Gold Conjugates
Gold Conjugates Built For Manufacture
Over three decades of manufacturing expertise means BBI produce high-quality, reproducible and scalable conjugates that are trusted by our partners worldwide.
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
Control-line Conjugates
Reliable test validity using BSA, chicken IgY, mouse IgG or Protein A 40 nm conjugates – negative or positive controls on demand.
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.
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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 Conjugates
Can the conjugates be frozen?
EM Grade gold conjugates can be frozen for long-term storage as these conjugates contain glycerol in their final buffer. Multiple freeze/ thaw cycles should be avoided.
BA Grade and Custom conjugates cannot be frozen. Freezing of these products will cause the gold nanoparticles to irreversibly aggregate and should be avoided.
What is the optimal size gold nanoparticle for a conjugate for use in lateral flow?
In BBIs experience, 40nm is a good starting point for lateral flow development as it provides good signal visibility whilst encountering relatively little steric hindrance.
60nm and 80nm particles have been shown to give enhanced signals and limit of detection. This can, however, be test-specific.
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.
What pack sizes are available?
EM Grade conjugates are available in 0.25ml and 1ml pack sizes.
BA Grade conjugates are available in 5ml, 100ml and 500ml pack sizes. 5ml will be for samples only.
Custom conjugates are available in any pack size. Minimum order volume is usually 5ml. For orders >500ml, individual pack sizes do not exceed 500ml.
Where are the gold conjugates manufactured?
The gold conjugates are manufactured at our ISO13485:2016 certified facility in Crumlin, South Wales, UK.
How much antibody/protein is needed for a custom conjugation?
For a custom conjugation to a 40nm particle, BBI request 3mg antibody/protein. Minimum concentration 1.0mg/mL. This allows for a full assessment of conjugation parameters prior to committing material to a batch.
Antibody quantity will be slightly more for smaller particle sizes and for alternative detectors (e.g. antigens).
What information is needed to proceed with a custom conjugation?
Antibody pI– this helps with the assessment of conjugation parameters
Antibody source- Monoclonal/Polyclonal/Human/Recombinant. This will determine how we assess the antibody pre-conjugation.
Antibody subtype- this helps with assessment of conjugation parameters
Antibody buffer- no thimerosal in antibody buffer- this can affect binding
Antibody Supplier- considerations around robust long-term supply, availability of multiple lots
Assay format- Sandwich/Competitive/Inhibition/Serological/Non Lateral Flow- different assay formats require different considerations around conjugation parameters.
What QC release tests are used for custom conjugations?
All testing is performed in liquid format.
OD at 520nm- measure of concentration
Dipstick Testing- either anti-species or specific functional system if provided. Determines performance compared to approved past batches.
Free Antibody Check- identify if free antibody is in the solution that could interfere with the assay.
Mono Dispersity Index (MDI)- for 40nm conjugates. A spectral reading as an indicator of potential conjugate stability.
Cluster Check – for conjugate sizes other than 40nm- indicator of potential conjugate stability. A visual count of particles under a Transmission Electron Microscope to check for clustering of particles that may impact stability, performance, and reproducibility.
What materials are needed for QC Testing a custom conjugate?
It is always best to perform in-process assessment and final QC testing with specific functional materials. This is not always possible if material stocks are low or costs high.
BBI requests 0.5mg capture at minimum concentration of 1.0mg/mL.
BBI request approx. 0.1-0.2mg antigen/analyte at 0.1mg/ml (minimum concentration), along with SDS or details of hazards and disposal.
No materials above Biohazard Level II are permitted.
Can BBI perform stability studies on custom conjugates?
BBI can perform stability studies on liquid conjugates at customer request. Please contact us for a quote.
Stability in customer’s final assay will be their own responsibility.
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 happens after the first custom conjugation?
ollowing assessment of conjugate batches in the intended final format by the customer, further optimisation of parameters and conjugate formulation may be required. Prior to validation in customer final application, BBI recommend multiple antibody/ protein lots be conjugated and assessed to ensure robustness in manufacture.
BBI encourages feedback from conjugation events to determine improvements to conjugate formulation to achieve desired performance. This can take the format of emails, presentations or technical calls.
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 Solutions. 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 manufactured on a custom basis at the request of a customer. Antibody conjugation and particle size are chosen by the customer and are optimised for performance in the customer’s test.
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.
What buffer is the gold conjugate presented in?
The majority of gold conjugates (BA Grade and Custom Conjugates) are presented in a low molarity disodium tetraborate buffer.
EM grade conjugates are presented in a Tris-buffer saline solution containing 30% glycerol.
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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.
BBI particles are proven stable for at 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.
Our batch sizes go up to 340l (40nm) to ensure you have a continuous supply.
BBI gold must pass strict quality procedures before it's released to our customers, guaranteeing impressive performance characteristics at scale.
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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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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