Among the many challenges we face with the spread of COVID-19 is the ability of the coronavirus to survive on surfaces for long periods of time.
While we can effectively wipe down items or sterilize them with alcohol, what about more delicate surfaces like cardboard?
Even in the atmosphere, SARS-CoV-2 can survive for up to several hours; on cardboard it can last up to 24 hours, and viable particles are found on plastic within three days after it is contaminated.
Scientists from many disciplines are investing enormous resources in the fight against the pandemic. Now, a team led by engineer Jitong Chen of UCLA may have found a solution. They have just demonstrated the ability of cold plasma to kill the virus on a wide variety of surfaces without damaging the material.
“Everything we use comes from the air,” explains aerospace engineer Richard Wirtz. 'Air and electricity: This is a very healthy procedure with no side effects.'
Plasma, the least studied of the four basic states of matter (the other three are solid, liquid, and gaseous), naturally arise in the upper atmosphere. It forms when electrons detach from their atoms (making the atoms positively charged) and together create a soup of charged particles that are unstable and therefore more reactive than their equivalent gas state.
Cold plasma has already been shown to work against drug-resistant bacteria. It disrupts the structure of their surface and DNA without damaging human tissue. It even works against cancer cells.
Chen, Wirtz, and colleagues have developed and 3D printed an atmospheric plasma jet device that uses argon gas, an inert and stable element that is one of the most common gases in our air. The device sends accelerating electrons through the gas, separating the gas atoms from the outer electrons when they collide; requires only 12 watts of continuous power to operate.
(Chen et al, Physics of Fluids, 2020).
The team directed a stream of near room temperature reactive particles onto contaminated surfaces, exposing them to electric current, charged atoms and molecules (ions), and UV radiation.
They tested the effect of plasma on six surfaces, including cardboard, leather, plastic and metal, and found that on each surface, most of the viral particles were inactivated after just 30 seconds. Three minutes of contact with plasma destroyed the virus completely.
Researchers believe that the reactive oxygen and nitrogen ions produced by the interaction of plasma with air destroy viral particles; when they tested helium-fueled plasma, which produces fewer of these kinds of atoms, it proved ineffective even after five minutes of use.
When charged particles collect on the surface of the virion, they can damage its shell due to electrostatic forces leading to its rupture. Ions can also break structurally important bonds, such as bonds between two carbon atoms, carbon and oxygen, and carbon and nitrogen atoms.
Experiments on the effects of plasma on bacteria and viruses have shown that damage to the outer envelope of the virus can include proteins important for binding to cells.
“The results also suggest that cold plasma should be tested for inactivation of the aerosol-borne SARS-CoV-2,” Wirtz and colleagues wrote in their paper.
“This is just the beginning,” Wirtz said. “We are confident and have high hopes for plasma in the future.”
The research is published in the journal Physics of Fluids.
Sources: Photo: (Kovalova Z. et al.).
