Gold Colloid and Conjugates
Setting the Gold Standard for Nanoparticles
For three decades BBI has supplied the gold that powers more than 500 million diagnostic strips every year. making us the trusted partner for thousands of researchers, lateral flow assay developers and manufacturers worldwide.
World-renowned BBI Gold Colloid & Conjugates.
BBI’s optimized and proven production process yields citrate-capped nanospheres in sizes from 5nm up to 250nm with tight specifications in both size and %CV. This uniformity yields high batch-to-batch reproducibility, improving end-user manufacturability, reducing waste, and increasing speed to market. BBI’s large batch size, ISO-13485-certified manufacturing facility, and unparalleled quality results in a product with trusted performance year after year
Market-leading Gold Conjugates – Ready-to-run or Custom Solutions.
BBI specializes in conjugation to gold colloid. Choose from off-the-shelf conjugates or bespoke conjugation service to meet your individual needs – both backed by stringent QC and expert technical support
Colloids
| Product Name | Code | Type | Applications | |
|---|---|---|---|---|
| Gold Colloid: 20nm -100ml | EM.GC20/7 | Gold Colloid | Lateral Flow | Buy now |
| Gold Colloid: 40nm -100ml | EM.GC40/7 | Gold Colloid | Biosensing, Lateral Flow, Microarray | Buy now |
| Gold colloid: 60nm -100ml | EM.GC60/7 | Gold Colloid | Biosensing, Lateral Flow, Microarray | Buy now |
| Gold Colloid: 80nm -100ml | EM.GC80/7 | Gold Colloid | Biosensing, Lateral Flow, Microarray | Buy now |
Conjugates
| Product Name | Code | Type | Applications | |
|---|---|---|---|---|
| EM Grade 10nm BSA gold conjugate | EM.BSA10/2 | Gold Conjugate | Electron Microscopy | Buy now |
| EM Grade 15nm BSA gold conjugate | EM.BSA15/2 | Gold Conjugate | Electron Microscopy | Buy now |
| EM Grade 20nm BSA gold conjugate | EM.BSA20/2 | Gold Conjugate | Electron Microscopy | Buy now |
| EM Grade 40nm BSA gold conjugate | EM.BSA40/2 | Gold Conjugate | Electron Microscopy | Buy now |
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Gold Conjugate Starter Protocol
Protein conjugation can be complex, especially when developing a reproducible, scalable product.
Conjugation of proteins to gold depends upon three separate but dependent phenomena –
- Ionic attraction between negatively charged gold and positively charged protein
- Hydrophobic attraction between the protein and the gold surface
- Dative binding between the gold conducting electrons and sulphur atoms which may occur within amino
acids of the protein.
This protocol is a little bit of our expertise in a kit and is suitable for assessment of potential conjugation
conditions but is not necessarily suitable for production of conjugates at full manufacturing scale.
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Products & Services
Inside this catalog you’ll find one of the industry’s broadest collections of enzymes, antibodies, antigens, and more – meticulously developed to power world-class diagnostics and keep your pipeline moving.
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Reagents Range
Discover our collection of reagents covering a comprehensive range of biomarkers and applications for the IVD market, life sciences, cell culture and beyond.
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Frequently asked questions
Gold Colloid and Conjugates
How long is a gold colloid stable for?
The gold colloid will remain stable until at least the expiry date stated on the label if the colloid is kept unopened at the recommended storage temperature (2-8°C). BBI’s EM Grade gold colloids are assigned a 24-month expiry date from the date of manufacture. Stability was ascertained by real-time stability studies for the shelf life of the product.
How should the colloid be handled to maintain its stability?
For best results (to help avoid particle aggregation) you should avoid pipetting directly from the bottle. Instead you should pour out a small aliquot into a suitable container
(borosilicate glass is recommended) and pipette from this. This protects the bulk solution from cross-contamination and potential introduction of particulate matter (such as dust) which can cause particle aggregation. It is recommended that the bulk volume of gold colloid be kept in its original container.
What are the largest and smallest gold nanoparticles that BBI can make?
The smallest gold nanoparticle that BBI offers is 5nm in diameter and the largest is 250nm. The particle sizes available are: 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 60nm 80nm, 100nm, 150nm 200nm and 250nm.
What buffer is the colloid supplied in?
The gold nanoparticles are provided suspended in purified water (as made), with only residual chemicals left from manufacture also present in solution.
What are the key features and benefits of BBI’s gold colloids?
