The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has had a tremendous impact on humanity. Prevention of transmission by disinfection of surfaces and aerosols through a chemical-free method is highly desirable. Ultraviolet C (UVC) light is uniquely positioned to achieve inactivation of pathogens. In a new paper in the journal ACS Photonics, scientists report the inactivation of SARS-CoV-2 virus by UVC radiation and explore its mechanisms.
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Devitt et al. demonstrated the inactivation of SARS-CoV-2 by 266-nm UVC light, which matches closely with the absorption spectra of RNA and aromatic amino acids. Image credit: Devitt et al., doi: 10.1021/acsphotonics.3c00828.
The COVID-19 pandemic caused by SARS-CoV-2 spreads via nosocomial, public, and work-place based infections.
Transmission is thought to be direct via respiratory droplets or indirect via fomites and has led to increased interest in viral disinfection.
SARS-CoV-2 viral particles are composed of a core of nucleic acid chains that contain the genetic information of the virus, surrounded by a lipid membrane with proteinous spikes sticking out. Each component is necessary for infection.
In the new study, University of Southampton’s Sumeet Mahajan and colleagues investigated how UV laser light destroys the virus by impacting each of these critical components.
By using a specialized laser at two different wavelengths, they were able to determine how each viral component degraded under the bright light.
They found the genomic material was highly sensitive to degradation and protein spikes lost their ability to bind to human cells.
UV light includes UVA, UVB and UVC light. Very little UVC light at frequencies below 280 nm reaches the Earth’s surface from the Sun.
It is this lesser studied UVC light that the authors used for their study due to its disinfectant properties.
UVC light is strongly absorbed by different viral components, including the genetic material (~260 nm) and the proteinous spikes (~230 nm), allowing the team to select laser frequencies of 266 nm and 227 nm for the project.
The researchers found that 266-nm light caused RNA damage at low powers, affecting the genetic information of the virus.
The 266-nm light also damaged the structure of the SARS-CoV-2 spike protein, reducing its ability to bind to human cells by breaking down disulphide bonds and aromatic amino acids.
The 227-nm light was less effective at inducing RNA damage, but more effective at damaging proteins through oxidation (a chemical reaction involving oxygen) which unfolds the protein’s structure.
Importantly, SARS-CoV-2 has among the largest of genomes for RNA viruses. This makes it especially sensitive to genomic damage.
“Light deactivation of airborne viruses offers a versatile tool for disinfection of our public spaces and sensitive equipment that may otherwise prove difficult to decontaminate with conventional methods,” Professor Mahajan said.
“Now we understand the differential sensitivity of molecular components in viruses to light deactivation this opens up the possibility of a finely tuned disinfection technology.”
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George Devitt et al. Mechanisms of SARS-CoV-2 Inactivation Using UVC Laser Radiation. ACS Photonics, published online December 25, 2023; doi: 10.1021/acsphotonics.3c00828
