crucial in situations ranging from treating chronic wounds to therapeutic intervention in cancer. Our research has been focused on developing a platform for real-time, quantative imaging of oxygen tension within tissue. First, we have developed a set of click-chemistry compatible, bright planar porphyrin molecular oxygen sensors based on near-infrared phosphorescence quenching. These meso-unsubstituted molecules have considerably higher phosphorescence quantum yield than existing commercial probes, enabling rapid oxygen tension sensing and image acquisition. Second, we have developed a simple, but extensible, click-chemistry based scheme that allows for the rapid growth of custom dendrimer layers surrounding these new porphyrin sensors that not only provide an extended oxygen sensing dynamic range, but are also designed to enable cellular uptake even in highly acidic tumor compartments. These new sensors have been tested in a three-dimensional in vitro model of ovarian cancer where they readily penetrate throughout large nodules and report oxygenation changes. Third, to translate these oxygen sensors into the clinic, we have developed oxygen sensing bandages that can be applied to skin or wounds for trancutaneous oxygen imaging. The formulation of the bandage enables the simple readout of tissue oxygenation with commicial cameras and smartphones for rapid quantification of oxygen by untrained operators.

27-5   09:00  Photodynamic therapy-based combinations overcome tumor endothelial cell-induced heterogeneity and chemoresistance in 3D ovarian cancer cultures I Rizvi*, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School ; E Briars, Wellman Center for Photomedicine, Massachusetts General Hospital; A-L Bulin, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School; S Anbil, Wellman Center for Photomedicine, Massachusetts General Hospital and Howard Hughes Medical Institute; D Vecchio, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School; M Broekgaarden, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School; W Hanna, University of Massachusetts Boston; JP Celli, University of Massachusetts Boston; T Hasan, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School

Abstract: Identifying the molecular, cellular, and microenvironmental cues that lead to heterogeneity and treatment resistance is critical to developing strategies to target unresponsive regions of stubborn disease. Photodynamic therapy (PDT) has been shown to synergize with conventional agents and to overcome the evasion pathways that cause resistance. Developing PDT-based combinations that target resistant tumor populations and cooperate mechanistically with conventional agents is an increasingly promising approach to improve therapeutic efficacy while minimizing toxicity, particularly in complex disease sites. Here, 3D in vitro models that restore the architectural features, physical stress and heterocellular signaling experienced by tumors in vivo are described in the context of metastatic ovarian cancer, the leading cause of death among gynecologic malignancies. The potential value, and challenges, associated with developing complex cell-based models that include communication with stromal partners (e.g. tumor endothelial cells, which are emerging as dynamic regulators of cell cycle and treatment resistance), will be presented, with a particular focus on addressing resistance to conventional agents with PDT-based combination regimens. We show that priming hetero-cellular ovarian cancer nodules with verteporfin-based PDT prior to treatment with chemotherapy (carboplatin and paclitaxel) significantly decreases the size and viability of complex 3D tumors and decreases heterogeneity in response. The potential molecular and phenotypic basis of this enhanced efficacy and predictability in response will be presented.

27-6   09:15  Wavelength Dependent Increase In Cell Sensitivity After Glutathione Inhibition By Methacrylate Monomers T Christensen*, Norwegian Radiation Protection Authority and Centre for Environmental Radioactivity (CERAD CoE) ; T Danielsen, Norwegian Radiation Protection Authority, Norwegian Institute of Public Health and Centre for Environmental Radioactivity (CERAD CoE); A Jaworska, Norwegian Radiation Protection Authority and Centre for Environmental Radioactivity (CERAD CoE); G Brunborg, Norwegian Institute of Public Health; EM Bruzell, Nordic Institute of Dental Materials

Abstract: Reduction in the amount of glutathione (GSH) in cells can lead to increased sensitivity to physical and chemical agents. Methacrylate monomers (MM) are precursors of polymethacrylates which are used in dental and medical biomaterials and in a wide variety of other products. MM can increase cell sensitivity to long wavelength ultraviolet and visible radiation. The aim of this study is to elucidate if MM can induce sensitivity also to shorter wavelength radiation. A concentration of 3 mM 2-hydroxyethyl methacrylate (HEMA) in a serum free medium was added to ZF4 zebrafish embryo fibroblasts during logarithmic growth and kept on the cells for up to 4 h. Cell death was assayed by the Alamar blue assay 3 days after irradiation. The level of GSH was quantified by a commercial glutathione assay kit. Buthionine sulphoximine (BSO) was used as positive control for depletion of GSH. HEMA reduced the level of GSH relative to control. The cells were irradiated with either broadband UVA (Osram 9W/78), UVB (Philips 9 W PL 12) or 225 keV X-rays. HEMA was non-toxic to the cells under these conditions and did not absorb optical radiation with wavelength longer than 250 nm. Following cell pretreatment with HEMA, the survival relative to controls was reduced from 72.3 % to 23.0 % after exposure to 100 kJ/m^2 of UVA, from 75.3 % to 65.5 % after exposure to 0.25 kJ/m^2 UVB and from 70.0 % to 67.9 % after 16 Gy X-rays. The change in cellular sensitivity due to HEMA was more pronounced with UVA- than with UVB- and X-ray irradiation. UVA-induced cellular damage is characterized by formation of reactive oxygen species, most notably hydrogen peroxide. UVB damage, on the other hand, includes direct interaction with DNA, whereas ionizing radiation induces breaks in the DNA strands, by direct hits or via the formation of hydroxyl radicals. These different mechanisms of action are likely to be associated with the observed sensitivity modifications due to HEMA treatment.



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