title: Red versus blue light illumination in hexyl 5-aminolevulinate photodynamic therapy: the influence of light color and irradiance on the treatment outcome in vitro.
abstract: Hexyl 5-aminolevulinate (HAL) is a lipophilic derivative of 5-aminolevulinate, a key intermediate in biosynthesis of the photosensitizer protoporphyrin IX (PpIX). The photodynamic efficacy and cell death mode after red versus blue light illumination of HAL-induced PpIX have been examined and compared using five different cancer cell lines. LED arrays emitting at 410 and 624 nm served as homogenous and adjustable light sources. Our results show that the response after HAL-PDT is cell line specific, both regarding the shape of the dose-survival curve, the overall dose required for efficient cell killing, and the relative amount of apoptosis. The ratio between 410 and 624 nm in absorption coefficient correlates well with the difference in cell killing at the same wavelengths. In general, the PDT efficacy was several folds higher for blue light as compared with red light, as expected. However, HAL-PDT₆₂₄ induced more apoptosis than HAL-PDT₄₁₀ and illumination with low irradiance resulted in more apoptosis than high irradiance at the same lethal dose. This indicates differences in death modes after low and high irradiance after similar total light doses. From a treatment perspective, these differences may be important.
authors.affiliation: Norwegian University of Science and Technology, Faculty of Medicine, Department of Cancer Research and Molecular Medicine, Erling Skjalgssons gate 1, Trondheim 7491, Norway.
authors.forename: Linda
authors.initials: L
authors.lastname: Helander
authors.affiliation: Norwegian University of Science and Technology, Faculty of Medicine, Department of Cancer Research and Molecular Medicine, Erling Skjalgssons gate 1, Trondheim 7491, Norway.
authors.forename: Hans E
authors.initials: HE
authors.lastname: Krokan
authors.affiliation: Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, Department of Physics, Høgskoleringen 5, Trondheim 7491, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Johnsson
authors.affiliation: Norwegian University of Science and Technology, Faculty of Medicine, Department of Cancer Research and Molecular Medicine, Erling Skjalgssons gate 1, Trondheim 7491, Norway.
authors.forename: Odrun A
authors.initials: OA
authors.lastname: Gederaas
authors.affiliation: University of Salzburg, Division of Physics and Biophysics, Department of Materials Science and Physics, Laboratory of Photodynamic Inactivation of Microorganisms, Hellbrunnerstraße 34, Salzburg 5020, Austria.
authors.forename: Kristjan
authors.initials: K
authors.lastname: Plaetzer
mesh_terms: D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003116:Color; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008029:Lighting / Q000379:methods*; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000473:pathology*; D010778:Photochemotherapy / Q000379:methods*; D011829:Radiation Dosage; D016896:Treatment Outcome
chemical_list: D000622:Aminolevulinic Acid