Photophysical properties of a photocytotoxic fluorinated chlorin conjugated to four beta-cyclodextrins

• Type: Article in International Scientific Journal
• Date: 2008

Authors

Silva, JN (Author) Other; Silva, AMG (Author) Other; Tome, JP (Author) Other; Ribeiro, AO (Author) Other; Domingues, MRM (Author) Other; Cavaleiro, JAS (Author) Other; Silva, AMS (Author) Other; Graca, M (Author) Other; Neves, MGPMS (Author) Other; Tome, AC (Author) Other; Serra, OA (Author) Other; Bosca, F (Author) Other; Filipe, P (Author) Other; Santuse, R (Author) Other; Morliere, P (Author) Other

Journal

Title: Photochemical & Photobiological Sciences

Vol. 7

Pages: 834-843

ISSN: 1474-905X

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 35 Citations

Scopus - 35 Citations

Other information

Authenticus ID: P-004-4D8

DOI: 10.1039/b800348c

Abstract (EN): 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 similar to 8 ns. This interaction is destroyed upon addition of Triton X100 to buffer. Both FC and CDFC strongly fluoresce (Phi(F) similar to 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 mu s 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 (similar to 35 000 M(-1) cm(-1)) leads to an estimate of similar to 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).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10