NSF-funded Smartphone COVID-19 Diagnostic Test Could Put Testing in the Hands of the Public

A smartphone diagnostic test for COVID-19 being developed by a University of Utah researcher holds the potential for quick, accurate testing without the need for individuals to go to a healthcare facility. A prototype may be ready within two to three months.

The personal diagnostic is being developed on the premise that screening people for COVID-19 is the best way to contain its spread, and that gold-standard clinical tests are in short supply.

Basically, people would put a drop of their saliva on a sensor that is about the size of a quarter, plug the sensor into their cellphone’s power jack, and use its processing power to analyze the sample for proteins from the SARS-CoV-2 virus.

University of Utah electrical and computer engineering professor Massood Tabib-Azar said the sensor would include an array of tiny devices inside it, each with single-strand DNA (aptamers) that bind to a specific combination of proteins that are unique to COVID-19. To determine whether any binding occurred, the smartphone/sensor combination would measure the electrical resistance in the aptamers and those bound to the virus.

The platform he is developing to detect SARS-CoV-2 is the same platform he developed to detect the Zika virus.

In developing a smartphone-based Zika virus assay, Tabib-Azar used room-temperature electron tunneling induced by the current versus voltage measurements. That work was published in IEEE Sensors Journal March 30. He found that tunneling allowed him to differentiate between aptamers designed to attach to the capsid proteins on Zika viruses and the aptamer-Zika complexes. That provided enough information to identify the Zika virus without the need for DNA sequencing or additional molecular labels.

Specifically, he wrote, “The current through aptamers and aptamer-Zika complexes all have a threshold voltage just before the exponential increase in the junction current. Below this voltage, the leakage currents are different for the aptamer and aptamer-Zika samples.” Therefore, he concluded, the smartphone assay “…is suitable for detecting viruses that are nanometer-scale biomaterials.”

Electron tunneling has been used for the past 70 years to gain information from thin inorganic insulating materials, but has not been explored extensively with organic and biological materials, with the notable exception of DNA and a few other materials.

For both Zika and SARS-CoV-2 viruses, “By increasing the number of devices and single-strand DNA, we can increase the sensor’s accuracy and reduce the false positives and false negatives,” he said in a statement. The sensor also can be made as a standalone device.

The sensor also is being designed to test for the presence of the virus on surfaces – door handles or desks, for example – by brushing a swab on the surface and then on the sensor. It also holds the potential to detect the presence of COVID-19 in floating microscopic particles in the air in enclosed spaces such as an elevator. (Although the virus is currently considered not airborne, studies are being conducted to determine if minute particles of the virus can hang in floating droplets in the air.)

The sensor is reusable. It can destroy the previous sample on it by producing a small electrical current that could heat up and remove or disintegrate the virus. Tabib-Azar says the entire process would use little battery power from the cellphone.

An alternative approach would have people deposit a saliva sample on a disposable sheet placed atop the sensor like a Sticky Note. This would decrease cross contamination on the sensor and eliminate the need to heat up and destroy the sample afterward.

For public health purposes, the smartphone/sensor device also can be designed to upload the results to a central server that maps out positive results in an area, giving researchers a clearer and more accurate picture of where hotspots are with big outbreaks of the virus.

The portable, reusable COVID-19 smartphone-based diagnostic assay is being developed with a $200,000 National Science Foundation Rapid Response Research (RAPID) grant.

In related work, conducted last year, Tabib-Azar developed a smartphone-based contact-tracking application. “Mobile-based epidemic monitoring is nothing but a logical next step, because only the mobile devices that move with people can keep up with the contacts they make,” he wrote in IEEE Access.

Because magnetic field strength is rich in spatial features, it can work indoors and out without the limitations posed by GPS positions, WiFi fingerprints and Bluetooth peer discovery technologies. “It (also) offers better privacy protection,” because it “does not reveal the identity of the device of the location of the trace generation,” he wrote in the paper. Importantly, magnetic field strength-based tracking only detects contacts within a few meters – the approximate distance recommended by public health officials for infection control.

Since that paper was published, Tabib-Azar has continued to optimize the tracking method with more extensive real-life testing situations and environments to enhance reliability.