title: Characterization of a Squaraine/Chitosan System for Photodynamic Therapy of Cancer.
abstract: In this work, a squaraine dye CS5 was characterized and evaluated for its potential in photodynamic therapy. The studies were performed in ethanol and also in a powdered biopolymer, in this case chitosan. Ground state absorption, absolute fluorescence quantum yields, fluorescence lifetimes, and transient absorption were determined in order to evaluate the advantage of adsorbing the dye onto a biopolymer. Several concentrations of the dye, adsorbed onto chitosan, were prepared in order to evaluate the concentration effect on the photophysical parameters under study. A remarkable increase in the fluorescence quantum yield and lifetimes was detected when compared with the dye in solution. Also, a very clear dependence of the fluorescence quantum yield on the concentration range was found. A lifetime distribution analysis of these systems fluorescence evidenced the entrapment of the dye onto the chitosan environment with a monoexponential decay which corresponds to the monomer emission in slightly different environments. The transient absorption spectrum was obtained without sensitization indicating the existence of a triplet state which takes special importance in the generation of phototoxic species namely singlet oxygen. The subcellular localization of a photosensitizer is critical for efficient photoinduced cell death, in this way, colocalization studies were performed within HeLa cell line (human cervical carcinoma) through confocal microscopy. Toxicity in the dark and phototoxicity of CS5 were also evaluated for the same cellular model.
authors.affiliation: Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: Diana P
authors.initials: DP
authors.lastname: Ferreira
authors.affiliation: Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: David S
authors.initials: DS
authors.lastname: Conceição
authors.affiliation: Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Fernandes
authors.affiliation: Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Sousa
authors.affiliation: Mountain Research Centre (CIMO), ESA, Polytechnic Institute of Bragança , Campus de Santa Apolónia, 1172, 5301-855 Bragança, Portugal.
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Calhelha
authors.affiliation: Mountain Research Centre (CIMO), ESA, Polytechnic Institute of Bragança , Campus de Santa Apolónia, 1172, 5301-855 Bragança, Portugal.
authors.forename: Isabel C F R
authors.initials: IC
authors.lastname: Ferreira
authors.affiliation: Centro de Química-Vila Real, Universidade de Trás-os-Montes e Alto Douro , 5001-801 Vila Real, Portugal.
authors.forename: Paulo F
authors.initials: PF
authors.lastname: Santos
authors.affiliation: Centro de Química-Física Molecular and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: L F
authors.initials: LF
authors.lastname: Vieira Ferreira
mesh_terms: D000327:Adsorption; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002584:Cervix Uteri / Q000187:drug effects / Q000528:radiation effects; D048271:Chitosan / Q000737:chemistry*; D004396:Coloring Agents / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D003503:Cyclobutanes / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D004337:Drug Carriers / Q000737:chemistry*; D005260:Female; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D008027:Light; D010636:Phenols / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D010778:Photochemotherapy; D010782:Photolysis; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D014466:Ultraviolet Rays; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy*
chemical_list: D004396:Coloring Agents; D003503:Cyclobutanes; D004337:Drug Carriers; D010636:Phenols; D017319:Photosensitizing Agents; C480596:squaraine; D048271:Chitosan