APR 23, 2020 12:00 PMBY LOIS YOKSOULIAN  | PHYSICAL SCIENCES EDITOR  | 217-244-2788

CHAMPAIGN, Ill. — Most viral test kits rely on labor- and time-intensive laboratory preparation and analysis techniques; for example, tests for the novel coronavirus can take days to detect the virus from nasal swabs. Now, researchers have demonstrated an inexpensive yet sensitive smartphone-based testing device for viral and bacterial pathogens that takes about 30 minutes to complete. The roughly $50 smartphone accessory could reduce the pressure on testing laboratories during a pandemic such as COVID-19.

The results of the new multi-institutional study, led by University of Illinois at Urbana-Champaign electrical and computer engineeringprofessor Brian Cunningham and bioengineeringprofessor Rashid Bashir, are reported in the journal Lab on a Chip.

“The challenges associated with rapid pathogen testing contribute to a lot of uncertainty regarding which individuals are quarantined and a whole host of other health and economic issues,” Cunningham said.

The study began with the goal of detecting a panel of viral and bacterial pathogens in horses, including those that cause severe respiratory illnesses similar to those presented in COVID-19, the researchers said.

“Horse pathogens can lead to devastating diseases in animal populations, of course, but one reason we work with them has to do with safety. The horse pathogens in our study are harmless to humans,” Cunningham said.

A schematic drawing of the new device system.

Graphic courtesy Brian Cunningham

The new testing device is comprised of a small cartridge containing testing reagents and a port to insert a nasal extract or blood sample, the researchers said. The whole unit clips to a smartphone.

Inside the cartridge, the reagents break open a pathogen’s outer shell to gain access to its RNA. A primer molecule then amplifies the genetic material into many millions of copies in about 10 or 15 minutes, the researchers said. A fluorescent dye stains the copies and glows green when illuminated by blue LED light, which is then detected by the smartphone’s camera.

“This test can be performed rapidly on passengers before getting on a flight, on people going to a theme park or before events like a conference or concert,” Cunningham said.  “Cloud computing via a smartphone application could allow a negative test result to be registered with event organizers or as part of a boarding pass for a flight. Or, a person in quarantine could give themselves daily tests, register the results with a doctor, and then know when it’s safe to come out and rejoin society.”

There are a few preparatory steps currently performed outside of the device, and the team is working on a cartridge that has all of the reagents needed to be a fully integrated system. Other researchers at the U. of I. are using the novel coronavirus genome to create a mobile test for COVID-19, and making an easily manufactured cartridge that Cunningham said would improve testing efforts.

Study co-authors with Cunningham and Bashir were Fu Sun, Anurup Ganguli and Matthew B. Wheeler, of the U. of I.; and Ryan Brisbin and David L. Hirschberg, of RAIN Incubator; Krithika Shanmugam, of the University of Washington; and veterinarian David M. Nash.

The National Science Foundation and the Center for Genomic Diagnostics at the U. of I. ’s Carl R. Woese Institute for Genomic Biology supported this research.

Bashir also is the dean of the Grainger College of Engineering at Illinois.

Cunningham also is affiliated with bioengineering and materials science and engineering, the Carl R. Woese Institute for Genomic Biology, the Holonyak Micro and Nanotechnology Lab, the Carle Illinois College of Medicine and the Beckman Institute for Advanced Science and Technology at Illinois.

Cunningham serves as a consultant to and owns stock in Reliant Immune Diagnostics, the company that licensed the technology described in this news release.

CHAMPAIGN, Ill. — A fast, inexpensive yet sensitive technique to detect cancer markers is bringing researchers closer to a “liquid biopsy – a test using a small sample of blood or serum to detect cancer, rather than the invasive tissue sampling routinely used for diagnosis.

Researchers at the University of Illinois developed a method to capture and count cancer-associated microRNAs, or tiny bits of messenger molecules that are exuded from cells and can be detected in blood or serum, with single-molecule resolution. The team published its results in the Proceedings of the National Academy of Science.

“Cancer cells contain gene mutations that enable them to proliferate out of control and to evade the immune system, and some of those mutations turn up in microRNAs,” said study leader Brian Cunningham, an Illinois professor of electrical and computer engineering. Cunningham also directs the Holonyak Micro and Nanotechnology Lab at Illinois.

“There are specific microRNA molecules whose presence and concentration is known to be related to the presence and aggressiveness of specific types of cancer, so they are known as biomarkers that can be the target molecule for a diagnostic test,” he said.

Cunningham’s group developed a technique named Photonic Resonator Absorption Microscopy to capture and count microRNA biomarkers. In collaboration with professor Manish Kohli at the Moffitt Cancer Center in Florida, they tested PRAM on two microRNAs that are known markers for prostate cancer.

They found it was sensitive enough to detect small amounts that would be present in a patient’s serum, yet also selective enough to detect the marker among a cocktail of molecules that also would be present in serum.

“One of the main challenges of biosensing is to maintain sensitivity and selectivity at the same time,” said Nantao Li, a graduate student and co-first author. “You want it to be sensitive enough to detect very small amounts, but you don’t want it to pick up every RNA in the blood. You want this specific sequence to be your target.”

Each dot seen in this PRAM image represents one microRNA that has bound to the sensor.

Image courtesy of Nantao Li

PRAM achieves both qualities by combining a molecular probe and a photonic crystal sensor. The probe very specifically pairs to a designated microRNA and has a protective cap that comes off when it finds and binds to the target biomarker. The exposed end of the probe can then bind to the sensor, producing a signal visible through a microscope.

Each individual probe that binds sends a separate signal that the researchers can count. This means researchers are able to detect much smaller amounts than traditional methods like fluorescence, which need to exceed a certain threshold to emit a measurable signal. Being able to count each biomarker also carries the added benefit of allowing researchers to monitor changes in the concentration of the biomarker over time.

“With PRAM, we squirt a sample into a solution and get a readout within two hours,” said postdoctoral researcher Taylor Canady, a co-first author of the study. “Other technologies that produce single-molecule readouts require extra processing and additional steps, and they require a day or more of waiting. PRAM seems like something that could be much more feasible clinically. In addition, by using an optical signal instead of fluorescence, we could one day build a miniaturized device that doesn’t need a trained laboratory technician.”

The PRAM approach could be adapted to different microRNAs or other biomarkers, the researchers say, and is compatible with existing microscope platforms.

“This approach makes the idea of performing a ‘liquid biopsy’ for low-concentration cancer-related molecules a step closer to reality,” Cunningham said. “This advance demonstrates that it is possible to have an inexpensive and routine method that is sensitive enough to require only a droplet of blood. The results of the test might tell a physician whether a regimen of chemotherapy is working, whether a person’s cancer is developing a new mutation that would make it resistant to a drug, or whether a person who had been previously treated for cancer might be having a remission.”

The Carl R. Woese Institute for Genomic Biology at the U. of I. and the National Institutes of Health supported this work. Illinois chemistry professor Yi Lu and bioengineering professor Andrew Smith were coauthors of the work.