ICG Sulfo-NHS ester

ICG Sulfo-NHS ester is a near-infrared, sulfonated cyanine dye activated as an NHS ester for efficient amide coupling to primary amines on proteins, peptides, and other biomolecules. Its water-compatible sulfonate groups and strong NIR fluorescence make it a widely used labeling reagent for optical tracking, imaging reagent development, and fluorescence-based assays where reduced background from visible autofluorescence is advantageous.

1. Protein Conjugation Labeling

ICG Sulfo-NHS ester is commonly used by protein chemistry and chemical biology teams to generate fluorescent protein conjugates for optical readouts in microscopy, plate-based fluorescence, and imaging workflows. The NHS ester reacts with lysine side-chain primary amines under standard bioconjugation conditions, enabling straightforward preparation of dye-labeled antibodies, enzymes, binding proteins, and protein standards. Researchers often choose this reagent when they need a water-soluble NIR fluorophore for labeling while maintaining compatibility with fluorescence imaging systems that detect near-infrared emission.

2. Antibody and Affinity Reagent Imaging

ICG Sulfo-NHS ester supports preparation of NIR fluorescent affinity reagents used to visualize binding and distribution in cell-based and materials-based studies. Antibody conjugates, receptor-binding protein conjugates, and other affinity constructs prepared with NHS-activated dye are frequently applied in fluorescence imaging experiments to follow targeting behavior on cell surfaces or within biomaterial environments. Because the dye is delivered as an activated ester, conjugation can be tuned for labeling workflows that require stable amide linkage formation between the dye and the biomolecule.

3. Biomaterial Surface Functionalization

ICG Sulfo-NHS ester is also used in biomaterials science to introduce fluorescent tagging onto amine-bearing surfaces and polymers for tracking material localization and coating uniformity. By coupling to primary amines present on functionalized hydrogels, polymer backbones, or surface-modified substrates, researchers can generate NIR fluorescent coatings for microscopy and imaging validation. This application is particularly useful in experimental setups where NIR fluorescence provides improved contrast against common background signals from biological media and where fluorescent labeling needs to remain covalently attached to the material.

4. Fluorescent Tracing Assay Development

ICG Sulfo-NHS ester is frequently incorporated into fluorescence assay development and reagent screening workflows that rely on NIR signal for monitoring labeled components. Teams developing fluorescence-based binding assays, uptake or transport readouts, and tracer experiments use the NHS ester to prepare dye-labeled biomolecular probes that can be quantified by fluorescence instrumentation. The sulfonated, NIR-emitting format helps support assay designs where NIR detection reduces interference from visible-range autofluorescence, improving the practicality of optical readouts in complex sample matrices.