title: Enhanced photodynamic effects using fractionated laser light.
abstract: Photodynamic eradication of tumour cells depends on the presence of a photosensitizer and light delivery to the cells. The present study investigated the influence of fractionated light (on-off mode) on cell killing as documented by a colony-forming assay. Photosensitizers were m-THPC (ethanol soluble, Foscan) and m-THPC-MD (water soluble, both from Scotia Pharmaceuticals, Guildford, UK). Fractionated laser light at a wavelength of 652 nm with a light duration of 0.05 s was more effective than continuous illumination at the same power density for both photosensitizers. We propose that fractionated laser light is more toxic due to short phases of recovery during the dark intervals, probably resulting in more singlet oxygen under these conditions. By use of Foscan, for example, and fractionated laser light, a similar effect is expected for the treatment of solid tumours. In this case we expect improvements in photodynamic therapy (PDT) for patients by lowering the concentrations of photosensitizer and/or by reducing the applied light dose.
authors.affiliation: Department of Gynaecology and Obstetrics, University Hospital, Zürich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Müller
authors.forename: H
authors.initials: H
authors.lastname: Walt
authors.forename: D
authors.initials: D
authors.lastname: Dobler-Girdziunaite
authors.forename: D
authors.initials: D
authors.lastname: Fiedler
authors.forename: U
authors.initials: U
authors.lastname: Haller
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D006801:Humans; D007834:Lasers; D008652:Mesoporphyrins / Q000494:pharmacology; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin