Composite material adorned with gold nanoparticles improves infectious disease testing

Researchers at Tohoku University are harnessing the power of composite polymer particles adorned with gold nanoparticles to deliver more accurate means of testing for infectious diseases.

In a paper published in the journal Langmuir, the scientists explain that most testing done today involves antigen-antibody reactions. Fluorescence, absorptions, or colour particle probes are attached to antibodies. When the antibodies stick to a virus such as SARS-CoV-2, these probes visualize the virus’s presence. In particular, the use of colour nanoparticles is renowned for its excellent visuality, along with its simplicity to implement, with little scientific equipment needed to perform lateral flow tests.

Gold colour nanoparticles (AU-NP), with their high chemical stability and unique plasmon absorption, are widely employed as probes in immunoassay tests. According to the researchers, such materials exhibit extreme versatility, with their colours fluctuating based on their size and shape. Additionally, their surface can be modified by using thiol compounds.

Conventional tests that use AU-NP often have to amplify AU-NP’s optical density, so that clinicians can easily measure the strength of the signal produced by the interaction between antibodies and the target substance.

Adding more gold nanoparticles is one means to do this. However, because nanoparticles are tiny, it requires a large quantity of them to achieve a strong enough signal for accurate detection.

To overcome this, the Tohoku researchers proposed a new method called self-organized precipitation (SORP).

SORP works by dissolving polymers into organic solvents before adding a liquid that doesn’t dissolve the polymers well, like water. After the original organic solvent is removed by evaporation, polymers assemble forming tiny particles.

“Using gold nanoparticle decorated polymers (GDNP) assembled by SORP, we set out to see how effective they would be in detecting the influenza virus, and whether they offered improved sensitivity in detecting antigen-antibody reactions,” Hiroshi Yabu, co-author of the paper, said in a media statement. “And it did. Our method resulted in a higher optical density than original AU-NPs and GNDPs decorated with smaller AU-NPs.”

In Yabu’s view, these findings reinforce that GNDP particles have broad utility, extending beyond laboratory settings to real-world diagnostic scenarios.