Light-Induced Decomposition of Indocyanine Green

• Published in: Investigative ophthalmology & visual science Vol. 49; no. 5; pp. 1777 - 1783
• Main Authors: Engel, Eva, Schraml, Rudiger, Maisch, Tim, Kobuch, Karin, Konig, Burkhard, Szeimies, Rolf-Markus, Hillenkamp, Jost, Baumler, Wolfgang, Vasold, Rudolf
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01.05.2008; Association for Research in Vision and Ophtalmology
• Subjects: Animals; Biological and medical sciences; Cell Survival - drug effects; Chromatography, High Pressure Liquid; Coloring Agents - metabolism; Coloring Agents - radiation effects; Coloring Agents - toxicity; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Indocyanine Green - metabolism; Indocyanine Green - radiation effects; Indocyanine Green - toxicity; Lasers; Light; Mass Spectrometry; Medical sciences; Ophthalmology; Oxidation-Reduction; Photochemotherapy; Pigment Epithelium of Eye - drug effects; Pigment Epithelium of Eye - pathology; Singlet Oxygen - metabolism; Sodium Azide - pharmacology; Sunlight; Swine; Trypan Blue; Vertebrates: nervous system and sense organs; Light; Indocyanine green; Ophthalmology
• ISSN: 0146-0404; 1552-5783; 1552-5783
• DOI: 10.1167/iovs.07-0911

To investigate the light-induced decomposition of indocyanine green (ICG) and to test the cytotoxicity of light-induced ICG decomposition products. ICG in solution was irradiated with laser light, solar light, or surgical endolight. The light-induced decomposition of ICG was analyzed by high-performance liquid chromatography (HPLC) and mass spectrometry. Porcine retinal pigment epithelial (RPE) cells were incubated with the light-induced decomposition products of ICG, and cell viability was measured by trypan blue exclusion assay. Independent of the light source used, singlet oxygen (photodynamic type 2 reaction) is generated by ICG leading to dioxetanes by [2+2]-cycloaddition of singlet oxygen. These dioxetanes thermally decompose into several carbonyl compounds. The decomposition products were identified by mass spectrometry. The decomposition of ICG was inhibited by adding sodium azide, a quencher of singlet oxygen. Incubation with ICG decomposition products significantly reduced the viability of RPE cells in contrast to control cells. ICG is decomposed by light within a self-sensitized photo oxidation. The decomposition products reduce the viability of RPE cells in vitro. The toxic effects of decomposed ICG should be further investigated under in vivo conditions.