Indocyanine Green (ICG) | CAS 3599-32-4 | USP | 95.8%

Product Name: Indocyanine Green (ICG)
CAS No.: 3599-32-4
MF: C₄₃H₄₇N₂NaO₆S₂
Purity: 95.8%
Standard: USP

Description

Indocyanine Green (ICG) is a synthetic cyanine dye widely used in medicine and biomedical research due to its unique optical and pharmacokinetic properties. It is used for measuring cardiac output and assessing liver function. Due to its ability to absorb and emit light in the near-infrared (NIR) range, ICG is applied for blood flow imaging, liver function evaluation, angiography, and other diagnostic procedures.

1. Introduction

Indocyanine Green was developed for non-invasive tissue imaging and vascular assessment. Its applications span both clinical research and advanced methods of surgical navigation and photodynamic therapy. Due to its high biocompatibility and stable optical characteristics, ICG remains one of the most sought-after agents for non-invasive diagnostics.

2. Chemical Structure & Synthesis

ICG belongs to the tricarbocyanine class and is typically used as a sodium salt.

• Molecular Formula: C₄₃H₄₇N₂NaO₆S₂

• Approximate Molecular Weight: 775 g/mol

The structure of ICG includes a branched conjugated π-system core consisting of conjugated double bonds, which is responsible for light absorption in the near-infrared spectrum. The synthesis involves condensation of aromatic compounds and formation of a cyanine core, followed by introduction of functional groups that ensure water solubility and binding to plasma proteins.

3. Physicochemical Properties

Optical Characteristics:

• Absorption Peak: Approximately 780–805 nm in aqueous solution

• Fluorescence Peak: Approximately 820–835 nm

These properties allow ICG to be effectively used for deep optical imaging, as near-infrared light has high tissue penetration.

Solubility: ICG is readily soluble in water, making it convenient for intravenous administration.

Photosensitivity: Like most dyes, ICG is light-sensitive. Solutions should be protected from bright light to prevent photodegradation.

Protein Binding: When introduced into the bloodstream, ICG rapidly binds to plasma albumin, affecting its distribution, short circulation time, and hepatic excretion.

4. Applications in Medicine & Research

4.1 Clinical Diagnostics

Liver Function Assessment: ICG is used for clearance testing to evaluate liver functional status. Rapid binding to plasma proteins and biliary excretion make it an effective indicator of hepatic function.

Angiography & Ophthalmology: Due to its near-infrared fluorescence properties, ICG is used for visualization of retinal and choroidal vessels, as well as for studying peripheral vessels in various tissues.

Surgical Navigation & Lymphography: ICG is used for tumor margin delineation, lymph node mapping, and blood flow monitoring during surgical procedures, contributing to improved surgical precision.

4.2 Biotechnology Research & Nanotechnology

Fluorescence Microscopy: ICG is used for tissue and cell labeling, allowing tracking of biological agent distribution in vivo.

Nanoformulations: In targeted drug delivery research, ICG is conjugated with nanoparticles to improve imaging and control active substance release, opening new possibilities in photodynamic therapy.

5. Safety & Limitations

Biocompatibility: ICG has a confirmed safety profile for clinical use at recommended doses. However, some patients, especially those with hypersensitivity to iodine, may experience allergic reactions.

Pharmacokinetics: Rapid binding to plasma proteins and hepatic excretion require caution in patients with impaired liver function.

Photosensitivity: Due to light sensitivity, ICG solutions should be stored in darkened containers to prevent photodegradation, which may affect optical properties.

6. Future Perspectives

Current research is focused on expanding ICG applications, including:

• Photodynamic Therapy: Using ICG as a photosensitizer to generate cytotoxic radicals upon infrared irradiation

• Combined Diagnostic Methods: Integrating ICG with other imaging agents and computational methods for hybrid surgical guidance systems

• Novel Nanoconstructs: Developing innovative delivery systems to improve ICG stability, targeting, and fluorescence intensity

7. Conclusion

Indocyanine Green (ICG, CAS 3599-32-4) is an indispensable tool in modern medicine due to its unique optical characteristics and high biocompatibility. Its ability to efficiently absorb and emit light in the near-infrared range ensures high sensitivity of imaging methods, enabling diagnostics, liver function assessment, and surgical navigation with high precision. Despite some limitations related to pharmacokinetics and photosensitivity, ongoing research and innovative developments continue to open new perspectives for ICG use in both clinical practice and biomedical research.