Seeing is believing: Biomarkers visible to the naked eye

Researchers at Imperial College London have created a prototype ultra-sensitive visual test based on gold nanoparticles that can make detecting disease and infection biomarkers possible at a glance. According to the team, the technology is also ten-fold more sensitive than existing "gold standard" techniques, and can be used for a range of biomarkers.

The test is based on the color-changing properties of gold nanoparticles. When the particles, in a disposable container, come in contact with a specific biomarker in blood plasma, they clump together and the solution turns blue. If no markers are present they remain apart and the solution stays a reddish color.

To demonstrate the concept, in research published in Nature Nanotechnology, the team used the nanoparticles to detect a protein called p24, a marker that indicates HIV infection, or prostate specific antigen (PSA), used in the diagnosis of prostate cancer. The setup was able to detect both markers at ultralow levels, picking up p24 in HIV-infected patients who had viral loads undetectable by a gold standard nucleic acid-based test.

Because the results are a simple visual yes/no, Imperial College London's sensor could be used as a low-cost test in countries where sophisticated detection equipment--and the people trained to use it--is scarce or unaffordable. Because it can operate at much lower levels than existing technology, it could support diagnosis at an earlier stage when disease is more easily controlled, or even curable.

Molly Stevens of Imperial College London explained to BBC News: "This method should be used when the presence of a target molecule at ultra-low concentration could improve the diagnosis of disease. For example, it is important to detect some molecules at ultra-low concentrations to test cancer recurrence after tumor removal.

The team plans to approach not-for-profit global health organizations to support manufacturing and distribution of the sensor to low income countries.

- read the abstract
- see the press release
- check out the article in BBC News