What Sounds Do Viruses Make? We Can’t Hear Them, But We Can Make Use Of Them

In a new paper, a multidisciplinary team comprising experts in materials science, optics, acoustics, and virology worked together to develop a way of detecting acoustic vibrations in a single virus particle using light. While the research is still in its early stages, the possibilities it raises are vast.

The key to the method, as corresponding author Dr Elad Harel of Michigan State University told IFLScience, is that it allows for the study of a virus particle in its natural environment. 

You’ve heard of a needle in a haystack problem? This is a needle in a stack of needles, or a needle in a warehouse of needles problem!

Dr Elad Harel

“If we could see these [acoustic] signatures and they were unique, then we could really open up a whole new way of doing biology on microorganisms,” Harel said. “You can immediately see what’s happening […] in real-time. You don’t have to develop assays and do all these very extensive studies. You could do it really, really quickly.”

The problem of labeling

One of the mainstays of biological research is labeling. At a fundamental level, a lot of cells and tissues look pretty similar. To separate out the different cell types in an organ, for example, or to identify healthy tissue from diseased tissue, we rely on adding labels. By tagging specific structures or molecules, often with proteins that glow in different colors or have some other unique property we can measure, we can start to get a picture of the composition of a biological sample. 

But while lots of sophisticated labeling methods have been developed over the years, they’re not without their disadvantages, particularly when it comes to viruses.

“Labeling is very complicated. It’s virus-specific. You’d have to do it for every single new […] virus mutation, [so it’s] very time-intensive, labor-intensive, expensive and so on,” Harel explained. 

Harel’s previous research on nanoparticles – not so very different from viruses, really – inspired the idea of applying some of their methods to biological particles, but there were some bumps in the road at first. 

“We had been measuring these acoustic vibrations in nanoparticles, [and] a virus is a little like a nanoparticle […] – and does it also exhibit these kinds of vibrations? [We] set out to measure that. And we failed many times,” Harel said. “You’ve heard of a needle in a haystack problem? This is a needle in a stack of needles, or a needle in a warehouse of needles problem!”

“We’re detecting photons at the end of the day, and they all look the same. What is it about the photon coming off a virus that looks different from a photon coming off bacteria or coming off a cell fragment?”

But eventually, they cracked it. By effectively “hitting [the virus] with a hammer” as Harel put it, they can induce it to “vibrate in a very specific way that’s sensitive to its structure and properties.” Our natural next question was, “What does it sound like?” but sadly: “it’s almost a million times higher frequency than what humans experience.”

We were really surprised at just how rich these spectra are.

Dr Elad Harel

So instead of listening, Harel and the team use specialized instruments to isolate and pick up scattering of light caused by the miniscule vibrations. They call it BioSonics spectroscopy.

Light and sound

“People have been looking at biology using light for 100 years, but what’s interesting here is that these vibrations of the virus are really distinct from all the other vibrations that are present,” Harel explained to IFLScience. “We were really surprised at just how rich these spectra are, how rich these acoustic signatures are, which means that we can not only sense what the virus is, but we can see what the virus is interacting with. It’s kind of like the virus itself is a sensor of its own environment.”

In practical terms, what that could mean is an ability to watch what a single virus particle is doing in real-time. There are a lot of mysteries still to be solved around virus behavior – a big one is that we still don’t know precisely how virus particles assemble themselves. Harel told us that this method could allow us to visualize that, and if we can see, then we might be able to disrupt it with a new generation of antiviral drugs.

BioSonics could also pave the way for noninvasive sensors that can detect viruses at a distance. “That light is so amazing, right? Because you can get it into places [and] you can get it out without making physical contact,” Harel said. 

“You could do it at a food safety plant if you want to, or you could do it at an airport. […] You shine this laser light and you pick something [up] from 10 meters [33 feet] away.”

Instead of developing highly specific sensors for each virus – or each new variant – this method naturally distinguishes between all different types of viruses. And beyond that, it could also work for bacteria, fungi, and human and animal cells, based on their mechanical differences.

“If you have a steel ball and a rubber ball, they’re going to behave very differently. They’re going to sound quite different when you drop them. That’s kind of the same thing here. […] For example, cancer cells have very different mechanical properties than healthy cells.”

The reason the team started with viruses was because of the huge interest around them right now, but the range of the technique extends six orders of magnitude, expanding its potential applications to a whole lot of biological and chemical systems. They foresee that BioSonics will complement, rather than replace existing techniques like labeling.

They were even able to watch a single virus particle rupturing in real-time. The potential medical implications of being able to tell the difference between functioning and expired virus particles are huge, in terms of detecting active infections.

“This is really early on, granted,” Harel said. “But there’s lots of potential in terms of both the fundamental science, like the drug discovery side, but also the diagnostic, medical application side as well. And so that’s what got us really excited about it.”

The study is published in the journal PNAS.