- BBI particles are proven stable for at least 24 months and are supplied with a minimum of three month’s expiry. Stable particles ensure a settled testing regime, saving you time and wastage
- Uniform shape and standard size with a low coefficient of variation. This ensures even antibody loading giving reliable results in your assay.
- Manufacturing scale. Batch sizes of up to 350+ litres to ensure you have a continuous supply.
How are the antibodies attached to the gold nanoparticle surface?
The antibodies are passively conjugated to the gold nanoparticle surface (no covalent or linker chemistry is used). Protein binds to gold colloid through amino acid residues: charge attraction (lysine), hydrophobic attraction (tryptophan), and sulphur bonding (cysteine).
What isotypes (classes) of antibody can be conjugated to gold nanoparticles?
IgG is the most popular isotype for conjugation and can be conjugated with a high success rate. The antibody binds to the gold nanoparticles through the Fc region, leaving the Fab region exposed and able to bind the antigen of interest. IgG3 antibodies are more difficult to work with so these should be avoided if possible.
IgM conjugations have a lower success rate. Cross-linking can occur when they are conjugated, and the Fc regions cannot always be exposed without damaging the integrity of the antibody.
IgE antibodies are raised in an allergic response, these antibodies can be conjugated to gold nanoparticles.
IgY antibodies are functionally similar to IgG antibodies and these can be conjugated to gold nanoparticles with a high success rate.
Antigen conjugations are possible, although the success rate is lower.
BBI can also conjugate other proteins, antibody fragments- Fab, Fc, ScFv and nanobodies.
What is the recommended storage temperature of the conjugates?
It is recommended to store the gold conjugates (BA Grade and Custom Conjugates) at 2-8°C. EM Grade conjugates can be kept frozen at -20°C for long term storage.
What do the various grades of conjugate (BA, CC, EM) available refer to?
BA refers to BioAssay. These conjugates are stock products which are routinely manufactured at BBI. These are most commonly used in lateral flow diagnostic tests. The particle size is 40nm.
CC refers to custom conjugates. These conjugates are similar to BA Grade conjugates but are usually manufactured on a custom basis by request of a customer. The particle size most commonly used is 40nm.
EM refers to Electron Microscopy. These conjugates are different to BA and CC conjugates, are usually made with smaller nanoparticles and are most often used in electron microscopy. The particle size most commonly used is 10nm.
EM refers to Electron Microscopy. These conjugates are different to BA and CC conjugates, are usually made with smaller nanoparticles and are most often used in electron microscopy. The particle size most commonly used is 10nm.
How dispersed are the conjugated gold nanoparticles?
Our gold nanoparticles have a high level of single particle dispersion.
40nm conjugates are tested using the MonoDispersity Index (MDI). MDI uses UV-Vis readings to assess the ratio achieved between the A520nm (absorbance at which 40nm OD readings are taken) and A600nm (associated with stability) of the conjugate. A pass/ fail criterion is assigned to the ratio which is deemed acceptable to produce a stable product.
Other gold nanoparticle sizes are assessed using Transmission Electron Microscope (TEM) to assess aggregation of the particles. This is a key indicator for the stability of the product.
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Delivering exceptional quality gold, time after time
With ≤5% odd shapes and a CV of ≤8%, the uniform shape and size of BBI gold ensures even antibody binding, giving reliable results in your assay.
View ProductsBBI particles are proven stable for at least twelve months and are supplied with a minimum of three month’s expiry. Stable particles ensure a settled testing regime, saving you time and wastage.
View ProductsOur batch sizes go up to 340l (40nm) to ensure you have a continuous supply.
View ProductsBBI gold must pass strict quality procedures before it's released to our customers, guaranteeing impressive performance characteristics at scale.
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Gold Colloid
Setting the Gold Standard for Nanoparticles
Every year our colloidal gold nanoparticles are used in over 500 million assays globally and are renowned for offering exceptional assay consistency levels. Our proprietary manufacturing technique allows for the production of large volume batches of gold to a high level of reproducibility of size, dispersion and shape, and we maintain this through tight quality control release specifications. This ensures a firm foundation for conjugation and peace of mind that your assay will provide reliable results.
BBI Solutions have been manufacturing high-quality gold nanoparticles for over 30 years, making us the trusted partner for thousands of researchers, lateral flow assay developers and manufacturers worldwide.
Gold Starter Packs
Are you using gold for the first time, or trying a new process and are unsure of which size particle to purchase? Our gold starter packs allow a comprehensive evaluation, comprising 100ml and/or 20ml each of a selection of our gold nanoparticles.
