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Molecules 2016, 21(4), 439;

Photophysical Characterization and in Vitro Phototoxicity Evaluation of 5,10,15,20-Tetra(quinolin-2-yl)porphyrin as a Potential Sensitizer for Photodynamic Therapy

Molecular Physical Chemistry I & D Unit and Department of Life Sciences, University of Coimbra, Coimbra 3000-456, Portugal
Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
Research Centre for Environment, Genetics and Oncobiology (CIMAGO), University of Coimbra, Coimbra 3004-504, Portugal
Authors to whom correspondence should be addressed.
Academic Editors: Derek J. McPhee, M. Graça P. M. S. Neves and M. Amparo F. Faustino
Received: 12 January 2016 / Revised: 14 March 2016 / Accepted: 24 March 2016 / Published: 31 March 2016
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Photodynamic therapy (PDT) is a selective and minimally invasive therapeutic approach, involving the combination of a light-sensitive compound, called a photosensitizer (PS), visible light and molecular oxygen. The interaction of these per se harmless agents results in the production of reactive species. This triggers a series of cellular events that culminate in the selective destruction of cancer cells, inside which the photosensitizer preferentially accumulates. The search for ideal PDT photosensitizers has been a very active field of research, with a special focus on porphyrins and porphyrin-related macrocycle molecules. The present study describes the photophysical characterization and in vitro phototoxicity evaluation of 5,10,15,20-tetra(quinolin-2-yl)porphyrin (2-TQP) as a potential PDT photosensitizer. Molar absorption coefficients were determined from the corresponding absorption spectrum, the fluorescence quantum yield was calculated using 5,10,15,20-tetraphenylporphyrin (TPP) as a standard and the quantum yield of singlet oxygen generation was determined by direct phosphorescence measurements. Toxicity evaluations (in the presence and absence of irradiation) were performed against HT29 colorectal adenocarcinoma cancer cells. The results from this preliminary study show that the hydrophobic 2-TQP fulfills several critical requirements for a good PDT photosensitizer, namely a high quantum yield of singlet oxygen generation (Φ 0.62), absence of dark toxicity and significant in vitro phototoxicity for concentrations in the micromolar range. View Full-Text
Keywords: photodynamic therapy; photosensitizers; porphyrins; cancer; HT29 cells photodynamic therapy; photosensitizers; porphyrins; cancer; HT29 cells

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Costa, L.D.; Silva, J.A.; Fonseca, S.M.; Arranja, C.T.; Urbano, A.M.; Sobral, A.J. Photophysical Characterization and in Vitro Phototoxicity Evaluation of 5,10,15,20-Tetra(quinolin-2-yl)porphyrin as a Potential Sensitizer for Photodynamic Therapy. Molecules 2016, 21, 439.

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