Test paper for Ebola

23 October 2014
Posted by Chris Smith.

Scientists in America have developed a cheap and simple test for the Ebola virus which uses just a piece of paper and gives an answer in under 20 minutes.

Harvard's Jim Collins and his colleagues found that Ebola viruscells in a dish can be engineered to make them undergo a colour change when they come into contact with the genetic material of Ebola.

If these cells are then broken apart and their internal constitutents are impregnated and freeze-dried into paper, all of the chemical machinery of the cell remains intact and stable for long periods at room temperature. To make it active again, you just add water, which can take the form of a sample from a patient.

"We've engineered a chemical sensor so that if the genetic signature of Ebola is present, the machinery impregnated into the paper triggers the production of an enzyme that causes a colour change, signalling a positive," says Collins.

Critically, the colour change is visible to the naked eye, meaning that no special equipment is needed to read the test results, although the researchers have been working on other forms of sensor that produce a quantitative colour change which can be read with a low-cost camera and will indicate how much of something is present. They've used this to produce a glucose test for diabetics.

The technique, published this week in the journal Cell, appears to be very sensitive and specific. "We can pick up traces of Ebola even at a very low level," says Collins, "and discriminate accurately between different strains of the virus."

These paper-based biochemical sensors are also very simple and cheap to make and can be engineered very quickly. According to the Harvard team, it takes us just hours and literally pennies to make them.

The same approach can be used to look for bacterial infections, antibiotic resistance and even to screen for other diseases like cancer. Perhaps what's surprising is that no one has tried to do this previously.

"These things are really stable for long periods of time. One of my team has kept them in his desk drawer for months. I don't know why this hasn't been tried before," remarks Collins.

The bottom line is that low-cost, paper-based tests like this, which don't need special storage, handling or trained personnel to use them, are likely to be in high demand, especially in Third World countries. Although the technology isn't ready to be rolled out clinically yet, "we've nonetheless already had a few phone calls from West Africa," says Collins...

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