Researchers have developed a tablet-sized device that can distinguish between antibodies produced in response to SARS-CoV-2 and four other coronaviruses with 100 per cent accuracy.
The team at Duke University in the US demonstrated that the easy-to-use and energy-independent device can reliably detect multiple COVID-19 antibodies and biomarkers simultaneously.
The researchers are working to see if the point-of-care device can be used to predict the severity of a COVID-19 infection or a person’s immunity against variants of the virus.
The platform called “D4 assay” can detect Ebola infections a day earlier than the gold standard polymerase chain reaction (PCR) test, the researchers have shown in a recently.
The results, published in the journal Science Advances on June 25, show how flexible the technology can be to adapt to other current or future diseases.
“The D4 assay took six years to develop, but when the WHO declared the outbreak a pandemic, we began working to compress all of that work into a few months so we could explore how the test could be used as a public health tool,” said Ashutosh Chilkoti, a professor at Duke.
“Our test is designed to be both adaptable and truly point-of-care, and this is clearly a scenario when a portable, fast and cost-effective diagnostic would be most useful,” Chilkoti said.
The technology employs a polymer brush coating that acts as a sort of non-stick coating to stop everything except the desired biomarkers from attaching to the test slide when wet.
The high effectiveness of this non-stick shield makes the D4 assay incredibly sensitive to even low levels of its targets, according to the researchers.
The approach allows researchers to print different molecular traps on different areas of the slide to catch multiple biomarkers at once, they said.
The current iteration of the platform also features tiny patterned tunnels that use the physics of liquids to draw samples through the channels without needing any electricity.
With just a drop of blood and a biomolecular lubricant, the test runs autonomously in minutes, and can be read with a detector roughly the size of a tablet.
“The detector is battery powered and the test doesn’t require any power at all, so you can throw the whole thing into a backpack and truly test at the point-of-care with minimal resources,” said Jason Liu, a PhD student working in the Chilkoti lab who designed and built the detector.
         The researchers tested the assay’s ability to detect and quantify antibodies produced against three parts of the virus — a subunit of the spike protein, a binding domain within the protein that grabs on to cells, and the nucleocapsid protein that packages the virus’s RNA.
The spike protein helps the virus to enter and infect the human cells.
The test was able to spot the antibodies in all of the 31 patients tested with severe cases of COVID-19 after two weeks, the researchers said.
It also reported zero false-positives in 41 samples taken from healthy people before the pandemic started as well as 18 samples taken from individuals infected with four other widely circulating coronaviruses, they said.
The researchers said that the platform’s proven accuracy and flexibility make it a prime candidate for developing into other types of tests or for use in future outbreaks.
For example, the platform could potentially be able to test whether or not people have immunity to the various strains of SARS-CoV-2 that continue to emerge, they said.
“There are a lot of questions from people about whether or not they’re protected from new variants of COVID-19, and our test could answer some of those,” said Jake Heggestad, a PhD student working in the Chilkoti lab who developed the chip for the test.
“We believe that our platform should be able to distinguish between whether people have antibodies that can neutralise emerging variants of concern or if those antibodies aren’t going to be protective against new variants,” Heggestad added.

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