art indocyanine green cyanobenzothiazole icg cbt


 190.00 1215.00

Labeling via cysteine click chemistry

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The non-invasive near-infrared (NIR) fluorescence imaging dye Indocyanine green (ICG) is approved by the United States Food and Drug administration (FDA) for ophthalmologic angiography to determine cardiac output and liver blood flow and function. This dye is also used in cancer patients for the detection of solid tumors, localization of lymphnodes, and for angiography during reconstructive surgery, visualization of retinal and choroidal vasculature, and photodynamic therapy1-3. In cancer diagnostics and therapeutics, ICG could be used as both an imaging dye and a hyperthermia agent.

ICG is a tricarbocyanine-type dye with NIR-absorbing properties (peak absorption around 800 nm) and emission maximum at 807 nm (10% v/vDMSO/PBS). Little absorption in the visible range accounts for the low autofluorescence, tissue absorbance, and scattering at NIR wavelengths (700-900 nm).

The 2-cyanobenzothiazole (CBT) labeling procedure is based on the biocompatible click-reaction between 2-cyanobenzothiazole moiety and any 1, 2- or 1, 3- aminothiols (e.g. free or N-terminal cysteine)

This click reaction is 3 orders of magnitude faster than commonly used Staudinger ligation and offers the opportunity to develop optimal conjugates. Cyanobenzothiazole (CBT) active groups provide an efficient and convenient way to site-selectively link ICG dyes to 1,2- or 1,3-aminothiols on various substrates (Antibodies[1], peptides, proteins, nucleic-acid, small molecule drugs etc.) without any additional activation. The labeling reaction with aminothiols is selective over reaction with simple thiols.

The CBT click chemistry can be used together with all other biocompatible click reactions (like azide, alkyne, triphenylphosphine, tetrazine etc.), as it is very selective.

In addition in ICG-CBT labeling procedure no side product is formed as here is no leaving group (unlike NHS esters).

Material Amount Storage Stability
ICG-CBT 1 mg
  • -20° C
  • Desiccate
  • Protect from light
When stored as directed, reactive probes are stable for at least 3 months
5 mg
10 mg

Immediately before use, dissolve the ICG-CBT dye in anhydrous dimethylsulfoxide (DMF). Once reconstituted, this reactive probe solution is somewhat unstable, especially when exposed to light and oxugen.

If possible avoid nucleophilic bases, as they will partially degrade ICG core structure to non-NIR-fluorescent by-products and also react with CBT moiety to form unreactive products.

[1] It has been reported that conjugation to some antibodies may cause decrease in fluorescence intensity of ICG bound to antibody due to the formation of H-dimers.4 However, fluorescence is restored after cell binding and internalization, which can be used to design an activatable NIR fluorescent probe. Fluorescence intensity of the unbound ICG-antibody conjugate can be dramatically increased (up to 50-fold) by addition of SDS and β-mercaptoethanol, which diminishes π- π stacking5.
Experimental labeling procedures are described in detail6, 7.

  1. Schaafsma B.E. The clinical use of indocyanine green as a near-infrared fluorescent contrast agent for image-guided oncologic surgery. Surg. Oncol. 2011, 104, 323-332
  2. Saxena V, Sadoqi M, Shao J. Degradation kinetics of indocyanine green in aqueous solution. Pharm. Sci. 2003, 92, 2090
  3. Yaseen MA, Yu J, Wong MS, Anvari B. Stability assessment of indocyanine green within dextran-coated mesocapsules by absor- bance spectroscopy. Biomed. Opt. 2007, 12, 064031
  4. Ogawa, M., Kosaka, N., Choyke, P. L., Kobayashi, H. H-Type Dimer Formation of Fluorophores: A Mechanism of Activatable In Vivo Optical Molecular Imaging ACS Chem. Biol. 2009, 4(7), 535-546
  5. Ogawa, M., Kosaka, N., Choyke, P. L., Kobayashi, H. In vivo Molecular Imaging of Cancer with a Quenching Near-Infrared Florescent Probe Using Conjugates of Monoclonal Antibodies and Indocyanine Green Cancer Res. 2009, 69(4), 1268-1272
  6. Ren, H., Xiao, F., Zhan, K., Kim, Y.-P., Xie, H., Xia, Z., Rao, J. A Biocompatible Condensation Reaction for the Labeling of Terminal Residues on Proteins Chem. Int. Ed. 2009, 48, 9658-9662
  7. Nhuyen, D. P., Elliott, T., Holt, M., Muir, T. W., Chin, J. Genetically Encoded 1,2-Aminthiols Facilitate Rapid and Site-Specific Protein Labeling via a Bio-orthogonal Cyanobenzothiazole Condensation Am. Chem. Soc. 2011, 133, 11418-11421

Dark green powder



Product Size

1 kit

Detection Method

Fluorescence, optoacoustic

Excitation Class

Near infrared, NIR

Excitation/Emission maximum (nm)


Molecular Weight

931.38 g.mol-1



Shipping Condition


Regulatory Statement

For Research Use Only. Not for use in diagnostic procedures.


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