Streptavidin Europium Chelate Microspheres for Lateral Flow are ready-to-use streptavidin europium microspheres for fluorescent lateral flow assays and other biotin-based detection formats. Each order provides 250 µL of a 1 mg/mL stock of europium-dyed polystyrene beads conjugated to streptavidin, with an excitation peak of 365 nm and an emission peak of 613 ± 10 nm, plus 50 mL of running buffer designed for these microspheres.
The beads carry a proprietary surface coating, and streptavidin is covalently conjugated to the particle. Every conjugate is functionally tested by lateral flow. Because streptavidin binds biotin with very high affinity, the microspheres can label biotin-tagged oligonucleotides and other biotinylated binders in your assay.
Key Features
- Europium fluorescence: excitation peak of 365 nm and emission peak of 613 ± 10 nm, per the specification sheet.
- 200 nm beads: particle size of 200 nm ± 10%.
- Covalent streptavidin coupling: streptavidin is covalently conjugated to the bead surface for stable biotin capture.
- Ready to use: supplied as a 1 mg/mL stock, so you can add it straight to your assay.
- Matched running buffer: 50 mL of lateral flow running buffer designed for these beads.
- Lateral flow tested: each conjugate is functionally tested in a lateral flow format.
Specifications
Each order of streptavidin europium microspheres includes:
- Streptavidin europium conjugate: 250 µL at 1 mg/mL
- Running buffer: 50 mL of lateral flow running buffer designed for Streptavidin Europium Chelate Microspheres
Conjugate specifications:
- Particle: europium-dyed polystyrene beads
- Particle size: 200 nm ± 10%
- Conjugate: streptavidin, covalently conjugated
- Excitation peak: 365 nm
- Emission peak: 613 ± 10 nm
- Solvent: 50 mM borate buffer, pH 8.3, with 0.05% ProClin 150 and 0.1% BSA
- Storage: 2–8 °C in a dark environment. Do not freeze.
You will also need: a biotin-labeled oligonucleotide or other biotinylated binder, lateral flow strips or another assay format, and a reader or imaging setup that can excite near 365 nm and detect emission near 613 nm. Larger volumes are available on request.
Who It’s For
This conjugate is built for assay developers who want a fluorescent label in place of a colored one. Typical users include:
- Teams developing fluorescent lateral flow assays for nucleic acid or protein targets that carry a biotin tag.
- Developers who want a red-emitting label with a wide gap between UV excitation (365 nm) and emission (613 nm).
- Researchers who already use streptavidin gold or streptavidin quantum dots and want to compare a europium readout on the same assay design.
How to Use Streptavidin Europium Microspheres in Your Assay
The specification sheet gives this starting guide for oligonucleotides:
- Bring the conjugate to room temperature and shake vigorously for 30 seconds so the particles are fully dispersed.
- Add 150–200 µL of the Europium Bead running buffer to your tube or well.
- Add 0.5–1 µL of the europium bead conjugate. If you dilute the beads, use 50 mM boric acid buffer, pH 8.3, with 0.1% BSA and 0.05% ProClin 150.
- Add 0.5–10 pmol of oligonucleotide.
- Run the strip. Run times range from 15 to 45 minutes, depending on the antigen and antibodies used.
To spray or spot the conjugate onto conjugate pads, contact sales@attogene.com for recommendations. Full details are in the streptavidin europium microspheres specification sheet (PDF).
Why Use a Europium Label?
Europium chelates are lanthanide complexes known for a narrow emission band and a long fluorescence lifetime. Loading many chelate molecules into a single polystyrene bead gives one bright label for each biotin binding event.
For a complete starting point, see the Fluorescent Universal Lateral Flow Assay Kit (Europium). For a visual readout, compare Streptavidin Colloidal Gold for Lateral Flow. Other fluorescent streptavidin labels include Streptavidin CdSe/ZnS Quantum Dots and Streptavidin R-Phycoerythrin.
Storage and Handling
- Store at 2–8 °C away from light. Storage at low temperature increases the shelf life and stability of the particles.
- Do not freeze. Freezing causes irreversible aggregation and destroys the product.
- Bring to room temperature and shake well before each use.
- If particulates or plating remain, sonicate in a sonicator bath for up to 5 minutes, shake and repeat as needed. Do not sonicate longer than 5 minutes at a time to limit heating.
- Visible particulates or a change in the color or intensity of the dispersion can mean the particles have aggregated. In that case, filter through a 0.45 µm polyvinylidene fluoride (PVDF) filter and keep the filtered product.
Frequently Asked Questions
What are the excitation and emission wavelengths?
The specification sheet lists an excitation peak of 365 nm and an emission peak of 613 ± 10 nm for these streptavidin europium microspheres.
What particle size and concentration are supplied?
The beads are 200 nm ± 10% and are supplied as 250 µL of a 1 mg/mL stock in 50 mM borate buffer, pH 8.3, with 0.05% ProClin 150 and 0.1% BSA.
How much conjugate should I use per test?
The starting guide uses 0.5–1 µL of streptavidin europium microspheres with 150–200 µL of running buffer and 0.5–10 pmol of oligonucleotide. Optimize these amounts for your own assay.
Can I freeze the conjugate?
No. Freezing causes irreversible particle aggregation. Store at 2–8 °C in the dark.
Can I spray the conjugate onto conjugate pads or order larger volumes?
Yes. Contact sales@attogene.com for conjugate pad spraying or spotting recommendations and for larger volumes.
For research use only. Not for use in diagnostic procedures. Questions? Call 512-333-1330 or email sales@attogene.com.
