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MIT Team Develops Multiplexed POC Immunoassay for Infectious Disease Testing

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NEW YORK(GenomeWeb) – Massachusetts Institute of Technology researchers have developed a point-of-care immunoassay platform capable of multiplexed disease detection.

The device was detailed in a study published in the journal Lab Chip and in a presentation this week at the National Meeting & Exposition of the American Chemical Society inBoston. It uses silver nanoparticles functionalized with antibodies to the target infectious agents and requires no electricity, cold storage, specialized reagents, or other infrastructure, making it a potentially ideal platform for field work in resource-constrained environments, said Kimberly Hamad-Schifferli, an MIT researcher and author on the paper.

In an initial demonstration of the technology, Hamad-Schifferli and her colleagues developed a version that tested simultaneously for dengue, yellow fever, and Ebola, finding that it could distinguish between the three infections at limits of detection suitable for clinical work.

The researchers are now in discussions with potential commercial partners about making the platform available. "Obviously as an academic lab we are not doing any manufacturing, so we are looking into options for that," Hamad-Schifferli said.

Additionally, she noted, they have distributed supplies to collaborators in the field to get their feedback on the format and its usefulness.

"We can assemble a device here in Cambridge in air conditioning and a controlled environment with good lighting and we can make it work fine," she said. "But [will it work for] somebody who is on the ground in thePhilippines? Is it feasible? Does it make sense? These are things that we don't really get to find out in the lab, so we're trying to give it to the people who will use it in the end."

The MIT platform is based on a lateral-flow design much like a pregnancy test with the key advance being its multiplexing capabilities, Hamad-Schifferli said.

To achieve multiplexing, the researchers used silver nanoparticles which exhibit different colorimetric properties depending on their shape and size. By using different nanoparticle shapes and sizes, each functionalized with antibodies to a different pathogen of interested, they were able to develop a test that would read out a different color depending on the disease present.

None of the individual technologies used in the device were novel, Hamad-Schifferli noted, but the trick was in combining them.

"It was one of those situations where each of the pieces had been done before but no one had really put them all together," she said, adding that the main technical challenge was use of appropriate surface chemistries both on the flow surface and the nanoparticles to prevent cross-reactivity.

"That is always something you have to work out," she said. "There's always a lot of black magic involved. We have a lot of nanoparticle surface chemistry and techniques that we normally use, and then there is the chemistry for the lateral flow devices and a whole set of chemistries they use. So it was a matter of going through and trying to find the conditions that made it work."

Equally key was obtaining good quality antibodies highly specific to the diseases they were testing. In the case of Ebola this was something of a challenge, Hamad-Schifferli said, noted that these reagents are relatively new and difficult to get a hold of.

Hamad-Schifferli said she and her colleagues envision the platform as being primarily used for initial screening of patients suspected to have a particular disease. While the device is not as sensitive or accurate as established testing methods like PCR or ELISA, the fact that it requires essentially no infrastructure to run makes it potentially useful in settings without access to even basic clinics.

For instance, she said, if during an Ebola outbreak health care workers had quarantined a group of people suspected of having the disease, they could use the MIT test to screen these patients and then reflex those with positive results for testing on a more established, resource-intensive platform.

The device presented in the Lab Chip paper multiplexed tests for three diseases. Hamad-Schifferli said she and her colleagues are now working to up that number to around eight to 10 and have had some success with this effort.

One potential issue of higher multiplexing, however, is price, given that detecting additional diseases requires additional antibodies, which represent the bulk of the platform's cost. The triplex platform the researcher recently present costs around $15 to make, although that would likely go down somewhat were it to be manufactured on a larger scale, she said.

"Cheaper would be better," she noted, but, even so, some devices employed during the recent Ebola outbreak in West Africa cost in the range of $10 to $20, she said. "So we always want to make the price lower, but we feel pretty good about it."

A singleplex platform to test for just one target would reduce antibody costs, and the group is experimenting with such set-ups. However, Hamad-Schifferli noted, "there are some distinct advantages to [multiplexing]."

For instance, while in an epidemic situation healthcare workers might be most concerned with one particular disease, it is beneficial nonetheless to be able to help patients suffering from other infections. A multiplex test could both rule out Ebola while detecting other diseases endemic to the area, allowing for more rapid and efficient treatment of that patient population.

And, in the case of diseases that present very similarly, multiplexing allows researchers to more quickly zero in on what is afflicting a patient. For instance, "it is really hard to tell the difference between dengue and chikungunya and malaria" based on initial symptoms, Hamad-Schifferli said, but "the treatment for each is totally different. So it's much easier if you can have them all together in one test."

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