Indocyanine Green (ICG, IC Green, Foxgreen) is a negatively charged tricarbocyanine dye widely used for imaging and flow cytometry due to its low toxicity and near-infrared fluorescence emission.
ICG has an absorption maximum at 787 nm with slight absorption in the visible range and a fluorescence emission maximum at 819 nm. The minimal light scattering and low autofluorescence in this spectral range result in a significantly reduced background and improved signal-to-noise ratios, thereby enhancing detection sensitivity.
ICG maleimide is a thiol-reactive dye for labeling of protein SH groups, and it can be used to attach ICG fluorophore to proteins and peptides containing cysteine residues, as well as to other thiolated molecules (such as thiol-containing oligonucleotides). Cystines should be reduced with TCEP (tris-carboxyethylphosphine) or with another appropriate reductant prior to the labeling.
