Sensor promises disease detection with naked eye

Low-cost color-coded sensor out of the U.K. could let doctors in developing countries detect the presence of viruses including HIV at a glance.

British scientists have come up with a super-sensitive prototype sensor that lets doctors detect early stage diseases with the naked eye, an innovation that could prove valuable in countries that lack the resources for expensive diagnostic equipment.

The sensor, created at Imperial College London, relies on nanotechnology to analyze serum derived from blood samples.

Blue indicates positive and red signifies negative in a new visual recognition test. Imperial College London

A positive reaction to p24, a protein that indicates early HIV infection, or PSA, a protein that at certain levels can indicate prostate cancer, generates irregular clumps of nanoparticles that emit a blue color in a solution kept in a disposable container.

A negative reaction, however, causes the nanoparticles to separate into ball-like shapes, creating a reddish hue. The colors are easily distinguishable at a glance.

While simple and quick HIV tests are already used to test saliva , they can only detect the virus when it hits relatively high concentrations. Concentrations of the p24 antigen are high in the first few weeks after infection, meaning an easy-to-administer test that recognizes it could be used for early diagnosis when antibody levels are still low.

Scientists have previously looked for p24 to detect HIV in newborns, Molly Stevens, an Imperial College London professor of biomedical materials and regenerative medicine who headed the research team, told Crave. Newborns with infected mothers can inherit the antibodies but not be infected, a circumstance that can yield a false positive.

The U.K. scientists say their technology is 10 times more sensitive than current methods for measuring biomarkers, and in fact showed viral loads in HIV-infected patients that were undetectable by the popular enzyme-linked immunosorbent assay (ELISA) test, as well as a gold-standard nucleic acid-based test.

"Our approach affords for improved sensitivity, does not require sophisticated instrumentation, and...is 10 times cheaper, which could allow more tests to be performed for better screening of many diseases," Stevens said. The team's research appears in the latest issue of the journal Nature Nanotechnology.

In addition to HIV detection, the test can be employed to spot the presence of prostate-specific antigen at ultralow concentrations, according to Stevens. This is useful for the diagnosis of prostate cancer recurrence after a total prostatectomy. (Once the prostate has been removed, the PSA should be absent; detection of ultralow levels of the antigen therefore suggests the cancer is growing again.)

Stevens said the test could also be modified to test for additional conditions, such as tuberculosis or Leishmaniasis, a disease spread by the bite of the female sandfly.

She and the study's co-author, Roberto de la Rica, now plan to approach nonprofit global health organizations to ask for strategic direction and funding for manufacturing the sensors and distributing them in low-income countries.

The sensor joins an ever-growing roster of recent health diagnostic technologies being developed for low-income countries. These include, among others, the CellScope , a small, portable microscope that attaches to cell phones, and a blood-analysis chip that detects disease in minutes.

For a far more technical description of how the visual sensor works, have a look at this PDF that details the research.

 

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