Kinetics of singlet oxygen photosensitization in human skin fibroblasts

• Published in: Free radical biology & medicine Vol. 44; no. 11; pp. 1926 - 1934
• Main Authors: Jiménez-Banzo, Ana, Sagristà, M. Luisa, Mora, Margarita, Nonell, Santi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2008
• Subjects: Cell Proliferation; Cells, Cultured; Darkness; Diffusion; Fibroblasts; Fibroblasts - drug effects; Fibroblasts - radiation effects; Humans; Kinetics; Light; Microscopy, Phase-Contrast; Near infrared; Photodynamic therapy; Photosensitizer; Photosensitizing Agents - pharmacology; Porphyrin; Porphyrins - pharmacology; Singlet oxygen; Singlet Oxygen - pharmacology; Skin - drug effects; Skin - radiation effects; Subcellular Fractions; Subcellular localization; Time resolved; A; C; DMSO; G; 1O 2; D-PBS; MTT; BSA; DMEM; T; Φ Δ; TPPS; Fibroblasts; Diffusion; PBS; PDT; Time resolved; sens; SDS; Photodynamic therapy; EDTA; TMPyP; Near infrared; Singlet oxygen; Porphyrin; DNA; NIR; τ Δ; τ T; ROS; Subcellular localization; Kinetics; Photosensitizer
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2008.02.011

The roles played by singlet oxygen ( 1O 2) in photodynamic therapy are not fully understood yet. In particular, the mobility of 1O 2 within cells has been a subject of debate for the last two decades. In this work, we report on the kinetics of 1O 2 formation, diffusion, and decay in human skin fibroblasts. 1O 2 has been photosensitized by two water-soluble porphyrins targeting different subcellular organelles, namely the nucleus and lysosomes, respectively. By recording the time-resolved near-IR phosphorescence of 1O 2 and that of its precursor the photosensitizer's triplet state, we find that the kinetics of singlet oxygen formation and decay are strongly dependent on the site of generation. 1O 2 photosensitized in the nucleus is able to escape out of the cells while 1O 2 photosensitized in the lysosomes is not. Despite showing a lifetime in the microsecond time domain, 1O 2 decay is largely governed by interactions with the biomolecules within the organelle where it is produced. This observation may reconcile earlier views that singlet oxygen-induced photodamage is highly localized, while its lifetime is long enough to diffuse over long distances within the cells.