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polymethine dye

IC Green, Indocyanine green, Foxgreen
Empirical Formula (Hill Notation):
CAS Number:
Molecular Weight:
EC Number:
MDL number:
PubChem Substance ID:

Quality Level




Dye content, ~85%


diagnostic assay manufacturing

storage temp.

room temp

SMILES string




InChI key


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General description

Cardiogreen is a negatively charged polymethine dye that forms noncovalent fluorescent complexes with proteins. This "pseudofluorogenic" property has been utilized for protein determination by capillary electrophoresis with diode laser-induced fluorescence detection.


Cardiogreen has been used to resolve several labeled proteins including: human serum albumin, ribonuclease A, transferrin, and cytochrome c.
Cardiogreen has been used as an intraocular capsular stain. It has been used in the dye-dilution method for cardiac output.


25, 50, 100 mg in glass bottle
Bottomless glass bottle. Contents are inside inserted fused cone.

Analysis Note

solubility: 0.01g in 10mL H2O : green to very dark green


Exclamation mark

Signal Word


Hazard Statements

Hazard Classifications

Eye Irrit. 2 - Skin Irrit. 2 - STOT SE 3

Target Organs

Respiratory system

Storage Class Code

13 - Non Combustible Solids



Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Personal Protective Equipment

dust mask type N95 (US),Eyeshields,Gloves

Certificate of Analysis

Certificate of Origin

  1. How does the storage temperature relate to shipping conditions?

    The storage conditions that a Sigma-Aldrich catalog and label recommend for products are deliberately conservative. For many products, long-term storage at low temperatures will increase the time during which they are expected to remain in specification and therefore are labeled accordingly. Where short-term storage, shipping time frame, or exposure to conditions other than those recommended for long-term storage will not affect product quality, Sigma-Aldrich will ship at ambient temperature. The products sensitive to short-term exposure to conditions other than their recommended long-term storage are shipped on wet or dry ice. Ambient temperature shipping helps to control shipping costs for our customers. At any time, our customers can request wet- or dry-ice shipment, but the special handling is at customer expense if our product history indicates that the product is stable for regular shipment. See Shipping and Storage for more information.

  2. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  3. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

  4. How do I find price and availability?

    There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote.  USA customers:  1-800-325-3010 or view local office numbers.

  5. What is the Department of Transportation shipping information for this product?

    Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product. 

  6. Has Cardiogreen been used for in vivo optical imaging studies?

    We do not subject this product to in vivo testing. However, one study documents the use of the product in a study with mice:For optical imaging, mice were injected intravenously with a mixture of 0.05 ml of 260 μM ICG (Cardiogreen) and 0.05 ml of 360 μM DTR (70,000 MW, Invitrogen) in saline (equivalent to 0.4 mg per kg or 7.4 μM initial concentration in blood).

  7. Does Cardiogreen dissolve equally well in saline and in water?

    Each lot is tested for solubility in hot water at 1 mg/mL. We have found that Sigma Product No. I2633 (which has the same CAS number as Product No. 21980) dissolves in water at 1 mg/mL without heating. Further dilute in saline to prepare an isotonic solution.

  8. How long can I store a solution of Cardiogreen after it has been prepared?

    Sigma-Aldrich recommends that solutions be prepared fresh and not stored. Solutions "are stable only for a few hours and cannot be kept overnight." See: Sigma-Aldrich Handbook of Dyes, Stains, and Indicators, Green, F. ed., p. 407.

  9. Can Product No. I2633, Cardiogreen, be used as a biological stain?

    Limited absorbance in the visible region practically precludes the use of Indocyanine Green as a biological stain. See: Sigma-Aldrich Handbook of Dyes, Stains, and Indicators, Green, F. ed., p. 407.

  10. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

E M McCorquodale et al.
Electrophoresis, 22(12), 2403-2408 (2001-08-25)
Indocyanine green (ICG)--a negatively charged, polymethine dye--can interact noncovalently with proteins to form fluorescent complexes, with excitation and emission maxima near 780 and 820 nm, respectively. This behavior was realized utilizing either a 100 mM phosphate buffer or a 25
Aqueous Angiography with Fluorescein and Indocyanine Green in Bovine Eyes.
Huang AS et al.
Translational vision science & technology, 5, 5-5 (2016)
Mixed S-nitrosylated polymerized bovine hemoglobin species moderate hemodynamic effects in acutely hypoxic rats.
Irwin D et al.
American Journal of Respiratory Cell and Molecular Biology, 42, 200-200 (2010)
Ran Tivony et al.
Journal of biomedical nanotechnology, 10(6), 1041-1048 (2014-04-23)
In this paper we describe the preparation of novel Near Infrared (NIR) fluorescent nanoparticles for application in medical imaging of colorectal tumors. The nanoparticles are prepared by using only non-covalent binding processes of molecules which are approved for clinical use.
Toshiki Endo et al.
Journal of neurosurgery. Spine, 18(5), 443-449 (2013-03-12)
The characteristics and efficacy of indocyanine green (ICG) videoangiography in cavernous malformation (CM) have not been fully elucidated. The purpose of this paper is to examine the potential utility of ICG videoangiography in the surgical treatment of intramedullary CMs. The

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