title: Photophysical and photobiological properties of a sulfonated chlorin photosensitiser TPCS(2a) for photochemical internalisation (PCI).
abstract: This study investigated the photophysical and photobiological properties of a new amphiphilic chlorin photosensitiser, disulfonated tetraphenylchlorin (TPCS(2a)), for photochemical internalisation (PCI). The absorption and fluorescence spectra of TPCS(2a) were examined in a range of solvents together with fluorescence lifetime measurements. The fluorescence lifetime of TPCS(2a) was found to be 8.5 ns in methanol, whereas non-exponential decays were observed in distilled water due to sensitiser dimerisation. The singlet oxygen quantum yield of TPCS(2a) was determined as 0.62 in deuterated methanol by direct observation of singlet oxygen phosphorescence. In a human oral squamous carcinoma (HN5) cell line, intracellular co-localisation of TPCS(2a) and Alexa488-labelled saporin, a macromolecular toxin, was observed corresponding predominantly to a lysosomal distribution. Intracellular fluorescence redistribution of TPCS(2a) and Alexa488-saporin was observed after 405 nm irradiation. Using two-photon confocal microscopy at 840 nm, and fluorescence lifetime imaging (FLIM), the lifetime was measured as 6 ns in HN5 cells. PCI using TPCS(2a) was shown to be very effective, and a synergistic increase in saporin toxicity was achieved in HN5 cells where viability was significantly reduced after light exposure compared to saporin (25 nM) treatment alone. The results demonstrate the favourable photophysical and photobiological properties of TPCS(2a) for PCI, which induces the relocalisation of a macromolecular anti-cancer toxin inside cells and significantly enhances cell death.
authors.affiliation: National Medical Laser Centre, Division of Surgery and Interventional Science and Institute for Biomedical Engineering, University College London, 67-73 Riding House Street, London W1W 7EJ, United Kingdom. tzu-wen.wang@kcl.ac.uk
authors.forename: Julie T-W
authors.initials: JT
authors.lastname: Wang
authors.forename: Kristian
authors.initials: K
authors.lastname: Berg
authors.forename: Anders
authors.initials: A
authors.lastname: Høgset
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Bown
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: MacRobert
mesh_terms: D001692:Biological Transport; D045744:Cell Line, Tumor; D006258:Head and Neck Neoplasms / Q000473:pathology; D006801:Humans; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism*; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism*; D054789:Ribosome Inactivating Proteins, Type 1 / Q000378:metabolism; D000076985:Saporins; D026082:Singlet Oxygen / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D054789:Ribosome Inactivating Proteins, Type 1; C559366:meso-tetraphenyl chlorin disulphonate; D026082:Singlet Oxygen; D000076985:Saporins