Cy5-PEG5-azide

Cy5-PEG5-azide is a Cy5 fluorophore conjugated to a flexible polyethylene glycol (PEG) linker terminating in an azide handle, designed for copper-free or copper-mediated azide–alkyne click chemistry. As a fluorescent azide probe, it combines strong near-infrared imaging utility with the bioorthogonal labeling compatibility typically required for polymer, biomolecule, and surface functionalization workflows. The PEG spacer helps reduce steric constraints and improves accessibility of the azide group for downstream conjugation into labeled targets, including imaging reagents and functional materials.

1. Fluorescent Bioconjugation

Cy5-PEG5-azide is widely used to install a bright near-infrared fluorescent tag onto biomolecules and biomolecule-derived constructs via click-compatible coupling to alkyne-functional partners. Researchers use it for labeling antibodies, peptides, nucleic acid analogs, and protein scaffolds where a hydrophilic PEG spacer improves conjugation efficiency and reduces nonspecific surface interactions during incubation-based workflows. The Cy5 reporter enables sensitive tracking of labeled species in microscopy, flow-based assays, and gel-based characterization, while the azide functionality provides a modular “plug-in” handle for assembling multicomponent probes.

2. Surface And Material Labeling

Cy5-PEG5-azide supports fluorescent functionalization of polymers, nanoparticles, and material surfaces that have been engineered with complementary alkyne groups. In biomaterials research, the reagent is used to visualize coatings, hydrogel components, and scaffold architectures after click-based attachment, taking advantage of the PEG tether to promote uniform presentation of the dye away from the surface. This makes it particularly useful for mapping distribution, monitoring assembly steps, and generating traceable material building blocks for downstream composite fabrication and characterization.

3. Molecular Imaging Probes

Cy5-PEG5-azide is commonly incorporated into imaging probe libraries where azide–alkyne click chemistry is used to rapidly diversify probe structures around a Cy5 reporting motif. Molecular imaging groups use it to create fluorescent conjugates for optical readouts, including multivalent targeting constructs and imaging standards used for method development and instrument validation. The PEG5 linker provides a practical balance between dye brightness and conjugate flexibility, helping maintain probe accessibility when assembling larger architectures such as labeled nanoparticles, dendrimers, or multicomponent imaging platforms.

4. Diagnostic Reagent Development

Cy5-PEG5-azide is frequently used in the development of research diagnostic reagents that rely on fluorescent signal generation and modular conjugation strategies. Assay developers use the azide handle to attach Cy5 labels to capture elements such as affinity ligands, polymeric reporters, or solid-phase supports that have been functionalized with alkyne groups. The resulting fluorescent conjugates are then used to build and optimize detection workflows, including assay component screening, reagent stability studies, and standardized labeling controls for multiplexed readouts.