Peter Lillehoj, a mechanical engineer from the Rice research team, explained that the goal was “to create a fast, portable device that does not need to be taken to the lab.” They also wanted the device to be able to identify the early phase of infection, “because that is when you want to quarantine and minimize your exposure to other people,” the researcher added.
The tool was therefore designed to detect the SARS-CoV-2 nucleocapsid protein, a biomarker of Covid-19 which can be detected at a very early stage. Lillehoj said:
“We can actually detect very low levels of the protein, down to about 10 picograms per milliliter, which may be about one hundred times lower than most rapid tests. Furthermore, by providing a quantitative result, the test doesn’t just tell you if it is positive or negative, it tells you what the concentration is. The fact that it is a blood test makes it more sensitive.”
Blood provides a real-time overview of the body’s immune response and is less prone to error than a PCR-based swab test. Furthermore, as the test does not involve intermediate steps, it is also less prone to risks or errors in the collection and exchange of samples. As for ease of use, the ultimate goal is that the system not be limited to medical staff and can be used by anyone with appropriate training.
To speed up the sensing process, the Rice research team opted for a unique approach: magnetic nanobeads. Lillehoj explained:
“We coat these beads with two different materials, the antibody and an enzyme. The antibody will allow these beads to attach to that nuclear capsid protein.”
A capillary tube is used to deliver the blood sample to a microchip.
“We then place this microchip on a magnet, it attracts the magnetic beads with the nuclear capsid protein toward the surface of the electrochemical sensor, where the virus material—the protein—is detected.”
The beads then generate a current proportional to the concentration of the biomarker in the sample, that sends a signal to the phone app. If there are no Covid-19 biomarkers, the beads do not bind to the sensor and get washed away in a waste reservoir inside the chip.
While most rapid tests detect the spike protein, because this one is designed to identify the nuclear capsid protein inside the virus, it should also make it easier to detect variants of the virus. Lillehoj said:
“We’re hoping that this will make the test a little more universal for other strains as well. If researchers find that a new strain contains a different protein, we can modify our tests pretty easily to test for a different protein.”
The test is still in the research and development stage, but with the U.S. FDA‘s fast-track emergency use approval, the process could be completed within a year, according to Lillehoj.