Ultrasound can damage the coronavirus

The structure of the coronavirus is a too familiar image with dense surface receptors that resemble a crown of thorns. These spiked proteins latch into healthy cells and cause viral RNA invasion. The shape and infection strategy of the virus is generally understood, but little is known about its physical integrity.

A new study by researchers at MIT’s Department of Mechanical Engineering suggests that the coronavirus may be vulnerable to ultrasonic vibrations within the frequencies used in medical imaging.

Through computer simulation, the team modeled the virus’s mechanical response to vibrations over a range of ultrasonic frequencies. They found that vibrations of 25-100 MHz caused virus shells and spikes that collapsed and began to burst in less than a millisecond. This effect was seen in air and water virus simulations.

The results are tentative and are based on limited data on the physical properties of the virus. Nonetheless, researchers say their findings are the first hint of the potential for ultrasound-based treatment of coronaviruses, including the novel SARS-CoV-2 virus. How accurately ultrasound can be administered and how effective it is in damaging the virus in the complexity of the human body is one of the major issues that scientists need to address in the future.

“Under ultrasonic excitation, the coronavirus shell and spikes vibrate, and the amplitude of the vibrations becomes very large, creating strain that can destroy certain parts of the virus, causing visible damage to the outer shell. “To the RNA inside, which has proven to cause invisible damage in some cases,” says Tomasz Wierzbicki, a professor of applied mechanics at MIT. “I hope our treatise will begin discussions across disciplines.”

Team results are displayed online Journal of the Mechanics and Physics of Solids.. Wierzbicki is co-authored by MIT’s Wei Li, Yuming Liu and Juner Zhu.

Pointed shell

When the Covid-19 pandemic took root around the world, Wierzbicki sought to contribute to the scientific understanding of the virus. His group’s focus is on solids and structural mechanics, and how materials break under various stresses and strains. From this point of view, he wondered what he could learn about the potential for virus destruction.

Wierzbicki’s team has embarked on a simulation of the new coronavirus and its mechanical response to its vibrations. They used simple concepts of solid mechanics and physics to build geometric and computational models of viral structure. It is based on limited information in the scientific literature, such as microscopic images of virus shells and spikes.

From previous studies, scientists have revealed the general structure of the coronavirus — a family of viruses that are HIV, influenza, and the new SARS-CoV-2 strain. This structure consists of a smooth shell of lipid proteins and dense spike-like receptors protruding from the shell.

With this shape in mind, the team modeled the virus as a thin elastic shell covered with about 100 elastic spikes. Since the exact physical properties of the virus are unknown, researchers have simulated the behavior of this simple structure over the elastic range of both shells and spikes.

“The spikes are so small that we don’t know the material properties. The height is about 10 nanometers,” says Wierzbicki. “What’s even more unknown is what’s inside the virus. The virus isn’t empty, but it’s filled with RNA and is itself surrounded by a shell of protein capsids. Therefore, many assumptions are made in this modeling. Is required.”

“I’m sure this elastic model is a good starting point,” says Wierzbicki. “The question is, what is the stress and tension that causes the virus to burst?”

Corona collapse

To answer that question, researchers introduced acoustic vibrations into the simulation and observed how the vibrations propagated the structure of the virus over a range of ultrasonic frequencies.

The team started with 100 MHz, or 100 million cycles per second. This was estimated to be the natural vibration frequency of the shell, based on what is known about the physical properties of the virus.

When they exposed the virus to 100MHz ultrasonic excitation, the natural vibration of the virus was initially undetectable. However, within a fraction of a millisecond, an external vibration that resonated with the frequency of the virus’s natural vibration caused the shell and spikes to buckle inward, like a ball that dents as it bounces off the ground.

If researchers increase the amplitude or intensity of vibrations, the shell can break. This is an acoustic phenomenon known as resonance that describes how an opera singer breaks a wineglass when singing at the right pitch and volume. At lower frequencies of 25MHz and 50MHz, the virus buckled and destroyed even faster in simulated environments of both air and water, which has similar densities to body fluids in the body.

“These frequencies and intensities are within the safe range for medical imaging,” says Wierzbicki.

To improve and validate the simulation, the team is working with a Spanish microbiologist to use an atomic force microscope to observe the effects of ultrasonic vibrations on a type of coronavirus found only in pigs. .. If ultrasound can be ly proven to damage coronaviruses, including SARS-CoV-2, and this damage can be therapeutically effective, the team said that ultrasound had already destroyed kidney stones and liposomes. May be used to treat and in some cases prevent coronavirus infections. Researchers also imagine that small ultrasonic transducers attached to phones and other mobile devices may be able to protect people from viruses.

Wierzbicki emphasizes that much more research should be done to see if ultrasound can be an effective treatment and prevention strategy for the coronavirus. His team will focus on specific mechanisms of the rapidly mutating SARS-CoV-2 virus as they are working to improve existing simulations using new data.

“We are focusing on the general coronavirus family, and now we are particularly focused on the morphology and shape of Covid-19,” says Wierzbicki. “The possibilities are great in the current crisis.”

reference: Wierzbicki T, Li W, Liu Y, Zhu J. Receptor effects on coronavirus resonance and transient harmonic vibrations. J Mech Phys Solids.. 2021; 150: 104369. Doi: 10.1016 / j.jmps.2021.104369

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