Improving the Limit of Detection of an infectious disease rapid antigen test: Latex beads vs K-One coated gold nanoparticles

Products & Applications

Kimialys develops custom bioconjugates for Lateral Flow Assay (LFA), leveraging its patented surface chemistry, K-One. K-One optimises the immobilisation of ligands (such as antibody, antigen or protein) on the nanoparticle surface, while fully protecting the remaining surface against non-specific interactions.

With this double benefit, Kimialys’ K-One coating allows LFA developers to reach their target Limit of Detection (LoD), while maintaining the reliability of their assays, but without requiring any further adjustments to the assay manufacturing parameters.

This application note provides a case study of Kimialys’ technology integrated into a rapid diagnostic test targeting an infectious disease protein marker.

Proof of Concept

The performance of a rapid antigen test in dipstick format (no sample pads or conjugate pads) was compared as a function of the bioconjugates used: latex beads versus Kimialys’ gold nanoparticles, with all other components remaining the same (strip, absorption pad, migration buffer, target antigen, capture antibody).

The latex bioconjugates were optimised by a third party through passive adsorption of the capture antibody, while Kimialys’ gold bioconjugates relied on K-One covalent chemistry. The size of the latex beads was not
known, while Kimialys’ gold nanoparticles had a diameter of 40nm ± 3nm.

All experiments were carried out in the provided migration buffer.

Latex Bioconjugates

Image 6

Kimialys’ Bioconjugates

Image 7
Image 9


This short study in dipstick format highlights the three main advantages of Kimialys’ K-One surface chemistry applied to LFA:

Gain in sensitivity: K-One-coated gold nanoparticles generate an 8-fold gain in LoD compared to latex beads. This results from the optimal orientation of the capture antibodies pointing the recognition site (paratope) towards the solution, thereby maximizing capture efficiency.

Background noise removal: No background noise is observed on the strip after the migration of K-One-based bioconjugates, while latex bead migration leads to a faint pink staining. This showcases the optimal protection of the surface brought by K-One against non-specific interactions.

No R&D transfer cost: Switching from latex beads to K-One gold bio-conjugates does not require any change to the other test parameters (membrane, pads, buffers).