From bovine disease to COVID-19: Rapid test builds on work with cows
A couple of years ago, I was sitting next to an engineer-farmer who raises beef cattle. He mentioned the challenge of bovine respiratory disease, and how it is difficult to determine what therapy is appropriate because there is a lack of information on which pathogen is causing the disease. Oftentimes, antibiotics fail, and the treatment proceeds by trial and error.
That discussion spearheaded my Purdue lab’s use of biosensors to diagnose bovine respiratory disease. Biosensors are devices like glucose monitors and pregnancy tests that take in a biological molecule and produce a response that can be interpreted. I started working with a few colleagues on campus and my students to use molecular assays (tests) that detect deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and present the result via a simple change in color. Depending on the DNA/RNA sequence, we could distinguish among different types of bacteria and viruses, and potentially among antibiotic-resistant bacteria.
Because the molecular assay works by detecting nucleic acids — essential molecules found in all forms of life — we only had to change the sequence we targeted to apply it to COVID-19. While we were developing the assay for SARS-CoV-2, we learned that saliva serves as an acceptable alternative to a nasopharyngeal swab — that long, cotton-tipped implement that is inserted into the nostril until it feels like it’s tickling the brain — with its costly challenges around transport and reagents, time to result, the PPE supply chain, and the need for expert personnel. We started optimizing our assay to work in saliva so people could collect their own samples and run the test at the point-of-care or potentially at home.
Our innovation is to conduct these molecular assays on paper so that they are easier to use: A person simply adds the sample and doesn’t need to handle multiple reagents. Paper-based devices enable detection of multiple targets on the same device, as well as mass production using roll-to-roll facilities. Since our biosensor detects nucleic acids in saliva, it can also be used for ailments like influenza, and applied to other infectious diseases with some optimization for the matrix (environment) of interest, such as blood or urine.
One of the interesting things about agriculture is that it has a lot of the same issues that are faced in healthcare, but testing is simpler because large numbers of samples from plants and animals are available. Once something is validated through large-sample testing, it is easier, quicker and less costly to repurpose it for other sectors, such as health care.
So far, we have shown that our test can detect the virus in saliva and produce a change from red to yellow on paper in the lab. We are working on optimizing the degree of color change, the versatility of the test, and the processing speed (to provide results within 45 minutes). Meanwhile, we have engaged with industry partners to manufacture test kits at scale. Once the tests are validated clinically, we will apply for FDA emergency use authorization.
With our test, the ideal outcome would be that everyone has a biosensor in their hand and could test themselves every day or every week. If they test positive for COVID-19, they would immediately self-quarantine and avoid spreading the virus.
These biosensors align with the goals of personalized health care, in which professionals collect more timely data on an individual to manage the person’s health more effectively. If we do not develop such biosensors, we will continue to fly blind and lag behind on our interventions until it’s too late. When another infectious disease breaks out, we need to be prepared.
Mohit Verma, PhD
Department of Agricultural and Biological Engineering and Weldon School of Biomedical Engineering
Birck Nanotechnology Center
Colleges of Engineering and Agriculture, Purdue University