AAT Bioquest


Product Image
Product Image
Gallery Image 1
Ordering information
Catalog Number
Unit Size
Add to cart
Additional ordering information
InternationalSee distributors
Bulk requestInquire
Custom sizeInquire
ShippingStandard overnight for United States, inquire for international
Request quotation
Physical properties
Molecular weight1427.73
Spectral properties
Correction Factor (280 nm)0.076
Extinction coefficient (cm -1 M -1)230000
Excitation (nm)789
Emission (nm)813
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure


Molecular weight
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Indocyanine green (ICG) is a cyanine dye used in medical diagnostics. It is used for determining cardiac output, hepatic function, and liver blood flow, and for ophthalmic angiography. It has a peak spectral absorption close to 800 nm. These infrared frequencies penetrate retinal layers, allowing ICG angiography to image deeper patterns of circulation than fluorescein angiography. Conventional activated ICG dye, ICG-Sulfo-OSu, has been used for preparing ICG-antibody conjugates utilized in in vivo imaging research as antibody conjugates. However, the ICG hydrophobicity often causes some unspecific bindings and antibody aggregation. The PEG12-modified ICG dyes are the most water-soluble ICG dyes. Their antibody conjugates shows better water solubility and significantly reducing unspecific binding.

Example protocol


Unless otherwise noted, all unused stock solutions should be divided into single-use aliquots and stored at -20 °C after preparation. Avoid repeated freeze-thaw cycles.

1. Protein stock solution (Solution A)
Mix 100 µL of a reaction buffer (e.g., 1 M  sodium carbonate solution or 1 M phosphate buffer with pH ~9.0) with 900 µL of the target protein solution (e.g. antibody, protein concentration >2 mg/mL if possible) to give 1 mL protein labeling stock solution. Note: The pH of the protein solution (Solution A) should be 8.5 ± 0.5. If the pH of the protein solution is lower than 8.0, adjust the pH to the range of 8.0-9.0 using 1 M  sodium bicarbonate solution or 1 M pH 9.0 phosphate buffer. Note: The protein should be dissolved in 1X phosphate buffered saline (PBS), pH 7.2-7.4. If the protein is dissolved in Tris or glycine buffer, it must be dialyzed against 1X PBS, pH 7.2-7.4, to remove free amines or ammonium salts (such as ammonium sulfate and ammonium acetate) that are widely used for protein precipitation. Note: Impure antibodies or antibodies stabilized with bovine serum albumin (BSA) or gelatin will not be labeled well. The presence of sodium azide or thimerosal might also interfere with the conjugation reaction. Sodium azide or thimerosal can be removed by dialysis or spin column for optimal labeling results. Note: The conjugation efficiency is significantly reduced if the protein concentration is less than 2 mg/mL. For optimal labeling efficiency the final protein concentration range of 2-10 mg/mL is recommended.

2. ICG-PEG12-OSu stock solution (Solution B)
Add anhydrous DMSO into the vial of ICG-PEG12-OSu to make a 10 mM stock solution. Mix well by pipetting or vortex. Note: Prepare the dye stock solution (Solution B) before starting the conjugation. Use promptly. Extended storage of the dye stock solution may reduce the dye activity. Solution B can be stored in freezer for two weeks when kept from light and moisture. Avoid freeze-thaw cycles.


This labeling protocol was developed for the conjugate of Goat anti-mouse IgG with ICG-PEG12-OSu. You might need further optimization for your particular proteins. Note: Each protein requires distinct dye/protein ratio, which also depends on the properties of dyes. Over labeling of a protein could detrimentally affects its binding affinity while the protein conjugates of low dye/protein ratio gives reduced sensitivity.

Run conjugation reaction
  1. Use 10:1 molar ratio of Solution B (dye)/Solution A (protein) as the starting point:  Add 5 µL of the dye stock solution (Solution B, assuming the dye stock solution is 10 mM) into the vial of the protein solution (95 µL of Solution A) with effective shaking. The concentration of the protein is ~0.05 mM assuming the protein concentration is 10 mg/mL and the molecular weight of the protein is ~200KD. Note: We recommend to use 10:1 molar ratio of Solution B (dye)/Solution A (protein). If it is too less or too high, determine the optimal dye/protein ratio at 5:1, 15:1 and 20:1 respectively.
  2. Continue to rotate or shake the reaction mixture at room temperature for 30-60 minutes. 

Purify the conjugation
The following protocol is an example of dye-protein conjugate purification by using a Sephadex G-25 column.
  1. Prepare Sephadex G-25 column according to the manufacture instruction.
  2. Load the reaction mixture (From "Run conjugation reaction") to the top of the Sephadex G-25 column.
  3. Add PBS (pH 7.2-7.4) as soon as the sample runs just below the top resin surface.
  4. Add more PBS (pH 7.2-7.4) to the desired sample to complete the column purification. Combine the fractions that contain the desired dye-protein conjugate. Note: For immediate use, the dye-protein conjugate need be diluted with staining buffer, and aliquoted for multiple uses. Note: For longer term storage, dye-protein conjugate solution need be concentrated or freeze dried. 


