Ultrasound can damage coronaviruses, a new MIT study finds. Credit: MIT News, with images from iStockphoto
Simulations show that ultrasound waves at medical image frequencies can cause the virus’ shell and tips to collapse and break.
The structure of the coronavirus is an all too familiar image, with its densely packed surface receptors resembling a thorny crown. These vein-like proteins adhere to healthy cells and cause the penetration of viral RNA. Although the geometry and infection strategy of the virus is generally understood, 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 imaging.
Using computer simulations, the team modeled the mechanical response of the virus to vibrations over a range of ultrasonic frequencies. They found that vibrations between 25 and 100 megahertz cause the virus’ shell and nails to collapse and break within a fraction of a millisecond. This effect has been seen in simulations of the virus in air and water.
The results are preliminary and based on limited data regarding the physical properties of the virus. Nevertheless, the researchers say their findings are a first tip for a possible ultrasound-based treatment for coronaviruses, including the novel EARS-CoV-2 virus. The most important questions that scientists will have to deal with going forward are how ultrasound can be administered and how effectively it can damage the virus within the complexity of the human body.
‘We have proven that the coronavirus shell and nails will vibrate under ultrasonic excitation, and that the amplitude of the vibration will be very large, producing strains that can break certain parts of the virus, causing visible damage to the outer shell can cause and possibly invisible damage. to the RNA, ”says Tomasz Wierzbicki, professor of applied mechanics at MIT. “The hope is that our paper on different disciplines will start a discussion.”
The team’s results appear online in the Journal of the Mechanics and Physics of Solids. Wierzbicki’s co – authors are Wei Li, Yuming Liu and Juner Zhu at MIT.
The 3D image of the crashing virus, on the right, is captured at the moment of maximum vibration amplitude. Spikes have been removed from the color code plot, left, for clarity. Credit: thanks to the researchers
A stinging shell
While the Covid-19 pandemic took hold worldwide, Wierzbicki wanted 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 break under different stresses and strains. With this perspective, he asked himself what can be learned about the breaking potential of the virus.
The Wierzbicki team tried to simulate the new coronavirus and its mechanical response to vibrations. They use simple concepts of the mechanics and physics of solids to construct a geometric and computational model of the virus structure, which they have based on limited information in the scientific literature, such as microscopic images of the virus’ shell and nails.
From previous studies, scientists have mapped the general structure of the coronavirus – a family of viruses containing HIV, flu and the new SARS-CoV-2 strain. This structure consists of a smooth shell of lipid proteins, and tightly packed, vein-like receptors protruding from the shell.
With this geometry in mind, the team modeled the virus as a thin elastic shell covered with about 100 elastic points. Since the exact physical properties of the virus are uncertain, the researchers simulated the behavior of this simple structure over a variety of elasticities for the shell and the nails.
“We do not know the material properties of the nails, because they are so small – about 10 nanometers high,” says Wierzbicki. “Even more unknown is what is inside the virus, which is not empty, but is filled with RNA, which itself is surrounded by a protein capsule shell. This modeling therefore requires many assumptions. ”
“We feel confident that this elastic model is a good starting point,” says Wierzbicki. “The question is, what is the voltage and voltage that causes the virus to break?”
A Corona’s Crash
To answer the question, the researchers introduced acoustic vibrations into the simulations and observed how the vibrations gripped through a virus structure over a range of ultrasound frequencies.
The team started with vibrations of 100 megahertz, or 100 million cycles per second, which they said would be the natural vibrational frequency of the shell, based on the known physical properties of the virus.
When they exposed the virus to 100 MHz ultrasound excitation, the virus’ natural vibrations could not be detected at first. But within a fraction of a millisecond, the external vibrations, which resonate with the frequency of the natural oscillations of the virus, cause the shell and nails to bend inward, similar to a ball fading as it bounces off the ground. .
As the researchers increase the amplitude or intensity of the vibrations, the shell may break – an acoustic phenomenon known as resonance, which also explains how opera singers can crack a wine glass if they sing at the right pitch and volume. At lower frequencies of 25 MHz and 50 MHz, the virus bent and broke even faster, both in simulated air environments and water similar to fluids in the body.
“These frequencies and intensities are within the range safely used for medical imaging,” says Wierzbicki.
To refine and validate their simulations, the team works with microbiologists in Spain, who use atomic force microscopy to observe the effects of ultrasound vibrations on a type of coronavirus that occurs exclusively in pigs. If it can be experimentally proven that ultrasound can damage coronaviruses, including SARS-CoV-2, and if it can be shown that this damage has a therapeutic effect, the team intends that ultrasound, which is already used to break up kidney stones and to release drugs via liposomes can be used to treat and possibly prevent coronavirus infection. The researchers also believe that miniature ultrasound converters, fitted to phones and other portable devices, could potentially protect people from the virus.
Wierzbicki stresses that much more research needs to be done to confirm whether ultrasound may be an effective strategy for treating and preventing coronaviruses. As his team works to improve the existing simulations with new experimental data, he plans to utilize the specific mechanics of the novel and quickly mutate the SARS-CoV-2 virus.
“We looked at the common coronavirus family and are now looking specifically at the morphology and geometry of Covid-19,” says Wierzbicki. “The potential is something that could be huge in the current critical situation.”
Reference: “Effect of receptors on the resonant and transient harmonic vibrations of Coronavirus” by Tomasz Wierzbicki, Wei Li, Yuming Liu and Juner Zhu, 18 February 2021, Journal of the Mechanics and Physics of Solids.
DOI: 10.1016 / j.jmps.2021.104369