Paper-Based Test Rapidly Diagnose Viral Diseases in Remote Areas

A paper-based device has been developed that changes color, depending on whether the patient has Ebola, yellow fever or dengue and will facilitate diagnosis in remote, low-resource settings.

Standard approaches for diagnosing viral infections include polymerase chain reactions (PCR) and enzyme-linked immunosorbent assays (ELISA) that detect pathogens directly or indirectly and these require technical expertise and expensive equipment.

Scientists at the Massachusetts Institute of Technology (Cambridge, MA, USA) and their colleagues built silver nanoparticles in a rainbow of colors and the sizes of the nanoparticles determine their colors. The team uses different sizes of these chemical ingredients for various hues. They then attached red, green or orange nanoparticles to antibodies that specifically bind to proteins from the organisms that cause Ebola, dengue or yellow fever, respectively. They introduced the antibody-tagged nanoparticles onto the end of a small strip of paper. In the paper's middle, the researchers affixed capture antibodies to three test lines at different locations, one for each disease.

To test the device, the team spiked blood samples with the viral proteins and then dropped small volumes onto the end of the paper device. If a sample contained dengue proteins, for example, then the dengue antibody, which was attached to a green nanoparticle, latched onto one of those proteins. This complex then migrated through the paper, until reaching the dengue fever test line, where a second dengue-specific antibody captured it. That stopped the complex from going farther down the strip, and the test line turned green. When they tested samples with proteins from Ebola or yellow fever, the antibody complexes migrated to different places on the strip and turned red or orange. The test takes minutes and does not need electricity.

Kimberly Hamad-Schifferli, PhD, a lead scientist in the project, said, “Using other laboratory tests, we know the typical concentrations of yellow fever or dengue virus in patient blood. We know that the paper-based test is sensitive enough to detect concentrations well below that range. It's hard to get that information for Ebola, but we can detect down to tens of ng/mL, that's pretty sensitive and might work with patient samples.” The study was presented at the 250th National Meeting & Exposition of the American Chemical Society (ACS), held August 16–20, 2015, in Boston (MA, USA).

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Massachusetts Institute of Technology