title: Photophysical properties of a photocytotoxic fluorinated chlorin conjugated to four beta-cyclodextrins.
abstract: A meso-tetrakis(pentafluorophenyl)-chlorin with the reduced pyrrole ring linked to an isoxazolidine ring (FC) has been conjugated to four beta-cyclodextrins (CDFC). The CDFC exhibits excellent water solubility and is a potent photosensitizer towards proliferating NCTC 2544 human keratinocytes. The study by conventional steady state absorption and fluorescence spectroscopies and by time-resolved femto- and nanosecond laser flash spectroscopies suggests that in ethanol and pH 7 buffer the beta-cyclodextrins embed the highly hydrophobic tetrakis(pentafluorophenyl)-chlorin macrocycle and strongly interact with the chlorin rings in the singlet and triplet manifolds. In these solvents, femtosecond spectroscopy suggests that the conjugate undergoes a rapid relaxation in the upper excited singlet states induced by photochemical and/or conformation change(s) at a rate of about 5 ps(-1) to fluorescent states whose lifetime is approximately 8 ns. This interaction is destroyed upon addition of Triton X100 to buffer. Both FC and CDFC strongly fluoresce (Phi(F) approximately 0.5) in micelles. Similar behavior is observed at the triplet level. In ethanol and water, the initial transient triplet state absorbance decays within 1-3 mus yielding a longer lived triplet with spectral properties indistinguishable from that of original difference absorbance spectra. The determination of the molar absorbance in the 440-460 nm region ( approximately 35 000 M(-1) cm(-1)) leads to an estimate of approximately 0.2 for the triplet formation quantum yield of FC in toluene and of FC and CDFC in Triton X100 micelles. Quenching of the CDFC triplets by dioxygen in buffer produces (1)O(2) in a good yield consistent with the effective photocytotoxicity of the chlorin-cyclodextrins conjugate towards cultured NCTC 2544 human keratinocytes. By contrast, FC which aggregates in buffer produces little if any (1)O(2).
authors.affiliation: Universidade de Lisboa, Faculdade de Medicina, Clínica Universitária de Dermatologia, 1699, Lisboa, Portugal.
authors.forename: João Nuno
authors.initials: JN
authors.lastname: Silva
authors.forename: Ana M G
authors.initials: AM
authors.lastname: Silva
authors.forename: João P
authors.initials: JP
authors.lastname: Tomé
authors.forename: Anderson O
authors.initials: AO
authors.lastname: Ribeiro
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
authors.forename: José A S
authors.initials: JA
authors.lastname: Cavaleiro
authors.forename: Artur M S
authors.initials: AM
authors.lastname: Silva
authors.forename: M Graça P M S
authors.initials: MG
authors.lastname: Neves
authors.forename: Augusto C
authors.initials: AC
authors.lastname: Tomé
authors.forename: Osvaldo A
authors.initials: OA
authors.lastname: Serra
authors.forename: Francisco
authors.initials: F
authors.lastname: Bosca
authors.forename: Paulo
authors.initials: P
authors.lastname: Filipe
authors.forename: René
authors.initials: R
authors.lastname: Santus
authors.forename: Patrice
authors.initials: P
authors.lastname: Morlière
mesh_terms: D000042:Absorption; D000818:Animals; D002417:Cattle; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity; D011166:Porphyrins / Q000737:chemistry*; D026082:Singlet Oxygen / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014867:Water / Q000378:metabolism; D047392:beta-Cyclodextrins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D047392:beta-Cyclodextrins; D014867:Water; D026082:Singlet Oxygen; C006969:chlorin