Macrocosm: A cell phone app could diagnose a virus within seconds

Marko Geber

Cellphones. We carry them in our pockets. We depend on them for communication, information, and entertainment. According to the Pew Research Center, 96% of Americans own a cellphone of some kind, and 81% own a smartphone - a cellphone that performs a computer's functions. With over 4 in 5 Americans having a computer's worth of processing power in their pockets, new apps that utilize that power appear daily. A health app to monitor progress on a diet or exercise plan. A stock exchange app that updates in real-time, down to the millisecond. A sleep app that measures a user's sleep cycles to wake them up at the most reasonable time.

And now, an app that could detect a virus using a smartphone's camera and a tiny, bubbling chemical reaction.

Scientists at Harvard Medical School and Massachusetts Institute of Technology have published a study on a new system for rapid and sensitive virus detection. This system utilizes only a small microchip and a smartphone camera, circumventing the existing models of virus detection that require bulky attachments and excess hardware. Through this simple methodology and streamlined design, this technology could be made available on a worldwide scale, aiding countries with overburdened healthcare systems and a deficit of doctors. In the current humanitarian crisis of SARS-COV-2, this technology could prove absolutely vital.

To show how this works, we must look at the simple process that enables this reaction - the bubbling of hydrogen peroxide.

How Hydrogen Peroxide Can Reveal a Virus

Most people know hydrogen peroxide as a household antiseptic. It's a staple of the bathroom cabinet, often used to clean out a scrape or disinfect a piercing. Many preteens can remember their feelings on their earlobes and the strange sound they heard when applied. It bubbles, like a freshly opened can of soda.

This reaction is due to the breaking apart of the hydrogen peroxide as soon as it contacts living cells, like blood, or the exposed cells in a fresh piercing. Living cells contain the enzyme catalase, which, as the name implies, catalyzes a reaction and converts the peroxide into water and oxygen gas. This process effectively kills bacteria by breaking down cell walls (as well as the human body's living cells, which leads physicians to advise against using it to clean out wounds). This process creates a white, fizzling foam, like the carbonation of a beverage. We can hear it and see it quickly; this reaction shows catalase presence, and therefore the existence of living cells.

So it's no wonder that this simple reaction can be modified to show viral cells' presence.

The low-cost microchips used in this reaction are covered in antibodies and platinum nanoparticles. The antibodies serve to trap the virus on the chip's surface, and the platinum particles tag themselves onto the virus. This small tag onto the virus creates a cluster of destination points for a reaction; the uncaptured platinum will slide off of the chip, but the ones remaining denote the presence of a virus. A catalyzer solution containing hydrogen peroxide is then added, and the platinum, reacting like catalase in living cells, creates that signature formation of gas bubbles on the chip. This simple reaction can be seen on the chip itself, the bubbles appearing like patches of white fuzz on its black surface.

This is nothing new in the field of virus detection. What makes it unique is the easy interface of the application used to detect the virus.

Making Detection Simpler

One of the chief reasons that this technology will be more accessible and straightforward is the lack of external plug-ins and hardware, says Dr. Hadi Shafiee, an assistant professor at Harvard and the principal investigator in this project.

"You can take a picture with your smartphone," he says. "And our smartphone app can tell you whether it was positive or negative. No imaging, no complex machines, no cellphone attachments for optical magnification."

The trick is an AI system utilized in the app that can tell whether the result is positive or negative, just based on the presence of those chemical bubbles on the microchip. Smartphone-based imaging has grown so advanced that an AI system can pick out the individual bubbles on a thin strip of surface, which helped move this research forward. The imaging was strong enough to pick out viruses at a level of 250 copies of virus per milliliter at an incredibly confident rate.

Through something as non-invasive as a spit sample or nasal swab, this app can detect hepatitis B virus, HCV, Zika, HIV, and even the novel coronavirus. The limit depends on whether the virus will adhere to a given amount of platinum; if there aren't as many open antibody spots for labeling, the chemical reaction isn't as obvious, and the smartphone camera can't capture it. 

Current results, however, are encouraging. As cameras grow more and more advanced, this test could show smaller and smaller concentrations of a virus, potentially catching it before it multiplies enough through a body to induce life-threatening symptoms.

The team behind this study looks forward to this technology being used out in the field. Shafiee emphasizes the importance of another key aspect of this study: anyone's ability to use it.

"A lay-user can perform the test," he says. "The focus was designing something that's so simple that it doesn't need expensive reagents and expensive processes to work. By pressing one button, you can bring in different technologies all at once to do the process."

When Can I Download It?

The research group does not believe that this can be released immediately. It will depend on the wait time on patent and IP applications and whether a company will want to buy it. The technology may also change as it is later commercialized, though Shafiee hopes that its simplicity remains constant.

Commercialization and funding also depend on a pressing need for virus-detection technology, and as COVID numbers surge, that need rapidly grows on a global scale. This technology could revolutionize how we detect coronavirus in overstaffed areas with limited infrastructure that cannot distribute testing. And by utilizing a smartphone that someone already has, the cost of registering for this test is cut tremendously. A coronavirus test can cost anywhere from $23 to $2315, depending on the lab providing it, for various reasons, but an app only needs to be purchased once. This advancement could create an avenue for those who cannot afford to regularly check themselves for the virus (people who, according to Public Health, may be among the most vulnerable to infection).

"This is something global," says Shafiee. "It has nothing to do with just the United States. It has nothing to do with just us. If a product is designed, this should be used everywhere."