NEW YORK (360Dx) – A single-cell capture device under development at the Massachusetts Institute of Technology and National Chiao Tung University may lead to a point-of-care diagnostic test for infectious diseases or cancers that costs less than $5 and produces results in less than 10 minutes.
A proof-of-concept prototype of the test relies on oxide functional groups from graphene oxide along with a novel configuration to capture and measure cells from whole blood.
The combination of material and structure is important for a couple of reasons. For one, it makes it possible to build an inexpensive device almost anywhere, Neelkanth Bardhan, an MIT postdoc materials scientist, and one of the lead test developers, said in an interview. You don't need special equipment, and the structure may be easily scaled up to achieve high manufacturing volumes, he added.
These attributes are possible because the test design eliminates the need to fabricate complicated microfluidic channels and avoids the use of expensive lithographic equipment and processes employed by other, similar microfluidic diagnostic tests being developed for the point of care.
“The diagnostic tests we ran in our lab were designed to measure leukocytes, or white blood cells," Bardhan said, adding that the device may as a result be useful in testing for several diseases where you might have an elevated or decreased white blood cell count.
One important application may be to identify bacterial infection at the point of care, and this can be particularly useful in remote locations where sending samples to central or hospital laboratories and waiting more than a week for a test result could negatively hamper patient care. The device may also provide essential on-the-spot diagnostics for wounded soldiers in the field, he said, when a doctor needs to decide whether the optimum treatment is to administer an antibiotic or something else entirely.
"Other disease areas include cancers such as [acute lymphoblastic leukemia] which may be indicated by an elevated white blood cell count, as well as conditions that occur because of the depletion of specific classes of white blood cells,” he noted. One such class, neutrophils, provide the body with its primary defense against certain types of infections.
The current proof-of-concept device is highly specific to capturing one type of cell that presents itself in whole blood. But the developers are starting work on a multiplexed version of the test that will capture many different populations of these cells.
“White blood cells have different subtypes and identifying more of them or fewer of them above or below certain levels can reveal a different medical condition tied to each subtype,” he said, adding that as a next step the team is looking to develop a diagnostic test that employs this approach.
Development may take about a year, but when the test is working, the team hopes to commercialize it, he added. Companies would license the technology and test through a commercial agreement with the MIT technology licensing office, as MIT holds the patent.
In terms of manufacturing, a simple annealing step that occurs at 50° to 80° C without vacuum is one of the most important aspects of the test, Bardhan said.
Adding vacuum, high temperatures, and lithographic fabrication techniques — common in manufacturing of microfluidic chip diagnostic devices — would contribute to greater cost per test and make it more difficult to manufacture, Bardhan added.
Bhardan, born in India, said he is particularly passionate about keeping the cost of the device down so it is possible to manufacture and use it in developing countries. "The deeper into the country you go, the less likely you are to have access to specialty labs," to do testing, he said, and the more reliant you are on point-of-care tests.
"Our method relies on an elegantly simple device, formed by two glass slides — one of which is coated with a nanobody — that are mounted perpendicular to each other with double sided tape," Bardhan said.
That creates the cell capture chamber that holds a volume of 30 µL of blood, and an assembly such as that can be built almost anywhere, he added.
The materials scientists engineer the basic nanostructure of the nanomaterial on a fundamental level to achieve functionalization.
When the oxygen functional groups have been redistributed, the developers functionalize them with a polyethylene glycol linker that attaches onto a nanobody, a single domain subunit of a conventional antibody that is then used to capture specific cells from whole blood.
For proof-of-concept testing, described in January in the journal ACS Nano, the team demonstrated that its thermally-annealed graphene oxide surfaces were almost twice as effective at capturing such cells from whole blood as devices fabricated using untreated graphene oxide, Bardhan said.
The team used graphene oxide because of its properties and its manufacturability. "The material is one atomic layer thick, and spreads out like a sheet of paper," Bardhan said. "What you have is a very large area, but not much in volume. We thought that this kind of thing is beautiful if you want to go ahead and capture certain molecules and use that for diagnostic testing."
The scientific community took note in 2004 upon the discovery of graphene by Andre Geim and Konstantin Novoselov at the University of Manchester. Graphene promised an inexpensive source of carbon with an electron mobility thousands of times greater than silicon, which is used ubiquitously in conventional electronics. It looked like the material had potential for a broad base of uses.
It turned out, however, that graphene by itself, even though it is a perfect conductor, is very difficult to manufacture on a large scale even in the lab setting, Bardhan said. Graphene oxide, on the other hand, has been broadly exploited for research and development work "because the material has a lot of oxide functional groups and you can do a lot with them," Bardhan added.
The work of Bardhan and his team was supported by the Army Research Office Institute for Collaborative Biotechnologies and MIT’s Tata Center for Technology and Design and Solar Frontiers Center.