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Quick Test for Ebola Virus
When diagnosing a case of Ebola virus infection, time is of the essence. However, existing diagnostic tests take at least a day or two to yield results, preventing health care workers from quickly determining whether a patient needs immediate treatment and isolation.
A new test from the Massachusetts Institute of Technology (MIT) could change that. The device, a simple paper strip similar to a pregnancy test, can rapidly diagnose Ebola as well as other viral hemorrhagic fevers, such as yellow fever and dengue fever.
The new device was described in the journal Lab on a Chip.
Currently, the only way to diagnose Ebola is to send blood samples to a laboratory that can perform advanced techniques, such as polymerase chain reaction (PCR), which can detect genetic material from the Ebola virus. This technique is accurate but time-consuming, and some areas of Africa where Ebola and other fevers are endemic have limited access to this kind of technology.
The new device relies on lateral-flow technology, which is used in pregnancy tests and has recently been exploited for diagnosing strep throat and other bacterial infections. Until now, however, no one has applied a multiplexing approach, using multicolored nanoparticles, to simultaneously screen for multiple pathogens.
Unlike most existing paper diagnostics, which test for only one disease, the new MIT strips are color-coded so that they can be used to distinguish among several diseases. To achieve that, the researchers used triangular nanoparticles made of silver that can take on different colors, depending on their size.
The researchers created red, orange, and green nanoparticles and linked them to antibodies that recognize Ebola, dengue fever, and yellow fever. As a patient’s blood serum flows along the strip, any viral proteins that match the antibodies painted on the stripes will get caught, and those nanoparticles will become visible. This can be seen by the naked eye; for those who are colorblind, a cellphone camera could be used to distinguish the colors.
“When we run a patient sample through the strip, if you see an orange band, you know they have yellow fever; if it shows up as a red band, you know they have Ebola; and if it shows up green, then we know that they have dengue,” said Dr. Kimberly Hamad-Schifferli, a visiting scientist at MIT.
The process takes about 10 minutes, allowing health care workers to rapidly perform triage and determine whether patients should be isolated, helping to prevent the disease from spreading further.
The researchers envision their new device as a complement to existing diagnostic technologies, such as PCR. They hope to obtain FDA approval to begin using the device in areas where the Ebola outbreak is still ongoing. To do that, they are now testing the device in the lab with engineered viral proteins as well as serum samples from infected animals.
This type of device could also be customized to detect other viral hemorrhagic fevers or other infectious diseases by linking the silver nanoparticles to different antibodies, the authors said.
The research was funded by the National Institute of Allergy and Infectious Diseases.
Source: MIT; February 24, 2015.