Streptavidin Colloidal Gold for Lateral Flow (AU2017) is a ready-to-use streptavidin colloidal gold conjugate built on 40 nm gold nanoparticles and supplied at 10 OD for biotin-based lateral flow assays. Each 1 mL vial comes with 50 mL of RNase-free lateral flow running buffer optimized for streptavidin–biotin binding, so you can run biotinylated oligonucleotides, antibodies or proteins on dipsticks without a conjugation step.
A proprietary surface chemistry attaches streptavidin robustly while keeping the colloid stable, avoiding the protein desorption and aggregation often seen with passively adsorbed conjugates and supporting better shelf life and reproducibility.
Key Features
- 40 nm gold nanospheres: diameter 40.0 ± 2.5 nm with an SPR peak at 534 ± 1 nm, a common particle size for visual lateral flow readouts.
- 10 OD, ready to use: no conjugation step needed; add the gold directly to your running buffer or conjugate pad workflow.
- High-affinity capture: streptavidin binds biotin with a Kd of roughly 10⁻¹⁴ to 10⁻¹⁵ M, so biotinylated targets stay bound for the length of the run.
- Matched running buffer included: 50 mL of RNase-free running buffer (pH 7.6) optimized for streptavidin–biotin interactions.
- Lot-to-lot consistency: narrow particle size distribution, consistent optical density and reliable binding activity across batches.
- Functionally tested: the lot spec sheet reports the measured SPR peak, optical density and a dipstick performance test.
Specifications
Each streptavidin colloidal gold order includes:
- Conjugate: 1 mL of 10 OD, 40 nm streptavidin-functionalized gold nanospheres (equivalent amount), ready to use
- Running buffer: 50 mL RNase-free lateral flow running buffer, pH 7.6
- Particle diameter: 40.0 ± 2.5 nm
- SPR peak: 534.0 ± 1 nm
- Conjugate pH: 7.6
- Storage: 2–8 °C, away from light. Do not freeze.
- SKU: AU2017
Larger volumes (the product listing shows 10 mL and 100 mL of 10 OD) and custom formulations are available on request from sales@attogene.com.
Who It’s For
This conjugate suits researchers and developers who want a reliable gold label without making their own conjugates:
- Labs building nucleic acid lateral flow (NALF) readouts for biotin-labeled amplicons, probes or oligonucleotides
- Assay developers testing line chemistry, stoichiometry and running conditions before scale-up
- Teams scaling a prototype who need consistent gold from batch to batch
How to Use Streptavidin Colloidal Gold in Your Assay
The spec sheet gives a general dipstick guide for biotinylated oligonucleotides:
- Bring the gold to room temperature and shake vigorously for about 30 seconds. Confirm visually that all particles are re-dispersed; if particulates remain, sonicate for up to 5 minutes at a time, shake and repeat as needed.
- Add 100–200 µL of running buffer to a well.
- Add about 5 µL of the 10 OD gold to the well.
- Add about 1 pmol of biotinylated oligonucleotide.
- Insert the dipstick and let the assay run for 10–15 minutes, then read the lines.
If you need to dilute the particles, the spec sheet suggests 150 mM PBS with 0.01% Tween-20, pH 7.4. For spraying or spotting onto conjugate pads, contact Attogene for recommendations. See the AU2017 spec sheet (PDF) for full handling details.
Performance and Quality Control
In the current lot’s functional test, dipsticks with anti-Dig and anti-FAM test lines and a biotin-BSA control line were run for 15 minutes with 5 µL of gold and 150 µL of running buffer. Biotin–digoxigenin and biotin–FAM oligonucleotides gave signal on their matching test lines at every amount tested, from 500 fmol down to 1 fmol, and the no-target control showed the control line only.
Visible particulates or a change in color or intensity can indicate aggregation; the spec sheet recommends filtering through a 0.45 µm or smaller PVDF filter and confirming quality by spectrophotometry and electron microscopy.
Balancing Stoichiometry
Line intensity depends on the ratio of biotinylated target to gold. In Attogene’s technical note on the Universal Lateral Flow Assay Kit (Strep-Gold), test line signal rose with added dual-labeled oligonucleotide, peaked near 1 pmol and then fell as excess free biotinylated target saturated the streptavidin. A similar peak was seen with biotinylated rabbit IgG, so titrate your target against a fixed amount of gold to find the best working range.
For pre-made strips, the Strep-Gold kit pairs this chemistry with sprayed dipsticks, and the Universal Lateral Flow Assay Kit (anti-FAM/FITC-Gold) uses an anti-FAM gold label instead. Related labels include Anti-FITC/FAM Colloidal Gold, Goat Anti-Rabbit Colloidal Gold, Goat Anti-Mouse Colloidal Gold and Protein A Colloidal Gold.
Frequently Asked Questions
What size and concentration is this streptavidin colloidal gold?
It uses 40 nm gold nanospheres (40.0 ± 2.5 nm) at 10 OD with an SPR peak at 534 nm. The current lot measured 10.25 OD.
Is running buffer included?
Yes. Each 1 mL of gold ships with 50 mL of RNase-free lateral flow running buffer (pH 7.6) optimized for streptavidin–biotin interactions.
How should I store it?
Store at 2–8 °C, away from light. Do not freeze: freezing causes irreversible aggregation. Particles can settle, so shake well before each use.
Can I use it with biotinylated antibodies as well as oligonucleotides?
Yes. The conjugate captures any biotinylated molecule. Attogene’s technical note shows streptavidin colloidal gold used with biotinylated rabbit IgG as well as biotin-labeled oligonucleotides.
Has it been used in published work?
Yes. Attogene’s streptavidin 40 nm 10 OD gold appears in the lateral flow immunoassay section of Waller L et al., “High sensitivity, rapid detection of virus in high traffic environments,” Frontiers in Bioengineering and Biotechnology, 2022;10:877603 (doi: 10.3389/fbioe.2022.877603).
Can Attogene help develop my assay?
Yes. For custom formulations or full assay development, see Attogene’s lateral flow development services.
For research use only. Not for use in diagnostic procedures. Questions? Call 512-333-1330 or email sales@attogene.com.
Streptavidin 40 nm 10 OD Colloidal Gold was featured in the Lateral Flow Immunoassay section of the paper.
