Streptavidin Iron Oxide Nanoparticles

What it means: Iron Oxide Nanoparticles are colloidal superparamagnetic nanoparticles (typically 5–30 nm) composed of magnetite (Fe₃O₄) and/or maghemite (Fe₂O₃). At this size range they exhibit superparamagnetism — they magnetize in an applied field but retain no remanence when the field is removed.

Why it matters:

• Superparamagnetic behavior prevents particle aggregation between uses — key for stable aqueous dispersions.
• Nanoparticle size governs MRI relaxivity, circulation time in vivo, and cellular uptake behavior.
• Surface chemistry determines aqueous dispersibility, colloidal stability, and available conjugation strategies.
• Narrow size distribution (from thermal decomposition synthesis) gives more predictable and reproducible performance than co-precipitation methods.

How to interpret here: This product is an Iron Oxide Nanoparticle format. The selected surface group and particle size are the primary selectors for application fit. Review the specification sheet for zeta potential and colloidal stability data in your intended buffer system.

Tip: Colloidal stability depends strongly on buffer ionic strength and pH. Always test the particles in your specific assay buffer before scaling up.

What it means: Streptavidin is a tetrameric protein that binds biotin with one of the highest known non-covalent affinities in biology (Kd ≈ 10⁻¹⁵ M). Streptavidin is covalently coupled to the particle surface, making most of the four biotin-binding sites sterically available.

Why it matters:

• Captures any biotinylated molecule — antibodies, nucleic acids, peptides, small molecules, and ligands — without additional coupling reagents.
• Essentially irreversible binding under physiological conditions supports stable complex formation across washes.
• Covalent coupling prevents streptavidin leaching, ensuring consistent biotin-binding activity.
• Low non-specific binding surface reduces background in immunoassay and flow cytometry applications.

How to interpret here: This product has Streptavidin surface chemistry — it is pre-conjugated and ready to capture biotinylated targets directly. No additional activation is needed. Simply mix with your biotinylated ligand and magnetically separate.

Tip: The biotin–streptavidin bond is essentially irreversible at physiological pH. If you need reversible biotin capture (e.g., for elution), consider monomeric avidin or nitrated streptavidin variants with reduced affinity.

What it means: Particle Size refers to the mean hydrodynamic diameter of the particle in suspension. Available sizes: 10 nm–30 nm.

Why it matters:

• Nanoparticle size determines superparamagnetic relaxivity, surface area, and in vivo behavior.
• Smaller particles have higher surface area per mg — more binding sites per weight of material.
• Larger particles settle faster under gravity and separate faster with a magnet.
• Select size based on your magnetic separation speed requirements, surface area needs, and assay geometry.

How to interpret here: This product is available in 10 nm–30 nm. Smaller sizes remain suspended longer and provide more surface area per mg for conjugation or MRI contrast. Larger sizes separate faster with a magnet.

Tip: Particle size is measured by DLS (dynamic light scattering) and represents the hydrodynamic diameter, which includes surface coating — actual iron core size is smaller as shown in TEM measurements in the specification sheet.

What it means: Pre-conjugated means the binding ligand (streptavidin, Protein G, or another affinity ligand) has already been covalently coupled to the particle surface during manufacturing. No additional conjugation step is needed before use in your assay.

Why it matters:

• Ready-to-use for target capture immediately after resuspension — fastest path to assay results.
• Covalent ligand attachment prevents leaching or dissociation under assay conditions.
• Quality-controlled coupling ensures consistent binding capacity lot-to-lot.
• Saves time and reduces protocol variability compared to performing your own coupling.

How to interpret here: This product is Pre-conjugated. Simply resuspend (bath sonication recommended) and use directly in your capture protocol. No EDC, NHS, or crosslinker is needed. Confirm working concentration in your specific assay format.

Tip: Store at 2–8°C without freezing. Binding activity can be verified by a simple pull-down test using a known amount of biotinylated or IgG target before committing to full assay development.

What it means: Aqueous dispersion means this product is supplied as a colloidal suspension in an aqueous buffer (typically PBS, DI water, or a proprietary storage buffer). The particles are dispersed and ready for use in water-based biological applications without any solvent exchange step.

Why it matters:

• Compatible directly with cell culture media, PBS, HEPES, and other standard biological buffers.
• No solvent exchange or phase transfer required before use in aqueous assay protocols.
• Aqueous colloidal stability maintained by surface coating (polymer, PEG, or functional group layer).
• Bath sonication before use ensures complete resuspension after storage sedimentation.

How to interpret here: This product is in Aqueous dispersion. It can be used directly in your assay buffer after resuspension. Confirm compatibility with your specific buffer conditions (ionic strength, pH, protein concentration) by checking the product specification sheet or running a small-scale stability test.

Tip: High ionic strength buffers (>500 mM) or pH extremes outside the specification range may compromise colloidal stability. Always validate in your specific matrix.

What it means: Applications list the primary experimental workflows this product has been used for: Immunoassay, Nucleic Acid Isolation, Cell Separation, Immunoprecipitation.

Why it matters:

• Immunoassay: this product can directly support this workflow based on its surface chemistry and particle properties.
• Nucleic Acid Isolation: this product can directly support this workflow based on its surface chemistry and particle properties.
• Cell Separation: this product can directly support this workflow based on its surface chemistry and particle properties.

How to interpret here: This product is suited for the listed applications. The most relevant for this product are Immunoassay, Nucleic Acid Isolation. Review the application-specific protocol in the Documents section before beginning workflow development.

Tip: Application suitability depends on specific experimental conditions (buffer, sample matrix, target concentration). Always validate at pilot scale before full assay development.