Two Mass-Market, Paper-based Covid-19 Diagnostics Tests in Development

 

Researchers are developing simpler COVID-19 diagnostic tests for use outside of labs in an effort to make mass testing available, fast and inexpensive.

At Iowa State University, Nigel Ruel, assistant professor of chemical and biological engineering, is developing a “no-touch” paper-based test that detects the presence of SARS-CoV-2 based upon electrical frequencies.

When the test is commercialized, a person could cough or rub a nasal swab onto a card, put the card in an envelope, let it incubate overnight and take it to a test collection center or drop it in the mail. A virus-killing coating on the envelope makes it safe for handlers.

The unopened envelope could be scanned at a clinical or municipal testing site to determine whether results were positive or negative and then incinerated.

“We’re trying to make it so that no one has to touch the samples,” Reuel said.

Through-the-envelope diagnostics are possible because this assay is based upon reading the electrical frequency of the RNA samples.

“A small conductive coil is screen-printed on the paper and resonates at a specific radio frequency. This can be detected externally using our reader,” Reuel told BioSpace. “When the coating on the sensor is partially or completely degraded (due to the presence of the virus and generation of the reporter protein), the resonant frequency shifts dramatically. This shift is irreversible, so the envelope can be dry or held at any temperature in transit.”

Reading the test through the envelope, he continued, requires, “A low-cost scanner unit that draws the envelope through at a constant rate. The reader has a built in antenna to broadcast a sweep of frequencies and determine where the resonant frequency occurs. It will also have a scanner to detect a barcode/QR code that will link back to the user.” 

Currently, Reuel and his team are finalizing individual functions that comprise the test. As Reuel said, “Our system has four separate unit operations:

1: amplify viral RNA,

2: recognize viral RNA and open a toehold switch to the reporter protein template,

3: produce reporter protein (enzyme),

4: degrade coating on the RF sensor, using an enzyme.” 

Toehold switches detect target RNA. Once detected, reporter proteins change the frequency of the sensor’s signal. Their developers, Keith Pardee at the University of Toronto and Alexander Green at Arizona State University, are collaborating with Dr. Reuel to apply the technology to SARS-CoV-2 detection.

Physically, the test is a multi-layered assembly. The top layer of paper holds the biological samples, the middle layer contains a toe-hold switch, and the bottom layer is a printed, coiled, resonate circuit that is scanned for telltale frequencies.

Once a sample is scanned, results can be emailed to individuals immediately. His goal is for each reader to process 5,000 samples per day.

“Later this fall we will connect each function to a single, card-based system,” he said. “Next spring, we will validate the test with synthetic viral templates at different test locations, and move to clinical samples.”

Reuel anticipates approaching the FDA in 2021, “once we have validation data in hand.” From that point, he hopes for commercialization by mid-year.

Another paper-based test, which is further along, is being developed by E25Bio to detect SARS-CoV-2 virus in patients.

“The two E25Bio Direct Antigen Rapid Test (DART) products detect SARS-CoV-2 antigen, which allows identification of infected individuals during the active phase of COVID-19,” E25Bio interim CEO and CSO Bobby Broke Herrera told BioSpace.

“We are developing two products, a 30-minute lab test and a 15-minute test for personal use,” Herrera said. “In either case, a nasopharyngeal or nasal swab is collected, the sample is processed, and results are provided visually on the test itself.

“We have achieved the accuracy required by the FDA,” Herrera pointed out. “Our test does a great job of identifying COVID-19 patients – especially those with higher viral loads, who are known to transmit virus more easily to others.”

E25Bio is in discussions with the FDA and hopes to receive emergency use authorization by September. Meanwhile, it is working with two manufacturers – one in the U.S. and one in the UK – in anticipation of a September launch.

The assay is based upon lateral flow technology, in which paper strips are coated with antibodies that bind to particular viral proteins. For diagnostic testing, those strips are dipped into a solution of gold nanoparticles, patient sample, and a marker protein. If the virus of interest – SARS-CoV-2, in this case – is present, the marker protein attaches to the strip, forming a colored line. Like pregnancy tests, the COVID-19 diagnostic is inexpensive, easy-to- use and has a visual readout. No lab processing is needed.

DART is being positioned as a mass population alternative to PCR tests for SARS-CoV-2 identification. Antigen tests are less sensitive than PCR tests, the company said, but during a pandemic, the frequency and coverage of testing may be more important than analytical sensitivity.

“The E25Bio DART can paired with a mobile phone app to report test results and epidemiological data in real-time to the cloud. Diagnosis during the active phase of infection is important because one is able to then isolate (and thus reduce the risk of) transmitting the virus to others,” Herrera said.