ICG Maleimide | CAS 2143933-81-5

ICG Maleimide is a maleimide-functionalized derivative of indocyanine green (ICG) designed for rapid thiol-directed bioconjugation. The maleimide group enables coupling to cysteine-containing peptides, proteins, and thiol-bearing biomolecules, while the near-infrared fluorescence of the ICG scaffold supports noninvasive optical readouts in molecular imaging and fluorescence-based assays. This reagent is commonly used to build fluorescent conjugates for labeling, tracking, and probe construction where NIR emission and stable conjugate formation are required.

1. Protein And Peptide Labeling

ICG Maleimide is used by protein engineering and chemical biology groups to generate NIR fluorescent conjugates from cysteine-containing proteins, antibodies, antibody fragments, and peptides. Researchers typically incorporate the dye into labeling workflows for binding studies, reagent characterization, and fluorescence-based tracking of biomolecular distribution. The maleimide handle provides a straightforward route to attach the fluorophore to thiol groups introduced by site-directed cysteine design or by thiol-releasing strategies used in bioconjugation pipelines. Resulting ICG conjugates are frequently employed in optical imaging experiments and fluorescence readouts where near-infrared signal is advantageous for reducing background from visible wavelengths.

2. Fluorescent Probe Construction

ICG Maleimide is a key building block for constructing NIR fluorescent probes used in molecular imaging reagent development and assay prototyping. Teams developing targeted or modular probes often use the maleimide functionality to attach ICG to recognition elements such as engineered ligands, cysteine-functional scaffolds, or thiol-bearing components that later serve as the recognition or delivery module. The resulting conjugates support fluorescence visualization and quantitative optical measurements in microscopy and plate-based assays, particularly when NIR excitation/emission is preferred for improved tissue or background contrast in relevant experimental setups. This makes ICG Maleimide useful for creating conjugate libraries that can be screened for labeling performance and imaging behavior in reagent development programs.

3. Biomaterial Surface Functionalization

ICG Maleimide is applied in biomaterials science to functionalize surfaces and prepare fluorescently traceable materials by coupling the dye to thiol-containing coatings, linkers, or surface-modified biomolecule layers. Research groups working on hydrogels, polymer composites, and engineered interfaces use the maleimide chemistry to incorporate NIR fluorescence into material platforms for tracking, localization, and workflow validation. In these applications, ICG Maleimide enables incorporation of the fluorophore into a defined surface chemistry context, supporting optical monitoring of material behavior and conjugate stability during experimental handling. The NIR fluorescence of the ICG scaffold is particularly useful for distinguishing labeled materials from autofluorescent backgrounds in imaging and analytical readouts.

4. NIR Imaging Conjugates

ICG Maleimide is employed to prepare NIR fluorescent conjugates for whole-sample and macroscopic fluorescence imaging workflows where indocyanine green emission provides strong signal in the near-infrared window. Imaging-focused laboratories use thiol-maleimide labeling to generate fluorescent constructs from cysteine-bearing biomolecules, enabling visualization of distribution patterns in experimental imaging studies and fluorescence quantification. The reagent's bioconjugation functionality supports consistent incorporation of the fluorophore into complex labeling mixtures used for optical tracking and comparative imaging experiments. This approach is commonly used when researchers need NIR-compatible fluorescent labeling reagents that can be generated rapidly from thiol-containing components.