Light-induced decomposition of indocyanine green

Invest Ophthalmol Vis Sci. 2008 May;49(5):1777-83. doi: 10.1167/iovs.07-0911.


Purpose: To investigate the light-induced decomposition of indocyanine green (ICG) and to test the cytotoxicity of light-induced ICG decomposition products.

Methods: 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.

Results: 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.

Conclusions: 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.

MeSH terms

  • Animals
  • Cell Survival / drug effects
  • Chromatography, High Pressure Liquid
  • Coloring Agents / metabolism
  • Coloring Agents / radiation effects*
  • Coloring Agents / toxicity
  • Indocyanine Green / metabolism
  • Indocyanine Green / radiation effects*
  • Indocyanine Green / toxicity
  • Lasers
  • Light*
  • Mass Spectrometry
  • Oxidation-Reduction
  • Photochemotherapy
  • Pigment Epithelium of Eye / drug effects
  • Pigment Epithelium of Eye / pathology
  • Singlet Oxygen / metabolism
  • Sodium Azide / pharmacology
  • Sunlight
  • Swine
  • Trypan Blue


  • Coloring Agents
  • Singlet Oxygen
  • Sodium Azide
  • Trypan Blue
  • Indocyanine Green