Rapid paper-strip test for Ebola in sight

19 Aug

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.
Image credit: Chunwan Yen

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,


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


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


“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


The following video from the American Chemical Society describes how the paper-strip test

works and its potential for use as a provisional diagnostic that helps doctors in the field see

how outbreaks are progressing. A paper on the work was also published earlier this year in the journal Lab on a Chip.

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

Copyright: Medical News Today

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