Rapid paper-strip test for Ebola in sight

Doctors working in remote areas may soon have available a paper-strip test that changes color, depending on whether the patient has Ebola, yellow fever or dengue. The paper-strip test differentiates Ebola, dengue and yellow fever.

The new test is featuring at the national meeting of the American Chemical Society (ACS) that is taking place this week in Boston, MA.

The tool works like a home pregnancy test and should help doctors assess potential disease outbreaks, according to the developers.

Standard approaches for testing viral infections accurately and reliably require technical expertise and expensive equipment such as Polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).

But in developing areas far away from big hospitals and laboratories with such equipment, the immediate concern when fever strikes is to quickly establish whether the outbreak is a serious disease that might need quarantine or a less severe illness like the common flu.

This is the problem that the color-changing paper-strip test, developed by Kimberly Hamad- Schifferli, a professor at Massachusetts Institute of Technology (MIT) in Boston, and colleagues, addresses.

Test works like over-the-counter pregnancy test

Prof. Hamad-Schifferli, who heads a mechanical and biological engineering laboratory that develops nanoscale tools, says the test works like the home pregnancy test you can buy over the counter. She notes, however:

“These are not meant to replace PCR and ELISA because we can’t match their accuracy. But this is a complementary technique for places with no running water or electricity.”

The test comprises three strips of paper and silver nanoparticles that have different colors determined by their size. To detect Ebola, the researchers used red nanoparticles carrying antibodies that bind only to Ebola virus proteins. For dengue, they used green nanoparticles, and for yellow fever, they used orange.

Another antibody “captures” the nanoparticles with the attached virus proteins to fix them in a particular position on the strip, that is different for Ebola, dengue and yellow fever.

Technique ‘should work for any disease’

The team tested the tool using small amounts of blood spiked with proteins from the three different viruses. It showed the correct color in the appropriate location on the paper strip, depending on which virus protein was being tested.

For example, if a sample contained the Ebola proteins, the Ebola antibody and red nanoparticle combination picked them up and traveled through the paper until it encountered the second Ebola “capture” antibody located in the middle of the strip. Once captured, the complex stopped in that location, leaving the red color clearly showing in the middle of the strip.

“The strip looks so simple, but it’s incredibly complicated,” Prof. Hamad-Schifferli says. “Putting it all together in an integrated system was really challenging.”

She says they know their test can detect concentrations of dengue and yellow fever that are well below those found in patients’ blood. They are still working on finding out whether this is true of Ebola, but they suspect it is as the test can detect down to tens of nanograms per milliliter.

The team says the platform should work for any disease – you just use the appropriate antibodies. They are planning to make kits for free distribution, as Prof. Hamad-Schifferli explains:

“We’re giving people the components so they can build the devices themselves. We are trying to move this into the field and put it in the hands of the people who need it.”

Earlier this month, Medical News Today reported a study that found an existing class of drugs may be able to halt Ebola virus and its cousin the Marburg virus. In the Journal of Virology, a team from the University of Illinois at Chicago describes how it screened 1,000 compounds and found 20 GPCR antagonists that were able to stop Ebola and Marburg viruses from entering host cells.

Written by Catharine Paddock PhD

http://www.medicalnewstoday.com/articles/298322.php

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