Scientists have developed an ultra-sensitive sensor for doctors to detect viral infections, such as HIV, as well as cancers in their early stages, with the naked eye.

The researchers, from Imperial College London, reported on their prototype sensor in Nature Nanotechnology.

According to the authors, their sensor is ten times more sensitive at measuring biomarkers than anything available today for current gold standard practice.

The sensors are extremely cheap and easy to use, and will be useful in countries where sophisticated equipment is in short supply.

The prototype’s great advantages are twofold:

  • Price – it costs about one tenth of anything else on the market today.
  • It can detect diseases early on, so that patients can be treated in the early stages.

Cheap saliva tests are already available for detecting HIV infection. However, they can only detect the virus when blood concentrations are high.

A trial was carried out to see how well the sensor could detect p24 in blood samples. P24 is a biomarker which points towards HIV infection.

Professor Molly Stevens, who works at the Department of Materials and Bioengineering, Imperial College London, said:

“It is vital that patients get periodically tested in order to assess the success of retroviral therapies and check for new cases of infection. Unfortunately, the existing gold standard detection methods can be too expensive to be implemented in parts of the world where resources are scarce.

Our approach affords for improved sensitivity, does not require sophisticated instrumentation and it is ten times cheaper, which could allow more tests to be performed for better screening of many diseases.”

They also tested for PSA (Prostate Specific Antigen), a biomarker which is commonly used for helping doctors diagnose prostate cancer.

It is possible to reconfigure the sensor, the scientists say, so that it can be used for detecting other diseases and viruses.

The prototype sensor analyzes serum, derived from blood, which is placed in a disposable container. Serum is a clear fluid derived from blood samples.

If the marker is present in the serum, it alters the course of a chemical reaction. If the samples contain p24, a chemical reaction takes place which makes tiny gold particles clump together irregularly, giving a distinctive blue color to the solution in the container. If PSA or p24 levels are not abnormal, the nanoparticles separate into little balls, creating a reddish color.

In both cases, positive and negative results, the reactions in the container can be seen with the naked eye – all you have to do is look at the color of the liquid.

Even in cases where HIV infected patients had low viral loads of p24, the sensor detected them – this is not possible with existing tests, such as ELISA (Enzyme-linked Immunosorbent Assay), nor with the nucleic acid based test.

Co-author, Dr. Roberto de la Rica, said that their prototype will hopefully be able to detect previously undetectable HIV infections and indicators of cancer. If people can be diagnosed sooner and treated sooner, their prognosis improves considerably. Dr de la Rica said “this could pave the way for more widespread use of HIV testing in poorer parts of the world.”

The team will be looking for funding from not-for-profit global health organizations. Their aim is to enable low income countries to have access to this extremely economical and accurate sensor.

Written by Christian Nordqvist