Gold Conjugates
Gold colloid is commonly used in lateral flow and rapid diagnostic assays due to its strong optical signal, ease of use, and compatibility with passive conjugation. While the underlying chemistry is simple, achieving a conjugate that is stable, sensitive, and consistent requires careful optimisation and an understanding of how proteins interact with nanoparticle surfaces.
With more than 20 years of experience working with nanoparticles, our scientists support assay developers in producing gold conjugates tailored to their application. We conjugate antibodies and proteins using either client supplied material or sourced on request, developing each conjugate to match the intended assay format.
Because gold conjugation relies on surface interactions rather than covalent chemistry, small changes in conditions can significantly affect performance. For this reason, conjugates are developed with close attention to both physical stability and biological function.
Contact us via our enquiry form to discuss your specific gold conjugate needs.
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Why Choose Our Gold Conjugation Service:
+ Nanoparticle expertise - Over 20 years’ experience working with protein - nanoparticle interactions.
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+ Tailored Conjugates - Conjugation conditions optimised for your target, format, and sensitivity.
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+ Minimal material - Initial assessment typically requires only 1–2 mg of antibody / protein​
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+ Comprehensive characterisation - Stability, optical behaviour and functional performance.
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+ Designed for scale and supply - Bench-scale optimisation can be transitioned to bulk production
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Key Factors in Gold Conjugation
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pH and Antibody Loading
Conjugation conditions, including pH and antibody loading, are carefully optimised based on the antibody’s isoelectric point, type, and purity to achieve uniform particle coating, maintain colloid stability, and ensure reproducible, assay ready performance.
Salt Stability
​Gold colloid stability is monitored through salt challenge testing, which assesses surface coverage and particle robustness. Well coated conjugates remain red, while insufficiently stabilised particles aggregate, causing a visible colour shift.
UV–Visible Spectroscopy
​UV–Vis spectroscopy is used to monitor colloid stability, with a sharp ~530 nm peak indicating well dispersed particles and peak broadening or increased absorption at 600–700 nm signaling aggregation, complementing salt stability testing for robust conjugate assessment.
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Functional Performance
Conjugates can be tested for biological activity to ensure antibodies remain functional, using approaches such as anti-species binding or full immunoassay evaluation to confirm assay ready performance.​