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Indocyanine Green (ICG) Dyes

Indocyanine Green (ICG) Dyes

— High-Performance Near-Infrared Fluorescent Dyes Empowering Imaging and Phototherapy Research

Indocyanine Green (ICG) dyes are a class of organic fluorescent dyes with near-infrared (NIR) absorption and emission properties, widely used in cutting-edge fields such as biomedical imaging, drug delivery monitoring, and photothermal/photodynamic therapy. Their excellent optical performance, biocompatibility, and tissue penetration ability make them essential functional molecular probes in both research and clinical settings.

As a professional supplier of photochemical products, Alfa Chemistry offers a variety of ICG dyes with different specifications and structural modifications, designed to meet diverse research needs related to imaging performance, stability, and conjugation activity.

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Key Properties of ICG Dyes

Indocyanine Green dyes possess unique molecular structures and optical characteristics, providing unparalleled advantages in research and medical imaging. Key features include:

Near-Infrared Absorption and Emission

ICG efficiently absorbs NIR light around 780 nm and emits fluorescence within 800–850 nm. This spectral window avoids biological tissue autofluorescence interference and offers excellent tissue penetration, suitable for deep-tissue imaging and in vivo monitoring.

Superior Tissue Penetration

Compared to visible-light dyes, NIR dyes like ICG penetrate biological tissues over longer distances, from millimeters to centimeters, enabling high-demand applications such as tumor margin identification and lymphatic imaging.

Good Biocompatibility and Safety

ICG is FDA-approved for human injection, exhibiting low toxicity and good biodegradability. It demonstrates excellent safety profiles in most animal and human studies.

High Sensitivity and Low Background Noise

The emission wavelength avoids autofluorescence regions, significantly enhancing signal-to-noise ratio. This makes ICG ideal for high-sensitivity imaging tasks such as micro-lesion localization and blood flow tracking.

Strong Chemical Modifiability

Alfa Chemistry supplies various ICG derivatives functionalized with NHS esters, carboxyl groups, maleimides, etc., facilitating conjugation with antibodies, proteins, and polymer carriers to build multifunctional probes and nanoplatforms.

Good Water Solubility and Dispersibility

Some ICG sodium salt products exhibit excellent water solubility, convenient for direct use in cell assays, animal injections, and clinical simulation environments.

Typical Applications

With the advancement of near-infrared fluorescence technology, ICG dyes have become core tools in multiple research and clinical areas. Key application fields and examples include:

Near-Infrared Fluorescence Imaging (NIRF Imaging)

ICG serves as a fluorescent contrast agent for dynamic monitoring of physiological or pathological processes, including:

In vivo animal imaging: studying drug delivery pathways, tissue-specific distribution, and disease progression;
Lymphatic imaging and surgical navigation: sentinel lymph node identification during cancer surgery;
Cerebral blood flow imaging: observing microvascular flow speed through cranial windows;
Liver function assessment: intravenous injection of ICG to monitor metabolic clearance rates.

Photothermal Therapy (PTT)

ICG absorbs NIR light and converts it to heat, inducing targeted tissue hyperthermia. It is a widely used photosensitizer for tumor photothermal therapy. When combined with carriers such as gold nanoparticles or liposomes, it improves targeting and heat conversion efficiency.

Applied in breast cancer, melanoma, pancreatic cancer, and other solid tumors;
Can be combined with MRI or photoacoustic imaging to enable multimodal therapy.

Photodynamic Therapy (PDT)

Under specific conditions, ICG acts as a photosensitizer to trigger oxidative stress responses, generating reactive oxygen species (ROS) that damage tumor cells. It is especially suitable for skin and gastrointestinal cancers.

Often combined with nanodrug delivery systems to improve local accumulation;
Combined with immunotherapy to enhance synergistic effects.

Smart Nanomaterial Construction and Delivery Systems

ICG dyes can be coupled with polymers, proteins, graphene, and biodegradable carriers to build nanoprobes with targeting, responsiveness, and theranostic functions:

Construction of integrated “targeting + imaging + therapy” nanoplatforms;
Intelligent tumor-site responsive release and fluorescence tracking;
Development of implantable/injectable microsystems for disease management.

Customers Often Look For

To support various research directions and technical demands, Alfa Chemistry has selected hot-selling Indocyanine Green (ICG) products helping users efficiently conduct NIR imaging and therapy research.

