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 antibody fragments- Fab, Fc, ScFv and limited experience with nanobodies.

The majority of gold conjugates (BA Grade and Custom Conjugates) are presented in a low molarity Borax buffer. EM grade conjugates are presented in a Tris-buffer saline solution containing 30% glycerol.

EM Grade gold conjugates can be frozen for long term storage and thawed for usage as these conjugates contain glycerol in their final buffer.

BA Grade and Custom conjugates cannot be frozen. Freezing of these products will cause the gold nanoparticles to completely and irreversibly aggregate and should be avoided.

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.

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 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.

In BBIs experience, 40nm is the preferred particle size. 40nm provides good signal visibility whilst encountering relatively little steric hindrance.

The gold nanoparticles are well dispersed. The conjugate is tested under the Transmission Electron Microscope (TEM) and a specification that ≥85% particles are singlets with no clusters > 10 is applied (except for BA Grade Protein A conjugates where a specification that ≥90% particles are singlets is
applied).

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.

The expiry date is stated on the label of each batch. In general BA Grade conjugates have a shelf life of 2 years from the point of manufacture when stored at 2-8°C. BA.GAM40 stability studies are ongoing- this is currently not supplied with an expiry date.

No expiry date is applied to EM Grade conjugates. Anecdotally, these have been used 5+ years after the date of manufacture with no loss of functionality.

No expiry date is applied to Custom Conjugates, unless at request of the customer. A cost would apply for the panel of work required to assign an expiry date.

The gold conjugates are manufactured at our ISO 13485:2015 certified facility in Crumlin, South Wales, UK.

Your inputs, following discussion of your application with our team,

▪ Selected detector protein (antibody/protein). Supplied by customer or BBI can source and recharge the customer.
▪ Identify target sensitivity
▪ Identify particle size
▪ Concentration of final conjugate required
▪ Provide 3-5mg of protein for conjugation and QC materials (capture, target antigen). Antigen no
more than Cat II Biohazard level

BBI outputs

▪ Initial 5-10ml of final conjugate – (enough for 1000 prototype lateral flow strips*)*using a 1:5
dilution of OD10 conjugate per strip
▪ Excess reagents banked for future production
▪ Full laboratory report on performance customised to your requirements
▪ Access to technical team post conjugation