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of ICG-PEG12-OSu to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM70.041 µL350.206 µL700.413 µL3.502 mL7.004 mL
5 mM14.008 µL70.041 µL140.083 µL700.413 µL1.401 mL
10 mM7.004 µL35.021 µL70.041 µL350.206 µL700.413 µL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)Molecular weightVolume (Calculate)Concentration (Calculate)Moles


Open in Advanced Spectrum Viewer

Spectral properties

Correction Factor (280 nm)0.076
Extinction coefficient (cm -1 M -1)230000
Excitation (nm)789
Emission (nm)813

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Correction Factor (280 nm)Correction Factor (260 nm)
ICG Xtra-OSu7908142300000.0550.09



View all 5 citations: Citation Explorer
Comparison of Near-Infrared Imaging Agents Targeting the PTPmu Tumor Biomarker
Authors: Johansen, Mette L and Vincent, Jason and Rose, Marissa and Sloan, Andrew E and Brady-Kalnay, Susann M
Journal: Molecular Imaging and Biology (2023): 1--14
Assessment of Lexiscan for Blood Brain Barrier disruption to facilitate Fluorescence brain imaging
Authors: Pak, Rebecca W and Le, Hanh and Valentine, Heather and Thorek, Daniel and Rahmim, Arman and Wong, Dean and Kang, Jin U
Journal: (2017): ATu3B--2
Bioengineering of injectable encapsulated aggregates of pluripotent stem cells for therapy of myocardial infarction
Authors: Zhao, Shuting and Xu, Zhaobin and Wang, Hai and Reese, Benjamin E and Gushchina, Liubov V and Jiang, Meng and Agarwal, Pranay and Xu, Jiangsheng and Zhang, Mingjun and Shen, Rulong and others, undefined
Journal: Nature Communications (2016): 13306
Single-Layer MoS2 Nanosheets with Amplified Photoacoustic Effect for Highly Sensitive Photoacoustic Imaging of Orthotopic Brain Tumors
Authors: Chen, Jingqin and Liu, Chengbo and Hu, Dehong and Wang, Feng and Wu, Haiwei and Gong, Xiaojing and Liu, Xin and Song, Liang and Sheng, Zonghai and Zheng, Hairong
Journal: Advanced Functional Materials (2016)
Deep Photoacoustic/Luminescence/Magnetic Resonance Multimodal Imaging in Living Subjects Using High-Efficiency Upconversion Nanocomposites
Authors: Liu, Yu and Kang, Ning and Lv, Jing and Zhou, Zijian and Zhao, Qingliang and Ma, Lingceng and Chen, Zhong and Ren, Lei and Nie, Liming
Journal: Advanced Materials (2016)


View all 193 references: Citation Explorer
Ultrastaging of colon cancer by sentinel node biopsy using fluorescence navigation with indocyanine green
Authors: Hirche C, Mohr Z, Kneif S, Doniga S, Murawa D, Strik M, Hunerbein M.
Journal: Int J Colorectal Dis (2012): 319
Sentinel lymph node biopsy using real-time fluorescence navigation with indocyanine green in cutaneous head and neck/lip mucosa melanomas
Authors: Hayashi T, Furukawa H, Oyama A, Funayama E, Saito A, Yamao T, Yamamoto Y.
Journal: Head Neck (2012): 758
Efficacy of indocyanine green videography and real-time evaluation by FLOW 800 in the resection of a spinal cord hemangioblastoma in a child
Authors: Ueba T, Abe H, Matsumoto J, Higashi T, Inoue T.
Journal: J Neurosurg Pediatr (2012): 428
Concentration of indocyanine green does not significantly influence lymphatic function as assessed by near-infrared imaging
Authors: Aldrich MB, Davies-Venn C, Angermiller B, Robinson H, Chan W, Kwon S, Sevick-Muraca EM.
Journal: Lymphat Res Biol (2012): 20
Comparative Study of the Optical and Heat Generation Properties of IR820 and Indocyanine Green
Authors: Fern, undefined and ez-Fern, undefined and ez A, Manch and a R, Lei T, Carvajal DA, Tang Y, Zahid Raza Kazmi S, McGoron AJ.
Journal: Mol Imaging (2012): 99
Sentinel lymph node biopsy using a new indocyanine green fluorescence imaging system with a colour charged couple device camera for oral cancer
Authors: Iwai T, Maegawa J, Hirota M, Tohnai I.
Journal: Br J Oral Maxillofac Surg. (2012)
Usefulness of indocyanine green angiography to depict the distant retinal vascular anomalies associated with branch retinal vein occlusion causing serous macular detachment
Authors: Ueda T, Gomi F, Suzuki M, Sakaguchi H, Sawa M, Kamei M, Nishida K.
Journal: Retina (2012): 308
Application of indocyanine green videoangiography in surgery for spinal vascular malformations
Authors: Misra BK, Pur and are HR., undefined
Journal: J Clin Neurosci. (2012)
Indocyanine-Green Angiography Findings in Susac's Syndrome
Authors: Balaskas K, Guex-Crosier Y, Borruat FX.
Journal: Klin Monbl Augenheilkd (2012): 426
Gold nanomaterials conjugated with indocyanine green for dual-modality photodynamic and photothermal therapy
Authors: Kuo WS, Chang YT, Cho KC, Chiu KC, Lien CH, Yeh CS, Chen SJ.
Journal: Biomaterials (2012): 3270