Indocyanine Green | CAS 3599-32-4

ICG Alkyne | CAS 1622335-41-4

ICG Carboxylic acid | CAS 181934-09-8

ICG NHS Ester | CAS 1622335-40-3

ICG Maleimide | CAS 2143933-81-5

Indocyanine Green | CAS 3599-32-4

Product Description: Standard ICG dye with excellent near-infrared fluorescence performance, a classic choice for NIR in vivo imaging and photothermal studies.
Recommended Applications: Blood flow imaging, liver function assessment, in vivo animal tracking
Packaging: 1 mg, 5 mg, 10 mg

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ICG Alkyne | CAS 1622335-41-4

Product Description: ICG Alkyne is a derivative introducing an alkyne functional group on the ICG structure, enabling copper-catalyzed azide-alkyne cycloaddition (CuAAC) for efficient conjugation with azide compounds.
Recommended Applications: Construction of fluorescently labeled nanomaterials, biomacromolecule modification, imaging probe synthesis
Reactive Group: Terminal alkyne (–C≡CH)
Advantages: Compatible with various bioorthogonal labeling systems, with good chemical selectivity and imaging stability

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ICG Carboxylic acid | CAS 181934-09-8

Product Description: Featuring a terminal carboxyl group, suitable for conjugation with amine-containing molecules, ideal for nanoparticle construction and targeted probe preparation.
Recommended Applications: Nanoparticle construction, bioconjugation, composite probe synthesis
Modification Site: Carboxyl (-COOH)
Advantages: High chemical reactivity, suitable for further modification and functional integration

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ICG NHS Ester | CAS 1622335-40-3

Product Description: NHS ester form of ICG, reacts rapidly with proteins, antibodies, peptides while retaining fluorescence activity.
Recommended Applications: Immunofluorescence labeling, targeted drug delivery systems
Advantages: High conjugation efficiency, good stability, suitable for various biological samples

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ICG Maleimide | CAS 2143933-81-5

Product Description: Contains maleimide reactive group, selectively reacts with thiol groups (-SH), used to build functional probes or bioresponsive systems.
Recommended Applications: Thiol-modified protein conjugation, enzyme labeling assays, targeted imaging development
Applicable Platforms: Protein engineering, biomaterials, molecular imaging

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Our Support to You

High purity guaranteed

Suitable for demanding research experiments

Comprehensive data support

Includes COA, HPLC chromatograms, UV-Vis spectra, and other technical documentation

Multiple specifications

Flexible procurement for laboratory-scale or pilot-scale needs

Fast delivery and responsive after-sales

Supports global shipping, custom development, and technical consultation

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Why Choose Alfa Chemistry’s ICG Dyes?

Focused on high-end photochemical products for research and industry
Extensive product range covering the entire ICG series and other near-infrared dyes
Experienced technical team offering full-process support
Supporting numerous universities, research institutes, and companies worldwide in successful projects

What Success Stories Can We Share?

Discover how our products are applied in real-world scenarios through our case studies.

Case 1: Efficient Water-Soluble NIR Imaging Probe Construction for Inflammation Marker Protein Tracking

Product

Disulfo-ICG Maleimide

Research Direction: Targeted protein labeling for near-infrared real-time imaging system development

Background

A Swedish bioengineering lab is developing a NIR imaging system to monitor inflammation marker proteins in vivo. They selected recombinant proteins with thiol groups as targets and urgently needed a NIR fluorescent dye that could conjugate efficiently and stably to thiols.

Procurement & Usage

Researchers sourced Disulfo-ICG Maleimide from Alfa Chemistry and utilized its maleimide group for selective conjugation with protein –SH groups, constructing targeted ICG probes. The probes showed excellent water solubility and high labeling efficiency, achieving high-contrast imaging of target proteins in mouse inflammation models. Patent applications are underway.

Customer Feedback

"We highly appreciate this product’s water solubility and labeling efficiency. It perfectly matches our requirements for fast and clear imaging."

Case 2: Click Chemistry-Modified Dual-Modal Probe for Precise Tumor In Vivo Imaging

Product

ICG Azide

Research Direction: Construction of multimodal molecular probes and targeted tumor imaging

Background

A U.S. medical school’s nanomedicine team is developing dual-modal imaging (NIRF+MRI) probes. They needed to conjugate ICG to carrier molecules via click chemistry for precise optical signal control.