BBI Solutions gold nanoparticles for rapid diagnostic assays:
| 20nm Gold Nanoparticles | 40nm Gold Nanoparticles | 60nm Gold Nanoparticles | 80nm Gold Nanoparticles | |
|---|---|---|---|---|
| Average Diameter | 19.0 – 21.0nm | 37.0 – 43.0nm | 57.0 – 63.0nm | 77.0 – 85.0nm |
| Maximum acceptable % CV | 8% | |||
| Number of odd shapes per 100 particles | ≤5 | ≤10 | ≤10 | ≤10 |
| Optical density @520nm (using a 1 cm pathlength) | Bulk available at OD1 Up to 50mL available at OD 5/10 |
Bulk available at OD1 Bulk available at OD 4.5 – 5.0 Up to 50mL available at OD10 |
Bulk available at OD1 | Bulk available at OD1.0 at 555nm |
| Batch scale | Up to 110L at OD1 | Up to 340L at OD1 | Up to 64L at OD1 | Up to 64L at OD1 |
| Capping agent | Citrate | |||
| Presentation matrix | Suspended in H2O, no preservative | |||
Gold Nanoparticles
Size-matched colloid from 2 nm – 250 nm; ultra-uniform, ≥12-month stability and available in bulk ODs for seamless scale-up.
Control-line Conjugates
Reliable test validity using BSA, chicken IgY, mouse IgG or Protein A 40 nm conjugates - negative or positive controls on demand.
Gold Starter Packs
Unsure which diameter to pick? Evaluation kits supply four key sizes (5-40 nm or 20-80 nm) so you can optimise in a single order.
Tag Conjugates
Ready-made 40 nm labels against biotin, digoxin, FITC, His-tag or HRP—ideal for modular assay designs and multiplex formats.
Anti-human Conjugates
Goat or mouse antibodies to human IgG, IgM, IgA or IgE, adsorbed to 40 nm gold and delivered at OD 10.
Anti-species Conjugates
High-affinity goat antisera to mouse, rabbit or other species on 40 nm gold; build control or detection lines with confidence.
Fertility Conjugates
Monoclonal anti-hCG and anti-LH gold conjugates validated for rapid pregnancy and ovulation tests.
Gold Conjugates
Trusted Gold Conjugates from BBI
All of our conjugates are manufactured using our unique gold nanoparticles. We use our long-established proven processes to manufacture conjugates with outstanding performance and long-term stability. Our catalogue gold conjugates offer optimal performance, cost effectiveness and guaranteed quality, and are designed to help you develop and manufacture your assay rapidly and efficiently.
We manufacture all of our conjugates under our ISO13485 certification at our Crumlin headquarters.
BBI Solutions Gold Conjugates for Microscopy
Gold labels offer an effective method of labelling antigens for visualisation in the electron microscope.
BBI has a range of EM grade conjugates that combine different antibodies on a range of particles, predominantly from 5, 10 and 15nm. For researchers beginning to work with immunogold labelling, we recommend 10nm gold conjugates for observation, at a range of magnifications.
The main advantages of gold labelling lie in the high contrast and unequivocal nature of the label, the range of particle sizes suitable for different magnifications, the extreme sensitivity and the stability of the signal.
Please contact our Customer Services Team directly to discuss your requirements.
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IN FOCUS
ISO Certifications
All our gold colloid and conjugates are manufactured at facilities certified to internationally recognised ISO13485 quality management standards – so your diagnostics start with a proven quality backbone.
Our ISO27001 certification ensures your data is safeguarded, and we’re now charting a path to ISO 14001 and ISO 45001 to fold sustainability and safety into every batch.
ADDING VALUE
Performance
Backed by 70 years of reagent expertise, BBI products are engineered for consistent, assay-grade performance - batch after batch.
Scalability
From pilot-scale to full scale industrial runs, our bioprocesses and global logistics flex with your forecasts, ensuring on-spec supply worldwide.
Compliance
ISO 13485 certification plus FDA registration and full documentation make every lot audit-ready - speeding global approvals and market entry.
Security
Global primary manufacturing and secure supply chains ensure security of supply, so your production timeline stays protected.
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GET IN TOUCH
Still need help? Talk to our team
Our customer service team is on hand to help with any questions you have or support you need.
And if the issue is technical, they’ll bring in our world-leading expert scientists to troubleshoot side-by-side with you and keep your project moving.
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