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

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          Abstract

          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.

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          Most cited references 37

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          The physics, biophysics and technology of photodynamic therapy.

          Photodynamic therapy (PDT) uses light-activated drugs to treat diseases ranging from cancer to age-related macular degeneration and antibiotic-resistant infections. This paper reviews the current status of PDT with an emphasis on the contributions of physics, biophysics and technology, and the challenges remaining in the optimization and adoption of this treatment modality. A theme of the review is the complexity of PDT dosimetry due to the dynamic nature of the three essential components -- light, photosensitizer and oxygen. Considerable progress has been made in understanding the problem and in developing instruments to measure all three, so that optimization of individual PDT treatments is becoming a feasible target. The final section of the review introduces some new frontiers of research including low dose rate (metronomic) PDT, two-photon PDT, activatable PDT molecular beacons and nanoparticle-based PDT.
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            Definition of type I and type II photosensitized oxidation.

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              Rate Constants for the Decay and Reactions of the Lowest Electronically Excited Singlet State of Molecular Oxygen in Solution. An Expanded and Revised Compilation

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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                Cancers (Basel)
                Cancers (Basel)
                cancers
                Cancers
                MDPI
                2072-6694
                06 December 2016
                December 2016
                : 8
                : 12
                Affiliations
                [1 ]Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA; mickim@ 123456sas.upenn.edu (M.M.K.); Rozhin.Penjweini@ 123456uphs.upenn.edu (R.P.)
                [2 ]Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
                [3 ]Department of Electronic and Nanoscale Engineering, University of Glasgow, Glasgow G12 8LT, UK; Nathan.Gemmell@ 123456glasgow.ac.uk (N.R.G.); Robert.Hadfield@ 123456glasgow.ac.uk (R.H.H.)
                [4 ]Princess Margaret Cancer Centre, University of Toronto, ON M5G 1L7, Canada; israel.veilleux@ 123456uhnresearch.ca (I.V.); wilson@ 123456uhnresearch.ca (B.C.W.)
                [5 ]Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK; A.McCarthy@ 123456hw.ac.uk (A.M.); g.s.buller@ 123456hw.ac.uk (G.S.B.)
                Author notes
                [* ]Correspondence: tzhu@ 123456mail.med.upenn.edu ; Tel.: +1-215-662-4043
                Article
                cancers-08-00109
                10.3390/cancers8120109
                5187507
                27929427
                © 2016 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license ( http://creativecommons.org/licenses/by/4.0/).

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