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Shields L.,St Lukes Hospital | Shields L.,University College Dublin | Vega-Carrascal I.,Focas Institute | Lyng F.M.,Focas Institute | And 3 more authors.
Radiation Research | Year: 2014

Interest in out-of-field radiation dose has been increasing with the introduction of new techniques, such as volumetric modulated arc therapy (VMAT). These new techniques offer superior conformity of high-dose regions to the target compared to conventional techniques, however more normal tissue is exposed to low-dose radiation with VMAT. There is a potential increase in radiobiological effectiveness associated with lower energy photons delivered during VMAT as normal cells are exposed to a temporal change in incident photon energy spectrum. During VMAT deliveries, normal cells can be exposed to the primary radiation beam, as well as to transmission and scatter radiation. The impact of low-dose radiation, radiation-induced bystander effect and change in energy spectrum on normal cells is not well understood. The current study examined cell survival and DNA damage in normal prostate cells after exposure to out-of-field radiation both with and without the transfer of bystander factors. The effect of a change in energy spectrum out-of-field compared to in-field was also investigated. Prostate cancer (LNCaP) and normal prostate (PNT1A) cells were placed in-field and out-of-field, respectively, with the PNT1A cells being located 1 cm from the field edge when in-field cells were being irradiated with 2 Gy. Clonogenic and γ-H2AX assays were performed postirradiation to examine cell survival and DNA damage. The assays were repeated when bystander factors from the LNCaP cells were transferred to the PNT1A cells and also when the PNT1A cells were irradiated in-field to a different energy spectrum. An average out-of-field dose of 10.8 ± 4.2 cGy produced a significant reduction in colony volume and increase in the number of γ-H2AX foci/cell in the PNT1A cells compared to the sham-irradiated control cells. An adaptive response was observed in the PNT1A cells having first received a low out-of-field dose and then the bystander factors. The PNT1A cells showed a significant increase in γ-H2AX foci formation when irradiated to 20 cGy in-field in comparison to out-of-field. However, no significant difference in cell survival or colony volume was observed whether the PNT1A cells were irradiated in-field or out-of-field. Out-of-field radiation dose alone can have a damaging effect on the proliferation of PNT1A cells when a clinically relevant dose of 2 Gy is delivered in in-field. Out-of-field radiation with the transfer of bystander factors induces an adaptive response in the PNT1A cells. © 2014 by Radiation Research Society.

Etacheri V.,FOCAS Institute | Etacheri V.,Dublin Institute of Technology | Seery M.K.,Dublin Institute of Technology | Hinder S.J.,University of Surrey | Pillai S.C.,FOCAS Institute
Inorganic Chemistry | Year: 2012

Highly visible-light-active S,N-codoped anatase-rutile heterojunctions are reported for the first time. The formation of heterojunctions at a relatively low temperature and visible-light activity are achieved through thiourea modification of the peroxo-titania complex. FT-IR spectroscopic studies indicated the formation of a Ti4+-thiourea complex upon reaction between peroxo-titania complex and thiourea. Decomposition of the Ti 4+-thiourea complex and formation of visible-light-active S,N-codoped TiO2 heterojunctions are confirmed using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV/vis spectroscopic studies. Existence of sulfur as sulfate ions (S6+) and nitrogen as lattice (N-Ti-N) and interstitial (Ti-N-O) species in heterojunctions are identified using X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopic techniques. UV-vis and valence band XPS studies of these S,N-codoped heterojunctions proved the fact that the formation of isolated S 3p, N 2p, and η * N-O states between the valence and conduction bands are responsible for the visible-light absorption. Titanium dioxide obtained from the peroxo-titania complex exists as pure anatase up to a calcination temperature as high as 900 °C. Whereas, thiourea-modified samples are converted to S,N-codoped anatase-rutile heterojunctions at a temperature as low as 500 °C. The most active S,N-codoped heterojunction 0.2 TU-TiO2 calcined at 600 °C exhibits a 2-fold and 8-fold increase in visible-light photocatalytic activities in contrast to the control sample and the commercial photocatalyst Degussa P-25, respectively. It is proposed that the efficient electron-hole separation due to anatase to rutile electron transfer is responsible for the superior visible-light-induced photocatalytic activities of S,N-codoped heterojunctions. © 2012 American Chemical Society.

Di Lorenzo M.L.,CNR Institute of Chemistry and Technology of Polymers | Cocca M.,CNR Institute of Chemistry and Technology of Polymers | Gentile G.,CNR Institute of Chemistry and Technology of Polymers | Avella M.,CNR Institute of Chemistry and Technology of Polymers | And 5 more authors.
Journal of Colloid and Interface Science | Year: 2013

This manuscript details the preparation and characterization of luminescent organogels in toluene. Gels were prepared by using 12-hydroxystearic acid (12HSA) as gelator and different amounts of thenoyltrifluoroacetonato 1,10-phenanthroline europium(III) complex (Eu(TTA)3phen). The gelation properties and the thermoreversible behavior from solid-like to liquid systems were investigated by differential scanning calorimetry. At higher concentration, an interaction of Eu complex with the polar group of the gelator was revealed by DSC and FTIR analyses. The spectroscopic behavior of the complex was investigated in toluene solution and in the gel state. TEM analysis revealed that 12HSA is able to solvate the Eu diketonate complex inducing a remarkable increase in the Eu-Eu distance. The Eu(TTA)3phen in the gel state exhibits a very high emission quantum yield, Φ, which was found to be independent of Eu complex concentration, at least for the composition range analyzed. These results indicate that 12HSA organogels containing Eu(TTA)3phen are promising materials for optical applications. © 2013 Elsevier Inc.

