title: Photophysical Characterization and in Vitro Phototoxicity Evaluation of 5,10,15,20-Tetra(quinolin-2-yl)porphyrin as a Potential Sensitizer for Photodynamic Therapy.
abstract: 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.
authors.affiliation: Molecular Physical Chemistry I & D Unit and Department of Life Sciences, University of Coimbra, Coimbra 3000-456, Portugal. leticiadanielacosta@gmail.com.
authors.forename: Letícia D
authors.initials: LD
authors.lastname: Costa
authors.affiliation: Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal. joana.a.silva@uc.pt.
authors.forename: Joana de A
authors.initials: Jde A
authors.lastname: e Silva
authors.affiliation: Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal. sfonseca@qui.uc.pt.
authors.forename: Sofia M
authors.initials: SM
authors.lastname: Fonseca
authors.affiliation: Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal. claudia.arranja@gmail.com.
authors.forename: Cláudia T
authors.initials: CT
authors.lastname: Arranja
authors.affiliation: Molecular Physical Chemistry I & D Unit and Department of Life Sciences, University of Coimbra, Coimbra 3000-456, Portugal. amurbano@ci.uc.pt.|Research Centre for Environment, Genetics and Oncobiology (CIMAGO), University of Coimbra, Coimbra 3004-504, Portugal. amurbano@ci.uc.pt.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Urbano
authors.affiliation: Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal. asobral@ci.uc.pt.
authors.forename: Abilio J F N
authors.initials: AJ
authors.lastname: Sobral
mesh_terms: D000818:Animals; D015179:Colorectal Neoplasms / Q000628:therapy*; D019073:HT29 Cells; D006801:Humans; D008027:Light; D015394:Molecular Structure; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000737:chemistry*; D011166:Porphyrins / Q000008:administration & dosage / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: C509964:5,10,15,20-tetraphenylporphyrin; D017319:Photosensitizing Agents; D011166:Porphyrins; D026082:Singlet Oxygen
keywords: HT29 cells; cancer; photodynamic therapy; photosensitizers; porphyrins