Carboxyl 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: Carboxyl (–COOH) surface groups are reactive functional groups that enable covalent coupling to primary amines (–NH₂) via EDC/NHS activation chemistry. The carboxyl group itself is not reactive without activation — it requires EDC (with optional Sulfo-NHS) to form an active NHS ester intermediate.

Why it matters:

• Enables coupling to lysine residues or N-terminus of antibodies and proteins — the most commonly used bioconjugation approach.
• Gives a stable, covalent amide bond between the particle surface and the target biomolecule.
• Activation step (EDC ± NHS) must be performed in amine-free buffer (pH 5.5–6.0 for EDC, pH 7.2–7.5 for coupling).
• Low non-specific binding after blocking with BSA or similar makes carboxyl beads well-suited for quantitative assays.

How to interpret here: This product has Carboxyl surface chemistry. Coupling requires EDC/NHS activation as described in the protocol (see Documents). Avoid Tris, glycine, or other amine-containing buffers during activation and coupling steps — they inactivate the NHS ester.

Tip: Add Sulfo-NHS along with EDC to stabilize the activated intermediate. This significantly improves coupling efficiency at neutral pH and longer incubation times.

What it means: Particle Size refers to the mean hydrodynamic diameter of the particle in suspension. Available sizes: 10 nm–5 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–5 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: Activated (Ready-to-conjugate) means the particle surface carries a reactive functional group (carboxyl, amine, NHS ester, maleimide, or azide) that is ready for coupling to your chosen biomolecule. A conjugation reaction step is required before the beads can capture targets.

Why it matters:

• Maximum flexibility: choose the biomolecule you conjugate based on your specific target and assay design.
• Coupling density can be optimized by adjusting protein:bead ratio during conjugation.
• Multiple coupling chemistries available depending on the specific surface group (see Surface Chemistry chip).
• Conjugation kits are available to simplify the workflow and reduce protocol development time.

How to interpret here: This product is Activated (Ready-to-conjugate). You will need to perform a coupling reaction to attach your specific antibody, protein, or oligonucleotide before use. Follow the coupling protocol in the Documents section; conjugation kits providing all required buffers are available separately.

Tip: Always test conjugation efficiency (e.g., by BCA assay on the supernatant after magnetic separation) before scaling up 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: MRI Imaging, Magnetic Particle Imaging, Drug Delivery, Diagnostics.

Why it matters:

• MRI Imaging: this product can directly support this workflow based on its surface chemistry and particle properties.
• Magnetic Particle Imaging: this product can directly support this workflow based on its surface chemistry and particle properties.
• Drug Delivery: 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 MRI Imaging, Magnetic Particle Imaging. 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.