The structure of the coronavirus is a very familiar image, with the surface receptors full of folds resembling a crown of thorns. These spike-like proteins give birth to healthy cells and attack viral RNA. Although the geometry strategy and infectivity of the virus are generally understood, little is known about 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 mechanical response of the virus to vibration over a range of ultrasound frequencies. They found that vibrations between 25 and 100 megahertz caused the virus’ shell and spikes to fall off and begin to break within a fraction of a million million. 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. Nevertheless, the researchers say their findings are the first idea of ultrasound-based treatment for coronaviruses, including the novel SARS-CoV-2 virus. Just how ultrasound could be administered, and how effective it would be in damaging the virus within the complexities of the human body, are among the major questions that will be addressed. scientists have to deal with them going forward.
“We have shown, under ultrasound excitation, that the coronavirus shell and spikes are activated, and that the magnitude of that vibration is very large, emitting rays that can break down certain parts of the virus. , causing visible damage to the outer shell and possibly invisible damage to the inner RNA, ”says Tomasz Wierzbicki, professor of applied mechanics at MIT. “Hopefully our paper will start a debate on a number of topics.”
The team ‘s results appear online in the Journal of Solids Mechanics and Physics. Co-authors Wierzbicki are Wei Li, Yuming Liu, and Juner Zhu at MIT.
Spike shell
As the Covid-19 pandemic spread worldwide, Wierzbicki was looking to contribute to a scientific understanding of the virus. His organization’s focus is on rigid and structural mechanics, and a study of how materials break under different pressures and layers. With this view, he wondered what could be learned about the ability to break down the virus.
Wierzbicki’s team attempted to simulate the novel coronavirus and its mechanical response to vibration. They used simple concepts of solid state mechanics and physics to construct a geometric and computational model of the structure of the virus, which were based on limited information in the scientific literature, such as microscopic images of the shell and spikes of the virus.
From previous studies, scientists have mapped the general structure of the coronavirus – a family of viruses that are HIV, influenza, and the novel SARS-CoV-2. This structure consists of a smooth shell of lipid proteins, and dense spike-filled receptors that exit from the shell.
With this geometry in mind, the team modeled the virus as a thin elastic shell covered in about 100 elastic spikes. Given the exact physical properties of the virus, the researchers simulated the behavior of this simple structure over a range of elasticities for both the shell and the spikes.
“We don’t know what the material properties of the spikes are because they are so tiny – about 10 nanometers high,” says Wierzbicki. “Even more unknown is what is inside the virus, which is empty but full of RNA, which itself is surrounded by a protein capsid shell. So this modeling needs a lot of assumptions. ”
“We feel confident that this elastic model is a good place to start,” says Wierzbicki. “The question is, what weights and rays will cause the virus to fall?”
Corona fall
To answer that question, the researchers incorporated acoustic vibrations into the simulations and observed how the vibrations passed through the structure of the virus over a range of ultrasound frequencies.
The team started with vibrations of 100 megahertz, or 100 million cycles per second, which they estimated would be the natural vibration frequency of the shell, based on what we know about the physical properties of the virus.
When they exposed the virus to 100 MHz ultrasound invitations, the natural vibrations of the virus were not initially unknown. But within a millisecond fraction, the external vibrations, rising with the frequency of the virus’ natural oscillations, caused the shell and spikes to invade, resembling a ball that tumbling while kicking off the ground.
As the researchers increased the magnitude, or intensity, of the vibrations, the shell could break – an acoustic phenomenon called resonance that also explains how opera singers can crack a wine glass if they singing at the right level and at the right size. At lower frequencies of 25 MHz and 50 MHz, the virus pushes and breaks down even faster, both in typical air environments, and in water that is similar in density to liquids in the body. .
“These frequencies and depths are within the range that is safely used for medical imaging,” says Wierzbicki.
To update and validate their simulations, the team is working with microbiologists in Spain, who are using an atomic force microscope to monitor the effects of ultrasound vibrations on a type of coronavirus found only in pigs. If ultrasound is experimentally tested to rule out damage to coronaviruses, including SARS-CoV-2, and if this damage is proven to have a therapeutic effect, the team finds that ultrasound , which is already used to break down kidney stones and release drugs through liposomes, which could be used to treat and possibly prevent coronavirus infection. The researchers also speculate that miniature ultrasound transducers, equipped in phones and other portable devices, may be able to protect people from the virus.
Wierzbicki confirms that much more research needs to be done to determine whether ultrasound can be an effective treatment and prevention strategy against coronaviruses. As his team works to improve the existing simulations with new experimental data, he expects zero in on the novel’s unique mechanics, the fast-moving SARS-CoV-2 virus. .
“We looked at the general coronavirus family, and now we’re looking specifically at the morphology and geometry of Covid-19,” Wierzbicki says. “The potential is something that could be great in the current emergency situation.”