Ultrasound has the potential to damage coronaviruses, a new study from MIT has found. Credit: MIT News, with images from iStockphoto
Simulations show that ultrasound waves at frequencies of medical images can cause the collapse and rupture of virus shells and spikes.
The structure of the coronavirus is a very familiar image, with its densely compacted surface receptors that resemble a thorny crown. These thorn-like proteins attach to healthy cells and trigger virus invasion RNA. Although the virus’s geometry and infection strategy are generally known, little is known about its physical integrity.
A new study by researchers in MITThe Department of Mechanical Engineering suggests that coronaviruses may be vulnerable to ultrasound vibrations, within the frequencies used in medical diagnostic images.
Using computer simulations, the team modeled the virus’s mechanical response to vibrations across a range of ultrasound frequencies. They found that vibrations between 25 and 100 megahertz triggered the virus’s shell and spikes to collapse and start to break off in a fraction of a millisecond. This effect was observed in simulations of the virus in air and water.
The results are preliminary and based on limited data on the physical properties of the virus. However, the researchers say their findings are a first indication of a possible ultrasound-based treatment for coronavirus, including the novel. SARS-CoV-2 virus. How exactly the ultrasound could be administered, and how effective it would be to damage the virus within the complexity of the human body, are among the main questions that scientists will have to face in the future.
“We proved that under ultrasound excitation, the coronavirus shell and peaks will vibrate, and the amplitude of that vibration will be very large, producing strains that can break certain parts of the virus, causing visible damage to the outer shell and possibly invisible damage to the internal RNA ”, Says Tomasz Wierzbicki, professor of applied mechanics at MIT. “The hope is that our article will start a discussion in several disciplines.”
The team’s results appear online at Journal of Solid Mechanics and Physics. Wierzbicki’s coauthors are Wei Li, Yuming Liu and Juner Zhu at MIT.
The 3D image of the collapsing virus, right, captured at the instant of the maximum amplitude of vibration. The peaks have been removed from the color-coded chart on the left for clarity. Credit: Courtesy of the researchers
A pointed shell
As the Covid-19 pandemic spread around the world, Wierzbicki sought to contribute to the scientific understanding of the virus. His group’s focus is on solid and structural mechanics, and the study of how materials fracture under various stresses and strains. With that perspective, he wondered what could be learned about the fracture potential of the virus.
Wierzbicki’s team decided to simulate the new coronavirus and its mechanical response to vibrations. They used simple concepts of mechanics and physics of solids to build a geometric and computational model of the virus structure, which they based on limited information in the scientific literature, such as microscopic images of the virus shell and spines.
From previous studies, scientists have mapped the general structure of the coronavirus – a family of viruses that is HIV, influenza and the new SARS-CoV-2 strain. This structure consists of a smooth shell of lipid proteins and densely compacted, thorn-like receptors, protruding from the shell.
With that geometry in mind, the team modeled the virus as a thin elastic shell covered by about 100 elastic tips. Because the exact physical properties of the virus are uncertain, the researchers simulated the behavior of this simple structure in a range of elasticities for the bark and tips.
“We don’t know the properties of the peak materials because they are very small – about 10 nanometers in height,” says Wierzbicki. “Even more unknown is what is inside the virus, which is not empty, but full of RNA, which in turn is surrounded by a protein capsule. Therefore, this modeling requires many assumptions. “
“We are confident that this elastic model is a good starting point,” says Wierzbicki. “The question is, what are the strains and strains that will cause the virus to break?”
The collapse of a crown
To answer that question, the researchers introduced acoustic vibrations in the simulations and observed how the vibrations rippled through the structure of the virus at a range of ultrasound frequencies.
The team started with vibrations of 100 megahertz, or 100 million cycles per second, which they estimated to be the natural vibration frequency of the shell, based on what is known of the virus’s physical properties.
When they exposed the virus to 100 MHz ultrasound excitations, the virus’s natural vibrations were initially undetectable. But in a fraction of a millisecond, external vibrations, resonating with the frequency of the virus’s natural oscillations, caused the shell and thorns to bend inward, similar to a ball that ripples when it bounces off the ground.
As the researchers increased the amplitude or intensity of the vibrations, the shell could break – an acoustic phenomenon known as resonance, which also explains how opera singers can break a glass of wine if they sing in the right tone and volume. At lower frequencies of 25 MHz and 50 MHz, the virus bent and fractured even faster, both in simulated air and water environments, which is similar in density to body fluids.
“These frequencies and intensities are within the range used safely for medical images,” says Wierzbicki.
To refine and validate their simulations, the team is working with microbiologists in Spain, who are using atomic force microscopy to observe the effects of ultrasound vibrations on a type of coronavirus found exclusively in pigs. If the ultrasound can be experimentally proven to damage coronavirus, including SARS-CoV-2, and if it can be shown that this damage has a therapeutic effect, the team predicts that the ultrasound, which is already used to break kidney stones and release drugs through liposomes, they can be used to treat and possibly prevent coronavirus infection. The researchers also predict that miniature ultrasound transducers, installed on phones and other portable devices, may be able to protect people from the virus.
Wierzbicki emphasizes that there is much more research to be done to confirm whether ultrasound can be an effective treatment and prevention strategy against coronaviruses. While his team works to improve existing simulations with new experimental data, he plans to focus on the novel’s specific mechanics, the rapidly changing SARS-CoV-2 virus.
“We looked at the general coronavirus family and now we are looking specifically at the morphology and geometry of Covid-19,” says Wierzbicki. “The potential is something that can be great in the current critical situation.”
Reference: “Effect of receptors on resonant and transient harmonic vibrations of the Coronavirus” by Tomasz Wierzbicki, Wei Li, Yuming Liu and Juner Zhu, February 18, 2021, Journal of Solid Mechanics and Physics.
DOI: 10.1016 / j.jmps.2021.104369