PubMed | Focas Institute, Institute of Technology Tallaght and Bulgarian Academy of Science
Type: | Journal: Journal of inorganic biochemistry | Year: 2015

Silver(I) complexes of coumarin-based ligands and one of their phenanthroline (phen) adducts have been prepared and characterized using microanalytical data, molar conductivity, IR, (1)H and (13)C NMR, UV-Vis, and atomic absorption (AAS) spectroscopies. The binding modes of the coumarin-based ligands and the most probable structure of their Ag(I) complexes were predicted by means of molecular modeling and calculations of their IR, NMR, and absorption spectra using density functional theory (DFT). The cytotoxicity of the compounds studied against human-derived hepatic carcinoma cells (Hep-G2) and a renal cancer cell line (A498) showed that the complexes were more cytotoxic than the clinically used chemotherapeutic, mitoxantrone. The compounds showed little interaction with DNA and also did not show nuclease activity but manifested excellent superoxide dismutase activity which may indicate that their mechanism of action is quite different to many metal-based therapeutics.

Creaven B.S.,Institute of Technology Tallaght | Czegledi E.,University of Szeged | Devereux M.,Focas Institute | Enyedy E.A.,University of Szeged | And 9 more authors.
Dalton Transactions | Year: 2010

The coordination modes of copper(ii) complexes of Schiff base-derived coumarin ligands, which had previously shown good anti-Candida activity, were investigated by pH-potentiometric and UV-Vis spectroscopic methods. These studies confirmed the coordination mode of the ligands to be through the N of the imine and deprotonated phenol of the coumarin-derived ligand in solution. In addition, the more active complexes and their corresponding ligands were investigated in the presence of copper(ii) in liquid and frozen solution by ESR spectroscopic methods. A series of secondary amine derivatives of the Schiff base ligands, were isolated with good solubility characteristics but showed little anti-Candida activity. However, cytotoxicity studies of the secondary amines, together with the copper complexes and their corresponding ligands, against human colon cancer and human breast cancer cells identified the chemotherapeutic potential of these new ligands. © The Royal Society of Chemistry 2010.

Zanchetta L.M.,Institute of Technology Sligo | Garcia A.,Focas Institute | Lyng F.,Focas Institute | Walsh J.,Dublin Institute of Technology | Murphy J.E.J.,Institute of Technology Sligo
International Journal of Radiation Biology | Year: 2011

Purpose: To assess changes in mitochondrial morphology and mitophagy induced by simulated sunlight irradiation (SSI) and how these changes are modulated by mitochondrial activity and energy source. Materials and methods: Human malignant amelanotic melanoma A375 cells were pre-treated with either a mitochondrial activity enhancer, uncoupler or were either melanin or glutamine supplemented/starved for 4 hours pre-exposure to sunlight. A Q-Sun Solar Simulator (Q-Lab, Homestead, FL, USA) was employed to expose cells to simulated sunlight. Confocal microscopy imaging of A375 cells co-loaded with mitochondria and lysosome-specific fluorescent dyes was used to identify these organelles and predict mitophagic events. Results: SSI induces pronounced changes in mitochondrial dynamics and mitophagy in exposed skin cells compared to control and these effects were modified by both glutamine and melanin. Conclusions: Mitochondrial dynamics and rate of mitophagy in melanoma cells are sensitive to even short bursts of environmentally relevant SSI. Mitochondrial dynamics, and its modulation, may also play a role in mitophagy regulation, cell survival and proliferation post SSI. © 2011 Informa UK, Ltd.

Murray J.,Institute of Technology Sligo | Gannon S.,Focas Institute | Rawe S.,Dublin Institute of Technology | Murphy J.E.J.,Institute of Technology Sligo
Anticancer Research | Year: 2014

Background/Aim: Hypoxia can affect chemo-therapeutic drug efficacy in cancer patients, yet related in vitro assays in oxygen-rich environment remain the norm. Such levels are well beyond normoxic/hypoxic levels typically experienced by normal tissues/tumor masses. The present study evaluated how artesunate anti-tumor efficacy is modulated by oxygen availability in HeLa cells and its implications for future in vitro analyses. Materials and Methods: Real-time cell analysis was employed to evaluate HeLa cell toxicity to artesunate at 21%, 4% or 1% oxygen. Cell count analysis was performed to validate real-time data. Results: An increase in artesunate efficacy was observed when oxygen concentration was reduced from atmospheric levels down to in vivo-relevant levels. Conclusion: Artesunate is more potent than originally reported using standard oxygen conditions during in vitro studies. The inclusion of this long overlooked variable as standard in future in vitro analysis procedures is warranted.

