ICG-COOH | CAS 181934-09-8

Indocyanine Green carboxylic acid (ICG-COOH) is a near-infrared (NIR) fluorescent dye bearing a carboxyl group, enabling conjugation to amine- or hydrazide-functional biomolecules and incorporation into labeling workflows that benefit from reduced background autofluorescence. In research settings, ICG-COOH is used to build NIR fluorescent conjugates for optical imaging and fluorescence-based tracking, where its NIR emission is leveraged for deeper-tissue or low-background readouts relative to visible fluorophores.

1. NIR Fluorescent Labeling

ICG-COOH is widely used as a fluorescence labeling component for preparing NIR-tagged biomolecule conjugates, including protein and peptide labeling for imaging and binding studies. Researchers typically incorporate the dye into bioconjugates via the carboxyl functionality (commonly through coupling strategies to introduce the fluorophore onto amine-bearing targets), then quantify labeling by fluorescence readout and use the resulting conjugates in optical imaging experiments. This labeling approach is particularly common in workflows where NIR detection is preferred to minimize interference from visible-light fluorophores and to support imaging with NIR-capable plate readers, gel imagers, or optical imaging systems.

2. Fluorescence Imaging Tracers

ICG-COOH is used to generate NIR fluorescent tracers for microscopy and whole-sample fluorescence imaging, including studies that track distribution, uptake, and washout behavior of labeled materials. In chemical biology and biomaterials research, the dye is often appended to carriers such as nanoparticles, polymeric constructs, or surface-modified scaffolds to visualize localization and trafficking in experimental models using NIR excitation/emission detection. The carboxyl handle supports downstream conjugate construction, enabling researchers to tailor tracer chemistry for consistent labeling and to compare signal across experimental conditions using standardized imaging acquisition settings.

3. Biomaterial Surface Functionalization

ICG-COOH is frequently employed to fluorescently functionalize biomaterial surfaces and engineered materials for optical characterization and material tracking. Materials scientists and assay developers use the dye to coat or conjugate onto polymeric films, hydrogels, or other surfaces so that the resulting constructs can be visualized during processing, incubation, and imaging-based evaluation. The NIR emission supports monitoring in complex backgrounds, and the carboxyl group provides a practical chemical handle for integrating the dye into surface engineering workflows used in materials development and fluorescence readout assay development.