NEW YORK – Researchers from the University of Texas at Austin have created a graphene-based device that they say is able to detect COVID-19 and influenza and differentiate the two diseases in less than a minute.
Relatively new as a material for use in diagnostic testing, graphene is a carbon-based, atomically thin nanomaterial that when fabricated in a specific way has "extraordinary electronic properties and is highly conductive and flexible," making it a useful material to adapt for biosensors, said Dmitry Kireev, a research associate in electrical and computer engineering at the university who helped develop the device. When something with a charge comes close to the surface of graphene, the electrical potential of the material is changed and can be recorded by measuring the current going through a device.
As a result, graphene transistors "make excellent sensors that would be sensitive to literally anything with a charge that comes close to the surface" and can be functionalized to detect a specific biomolecule, he said.
Against that backdrop, Kireev and his colleagues decided to build a sensor sensitive to both COVID-19 and influenza that could quickly differentiate between the two respiratory diseases, using COVID-19 and flu antibodies developed by another research group at UT Austin that are able to bind to multiple variants of each virus to functionalize the graphene material. By chemically treating the graphene with an antibody solution and incubating it, they created a solution that includes a linker with a pairing molecule that attaches to the graphene and another linker that attaches to the antibody.
They then built a four-part sensor that has four separate graphene transistors: one part with a COVID-19-specific antibody, one with an influenza-specific antibody, and two sections for controls. The controls were necessary, Kireev said, because biological samples contain "a big cocktail of biomolecules" that could interfere with the test result.
When the test solution, which includes the sample and reagents, is introduced onto the sensor chip, the virus proteins react with the antibodies that are linked to the graphene material and produce an electrical charge, typically within 10 seconds. That electrical charge is then measured and, based on which channel the change of electric charge occurs in, a result is produced.
The researchers described the development of their device in a MedRxiv preprint published in October and presented their work at last month's American Chemical Society spring meeting. A final manuscript describing their device is currently in revision.
Kireev and his research team tested their device using artificial saliva containing proteins from SARS-CoV-2 and influenza, but they still need to validate it with clinical samples, Kireev said, adding that the device can also be used with nasal swab samples dissolved in water, and eventually with more complex sample types like blood.
While the test is currently being used in a laboratory, Kireev said the researchers envision the device being used in a highly populated point-of-care setting where a quick readout is necessary, such as an office building.
Kireev said the team is interested in commercializing the device, but that would require either partners or a startup to help scale up production. The team is trying to focus mainly on the science and technology and has not extensively pursued commercial translation, though the researchers are interested in doing so, he noted. Although the height of the COVID-19 pandemic is likely behind us, Kireev said COVID-19 seems to be "as seasonal as flu and will hardly pass off completely." The researchers see their device as "a technology and multifunctional tool [that] should be in place [and] ready when another outbreak happens."
Another challenge the researchers would also need to address before commercialization is improving the reproducibility of the device, he said. Although the fabrication technique the researchers use to functionalize the graphene is "rather straightforward," it might be difficult to do on a wider scale and would need time and effort to adapt for broader use, Kireev added.
The traditional way of fabricating graphene is by transferring the material onto a silicon wafer and then taking a variety of additional steps, but those steps can contribute to minor damage of the material and affect the sensitivity of the graphene, thus restraining the possible biosensing applications, Kireev said. The UT Austin team's method, however, relies on prefabricating silicon wafers without graphene and then transferring the graphene directly onto the wafers without any other steps, keeping the sensitivity high.
While still not commonly used for diagnostic tests, graphene is increasingly being leveraged as the basis for biosensors for infectious disease diagnosis, although none have achieved the 10-second turnaround time touted by the UT Austin team. For example, Grip Molecular Technologies is developing a multiplex diagnostic testing platform using graphene biosensors to detect upper respiratory infections, while Cleveland-based IdentifySensors Biologics is working on a graphene-based COVID-19 test. In 2017, a research group at Purdue University utilized graphene biosensors to detect mosquito-borne viruses, and in 2021, a team from the University of Illinois at Chicago published a paper on its graphene-based test for SARS-CoV-2.
The U of Texas researchers' platform was developed for COVID-19 and influenza due to the pandemic, but Kireev said it could be adapted and applied to other diseases, as long as the functionalizing antibodies are changed. However, Kireev said that the researchers' current focus is on COVID-19 and influenza, because expanding the range would still be an engineering challenge. There's nothing to stop the developers from adding more channels to detect a broader range of viruses or pathogens or functionalizing the device with different types of molecules, such as aptamers or enzymes, to detect other diseases, and the team is currently working on using its test to differentiate SARS-CoV-2 variants.