A research team at the University of Illinois, Urbana-Champaign has devised a prototype for a portable COVID-19 test that is fast and easy to use.
To get results quickly, the team needed an alternative to reverse transcription polymerase chain reaction (RT-PCR). This is an RNA multiplication process typically used in tests to detect SARS-CoV-2, the virus that causes COVID-19. In the PCR, a nasal sample from a subject gets sent through a multi-step process that involves several controlled temperature changes. It also requires specialized equipment and trained personnel.
The Illinois researchers chose a simpler process to analyze the specimen, called loop mediated isothermal amplification (LAMP). The sample only needs to be heated to one temperature (65°C). It also provides accurate results even if samples are contaminated.
Then, the team designed a small plastic cartridge with some interior mixing spaces and two slots. The sample gets injected into one while the LAMP chemicals go into the other. The two substances interact with each other once they are injected into the cartridge.
“The cartridges are made using modern, high-speed additive manufacturing,” says Bill King, a mechanical science and engineering professor at the University. “The entire thing can be quickly scaled up to hundreds of thousands of tests. Production scale-up is typically the biggest obstacle for commercial applications of microfluidic cartridges, and we can overcome that obstacle using this new approach. Modern additive manufacturing is elastic and scalable, and it can be ramped up very quickly compared with legacy manufacturing technologies.”
For onsite results, the cartridge slides into a hand-held reader which heats the cartridge to 65°C for about 30 min. A smartphone sits in a cradle and picks up the results. The reader illuminates the liquid compartments with light from blue LEDs, while the phone’s rear-facing camera records a movie of the green fluorescent light generated.
The team checked the portable device with additional clinical samples and found that results matched those of the standard PCR lab procedure.
The researchers are exploring whether the device would work with saliva samples so that no one would have to make it easier to take samples and collecting more patient data as they consider regulatory approvals.