Zanchetta L.M.,Institute of Technology Sligo | Zanchetta L.M.,Focas Institute | Kirk D.,Focas Institute | Lyng F.,Focas Institute | And 2 more authors.
Photodermatology Photoimmunology and Photomedicine | Year: 2010

Background: Solar ultraviolet radiation (UVR) is the principal etiological factor in skin carcinogenesis. In vivo and in vitro studies have demonstrated previously that oxidative DNA damage, mitochondrial mass and mitochondrial membrane potential (MMP) changes are associated with skin cell response to UVR stress.Methods: Spontaneously immortalized human skin keratinocytes were irradiated with increasing sub-lethal doses of simulated sunlight irradiation (SSI) using a Q-Sun solar simulator. The effects of SSI on reactive oxygen species (ROS) formation, mitochondrial mass and MMP were then determined.Results: SSI induced mitochondrial mass increase post low SSI (0.25-2.5 J/cm2), whereas higher SSI doses (5.0 and 7.5 J/cm2) decreased mitochondrial mass. Mitochondrial mass increased with time post 5.0 J/cm2 irradiation and all changes in mass were independent of cell density status. Changes in ROS and MMP were cell density dependent. Additionally, an inverted dose-dependent decrease in ROS formation was observed 3 h post SSI with the lower SSI dose (0.25 J/cm2).Conclusions: Observations from the present study suggest that changes in the cell's microenvironment (modeled through varying cell density) influence changes in MMP and ROS detoxifying responses in sun-exposed skin cells. © 2010 John Wiley & Sons A/S.

Chandra S.,Focas Institute | Doran J.,Focas Institute | McCormack S.J.,Trinity College Dublin | Kennedy M.,Focas Institute | Chatten A.J.,Imperial College London
Solar Energy Materials and Solar Cells | Year: 2012

Plasmonic excitation enhanced fluorescence of CdSe/ZnS core-shell quantum dots (QDs) in the presence of Au nanoparticles (NPs) has been studied for application in quantum dot solar concentrator (QDSC) devices. We observe that there is an optimal concentration of Au NPs that gives a maximum 53% fluorescence emission enhancement for the particular QD/Au NP composite studied. The optimal concentration depends on the coupling and spacing between neighboring QDs and Au NPs. We show the continuous transition from fluorescence enhancement to quenching, depending on Au NP concentration. The locally enhanced electromagnetic field induced by the surface plasmon resonance in the Au NPs leads to an increased excitation rate for the QDs. This is evidenced by excitation wavelength dependent fluorescence enhancement, where the locally enhanced field around the Au NPs is more pronounced close to the surface plasmon resonance (SPR) wavelength. However, at higher concentrations of Au NPs non-radiative energy transfer from the QDs to the Au NPs particles leads to a decrease of the emission, which is confirmed by detection of both a double exponential lifetime decay in, and a decrease in the lifetime of the QDs. The overall fluorescence emission enhancement depends on these competing effects; increased excitation rate and non-radiative energy transfer. © 2011 Elsevier B.V. All rights reserved.

Lemarchand P.,Focas Institute | Doran J.,Focas Institute | Norton B.,Focas Institute
Energy Procedia | Year: 2014

One presents in this paper an idea to use switchable technologies to independently control the solar heat flow and the visible light transmission through windows, and potentially collect infrared radiant power on a photovoltaic cell. The system uses chiral liquid crystal and suspended particle device switchable technologies that are electronically tuned to optically control the quantity of infrared light rejected, the visible light transmission and the optical path to internally reflect the light and collect it on the photovoltaic cell. A characterized suspended particle device showed an average 48.5% to 1.3% transmission respectively in the transparent and opaque states of the window. A second characterization of a chiral liquid crystal mirror manufactured to reflect the visible range showed an average transmission modulation between 84% and 3% over 250nm reflection range respectively in the transparent and reflective states at small light incidence angles. Transmission is however significantly increasing in the reflective state while increasing light incidence angle and considered in ray-tracing simulation of the system. A ray tracing software has been developed to simulate the performance of a window 50cm height by 50cm long and 5.5cm wide consisting of two chiral liquid crystal mirrors and using the characterization results. Adaptation of the mirrors configuration was considered to collect light on the cell at various zenith and azimuth solar angles. Simulation results showed no significant benefit of internally reflecting the light to concentrate it on the photovoltaic cell located in the windows frame. However, an infrared chiral mirror with a reflection bandwidth wider than the wavelength range to modulate in transmission could potentially control solar heat radiation through the window between ~ 80% and 5% independently of the light incidence angle. The window system would technically benefit of a combined suspended particle device solely absorbing the visible range to realize the desired hybrid system. © 2014 The Authors. Published by Elsevier Ltd.

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