Procurement & Usage

The team chose Alfa Chemistry’s ICG Azide and connected it to alkyne-functionalized magnetic nanoparticles via CuAAC click chemistry, building a smart probe with both fluorescence and magnetic resonance imaging capabilities. In breast cancer models, the probe showed excellent tumor accumulation and image contrast.

Customer Feedback

"ICG Azide exhibits stable reactivity and high purity, suitable for efficient conjugation in complex systems. It’s an indispensable core component in our molecular probe design."

Case 3: Covalent Labeling of ICG in Visualized Hydrogel Systems for Tissue Regeneration Research

Product

ICG Dichlorotriazine

Research Direction: Fluorescent functionalized hydrogels for tissue engineering and in vivo tracking

Background

A Japanese materials science university is developing NIR-visualized hydrogels for soft tissue regeneration, requiring covalent incorporation of ICG dyes into hydrogel backbones containing hydroxyl or amino groups to enable in vivo imaging and biocompatibility studies.

Procurement & Usage

Researchers purchased ICG Dichlorotriazine from Alfa Chemistry and utilized its reactive dichlorotriazine group to form stable covalent bonds with amino groups in hydrogels, achieving fluorescent functionalization. The constructed ICG hydrogels promoted tissue repair in rabbit muscle defect models and allowed non-invasive optical tracking.

Customer Feedback

"ICG Dichlorotriazine’s strong covalent labeling ability and preserved fluorescence properties open new directions for our materials engineering applications."

Frequently Asked Questions (FAQs)

Q1: How to choose among ICG derivatives (such as Azide, Maleimide, Dichlorotriazine) for bioconjugation reactions?

The choice depends on the functional groups present on the target molecule:

For biomolecules containing thiol groups (–SH), Maleimide-type ICG is recommended, which forms selective covalent bonds via Michael addition.
If the molecule to be modified contains an alkyne group (–C≡CH), ICG Azide can be used for efficient coupling via CuAAC click chemistry.
For target molecules with primary amine (–NH₂) or hydroxyl (–OH) groups, Dichlorotriazine-type ICG is suitable for nucleophilic substitution reactions to form stable covalent bonds.

Q2: How to assess whether ICG derivatives retain fluorescence activity after conjugation?

It is recommended to compare the UV-Vis absorption spectra and fluorescence emission spectra of samples before and after conjugation, focusing on shifts or quenching of the absorption peak (~780 nm) and emission peak (~810–830 nm). Additionally, HPLC purity analysis and fluorescence quantum yield measurements can be used to evaluate whether the dye maintains near-infrared imaging capability after conjugation.

Q3: What is the stability of ICG derivatives in aqueous solutions or PBS buffer? Are they suitable for long-term storage?

Most ICG derivatives are sensitive to light and heat in pure water or PBS. It is advised to store them protected from light at low temperatures (below –20°C) and to prepare fresh solutions before use. For water-soluble products (e.g., Disulfo-ICG), UV detection before and after use is recommended to confirm activity. For ICG dissolved in organic solvents, avoid repeated freeze-thaw cycles and extreme pH conditions.

Q4: When using ICG click chemistry reagents (such as ICG Azide), how to control nonspecific binding or cross-reactions?

It is recommended to limit the reaction time (usually less than 2 hours), perform inert gas purging to prevent oxidation, and use Cu(I) catalysts along with appropriate ligands (e.g., THPTA) to enhance selectivity. To avoid nonspecific background signals, dialysis or chromatographic purification should be performed after conjugation to remove unreacted dye molecules.

Q5: Can ICG derivatives be used to construct multifunctional nanoplatforms? What advantages do they have over traditional dyes?

Yes. ICG derivatives can form stable conjugates with nanomaterials (such as liposomes, polymers, metal nanoparticles) via their active functional groups, providing near-infrared visualization capability. Compared to traditional fluorescent dyes, ICG offers:

Deeper tissue penetration
Lower biological autofluorescence interference
Better suitability for constructing in vivo theranostic platforms (combined therapy and diagnostics)

Latest Updates

Stay informed with the latest updates from our company, where we continually innovate and enhance our services to meet your needs.

Knowledge & Learning

Overview of the Application of Indocyanine Green (ICG) as a Medical Dye

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