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Ultrasound has potential to damage coronaviruses, study finds


Ultrasound has potential to damage coronaviruses, study finds

The coronavirus’ structure is an all-too-familiar image, with its densely packed surface receptors resembling a thorny crown. These spike-like proteins latch onto healthy cells and trigger the invasion of viral RNA. While the virus’ geometry and infection strategy is generally understood, little is known about its physical integrity.
A new study by researchers in MIT’s Department of Mechanical Engineering suggests that coronaviruses may be vulnerable to ultrasound vibrations, within the frequencies used in medical diagnostic imaging.
Through computer simulations, the team has modeled the virus’ mechanical response to vibrations across a range of ultrasound frequencies. They found that vibrations between 25 and 100 megahertz triggered the virus’ shell and spikes to collapse and start to rupture within a fraction of a millisecond. This effect was seen in simulations of the virus in air and in water.
The results are preliminary, and based on limited data regarding the virus’ physical properties. Nevertheless, the researchers say their findings are a first hint at a possible ultrasound-based treatment for coronaviruses, including the novel SARS-CoV-2 virus. How exactly ultrasound could be administered, and how effective it would be in damaging the virus within the complexity of the human body, are among the major questions scientists will have to tackle going forward.
“We’ve proven that under ultrasound excitation the coronavirus shell and spikes will vibrate, and the amplitude of that vibration will be very large, producing strains that could break certain parts of the virus, doing visible damage to the outer shell and possibly invisible damage to the RNA inside,” says Tomasz Wierzbicki, professor of applied mechanics at MIT. “The hope is that our paper will initiate a discussion across various disciplines.”
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.
A spiky shell
As the Covid-19 pandemic took hold around the world, Wierzbicki looked to contribute to the scientific understanding of the virus. His group’s focus is in solid and structural mechanics, and the study of how materials fracture under various stresses and strains. With this perspective, he wondered what could be learned about the virus’ fracture potential.
Wierzbicki’s team set out to simulate the novel coronavirus and its mechanical response to vibrations. They used simple concepts of the mechanics and physics of solids to construct a geometrical 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 spikes.
From previous studies, scientists have mapped out the general structure of the coronavirus — a family of viruses that s HIV, influenza, and the novel SARS-CoV-2 strain. This structure consists of a smooth shell of lipid proteins, and densely packed, spike-like receptors protruding from the shell.
With this geometry in mind, the team modeled the virus as a thin elastic shell covered in about 100 elastic spikes. As the virus’ exact physical properties are uncertain, the researchers simulated the behavior of this simple structure across a range of elasticities for both the shell and the spikes.
“We don’t know the material properties of the spikes because they are so tiny — about 10 nanometers high,” Wierzbicki says. “Even more unknown is what’s inside the virus, which is not empty but filled with RNA, which itself is surrounded by a protein capsid shell. So this modeling requires a lot of assumptions.”
“We feel confident that this elastic model is a good starting point,” Wierzbicki says. “The question is, what are the stresses and strains that will cause the virus to rupture?”

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