Product Overview and Chemical Structure

Cy5 PEG Biotin (SKU: C163500) is a dual-functional polyethylene glycol (PEG) derivative combining the near-infrared (NIR) fluorescent Cy5 dye with a terminal biotin group. The PEG backbone confers excellent aqueous solubility and biocompatibility, while the Cy5 chromophore provides strong, easily detectable fluorescence in the near-infrared window. The biotin terminus enables specific, high-affinity binding to streptavidin or avidin, facilitating versatile conjugation strategies across a wide range of biological and materials science applications.

The product is readily identifiable by its characteristic blue color in solution, simplifying visual confirmation of successful labeling or surface coating procedures.

Fluorescence Properties and Detection

Cy5 PEG Biotin exhibits a maximum absorption at 650 nm and an emission maximum at approximately 670 nm, placing it firmly within the near-infrared spectral range. This NIR fluorescence profile offers several practical advantages for biological research:

• Reduced autofluorescence: Biological samples typically exhibit minimal autofluorescence in the NIR region, resulting in high signal-to-noise ratios.
• Deeper tissue penetration: NIR light penetrates biological tissues more effectively than visible wavelengths, supporting in vivo and ex vivo imaging applications.
• Compatibility with standard instruments: Cy5 is compatible with widely available confocal microscopes, flow cytometers, and fluorescence scanners equipped with red laser lines (typically 633–647 nm).

The strong fluorescence intensity of the Cy5 label facilitates sensitive detection even at low concentrations, making this derivative well-suited for tracking in complex biological matrices.

Bioconjugation Applications

The bifunctional design of Cy5 PEG Biotin makes it a versatile reagent for a broad spectrum of research applications. The biotin moiety provides a well-established handle for attachment to streptavidin- or avidin-coated surfaces, nanoparticles, proteins, and antibodies via the strong non-covalent biotin–streptavidin interaction (K_d ~10⁻¹⁵ M). Key application areas include:

• Nanoparticle surface functionalization: Coating nanoparticles with Cy5 PEG Biotin simultaneously imparts steric stabilization (via PEG), NIR fluorescence traceability (via Cy5), and biotin-mediated targeting or further conjugation capability.
• Drug delivery research: Fluorescently labeled PEG shells on drug carriers enable real-time tracking of carrier biodistribution and cellular uptake.
• Biosensor development: The biotin group facilitates immobilization on streptavidin-functionalized sensor surfaces for assay development.
• Cell and tissue imaging: Cy5 PEG Biotin can be used to label cell surfaces or extracellular matrices for fluorescence microscopy studies.

The PEG spacer between the Cy5 dye and the biotin group reduces steric hindrance and maintains flexibility, helping to preserve the binding activity of both functional moieties.

Handling, Storage, and Preparation Guidelines

To ensure optimal performance of Cy5 PEG Biotin, the following handling and storage practices are recommended:

• Storage: Store lyophilized or solid product at −20 °C, protected from light. The Cy5 chromophore is susceptible to photobleaching upon prolonged exposure to ambient light.
• Reconstitution: Dissolve in an appropriate aqueous buffer (e.g., phosphate-buffered saline, pH 7.4) or an organic solvent compatible with your downstream application. Vortex gently and verify dissolution by visual inspection of the characteristic blue color.
• Working solutions: Prepare working solutions fresh or in small aliquots stored at −20 °C to minimize repeated freeze-thaw cycles.
• Avoid oxidizing conditions: Minimize exposure to strong oxidizing agents that could degrade the Cy5 chromophore or the PEG backbone.

Always consult the product-specific Certificate of Analysis (CoA) for lot-specific purity data and recommended storage conditions prior to use.