title: Biochemical analysis and decomposition products of indocyanine green in relation to solvents, dye concentrations and laser exposure.
abstract: OBJECTIVE
  To investigate pH, ions, osmolarity and precipitation of indocyanine green (ICG), as well as the profile of ICG decomposition products (DPs) after laser exposure and the interaction with quenchers.
  
  
  METHODS
  ICG was diluted in water, 5% glucose (GL) or balanced salt solution (BSS) to achieve concentrations of 2.5, 1, 0.25 and 0.1 mg/ml. Osmolarity, pH and precipitation were analyzed immediately and after 24 h. Precipitation analyses were done with a scanning electron microscope. Anion and iodate analyses of ICG and infracyanine green (IfCG) were performed by capillary zone electrophoresis. With regard to DPs, 0.5 mg/ml of ICG was assessed with high-performance liquid chromatography (HPLC) after 810-nm laser irradiation. DP profiles were evaluated with ICG dilution in quenchers (Trolox, histidine and DABCO) in 3 concentrations (0.1, 1 and 10 M).
  
  
  RESULTS
  BSS promoted iso-osmotic ICG solutions of 208 mOsm (147-266) compared to GL with 177 mOsm. BSS solutions had a higher physiological pH of 7.2 compared with the GL one of 6.55. ICG precipitated more when diluted with BSS (5.95 mg); in contrast, GL showed less precipitate (3.6 mg). IfCG has no iodine derivates and other ICGs have an average 4.6% of iodate derivates. From HPLC analysis, 5 DPs were observed. The rate of DPs was higher when BSS was used (p < 0.05). Five DPs have been generated with ICG, and they may be altered with the quenchers DABCO, histidine and Trolox.
  
  
  CONCLUSIONS
  BSS dilution induces more precipitation and DPs. ICG dilution in any solvent induces DPs. Quencher use reduces the amount of toxic DPs.
authors.affiliation: Vision Institute IPEPO, Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil.
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Penha
authors.forename: Eduardo B
authors.initials: EB
authors.lastname: Rodrigues
authors.forename: Mauricio
authors.initials: M
authors.lastname: Maia
authors.forename: Carsten H
authors.initials: CH
authors.lastname: Meyer
authors.forename: Elaine de Paula Fiod
authors.initials: Ede P
authors.lastname: Costa
authors.forename: Eduardo
authors.initials: E
authors.lastname: Dib
authors.forename: Etelvino
authors.initials: E
authors.lastname: Bechara
authors.forename: Andréia
authors.initials: A
authors.lastname: Lourenço
authors.forename: Acácio A S
authors.initials: AA
authors.lastname: Lima Filho
authors.forename: Edna H
authors.initials: EH
authors.lastname: Freymüller
authors.forename: Michel Eid
authors.initials: ME
authors.lastname: Farah
mesh_terms: D000085:Acetates / Q000737:chemistry*; D011232:Chemical Precipitation; D002851:Chromatography, High Pressure Liquid; D004396:Coloring Agents / Q000737:chemistry* / Q000528:radiation effects*; D004338:Drug Combinations; D019075:Electrophoresis, Capillary; D006863:Hydrogen-Ion Concentration; D007208:Indocyanine Green / Q000737:chemistry* / Q000528:radiation effects*; D007834:Lasers; D008855:Microscopy, Electron, Scanning; D008903:Minerals / Q000737:chemistry*; D009994:Osmolar Concentration; D012965:Sodium Chloride / Q000737:chemistry*
chemical_list: D000085:Acetates; C030660:BSS solution; D004396:Coloring Agents; D004338:Drug Combinations; D008903:Minerals; D012965:Sodium Chloride; D007208:Indocyanine Green