Much like the laser weapons used in sci-fi battles, ultraviolet-C (UVC) irradiation is a powerful way to vanquish disease-causing microbes on surfaces, such as door handles. UVC inactivates bacteria and viruses by destroying their molecular components.
New irradiation technologies, such as 277 nm UVC light-emitting diodes (LEDs) and 222 nm far UVC sources, are gaining traction as potentially safer and more efficient alternatives to the traditional 254 nm UVC mercury lamps used in hospitals. However, there is limited evidence for how these different methods stack up when it comes to inactivating coronaviruses.
To better prepare for future outbreaks, Research Director Weiping Han and Senior Scientist Qunxiang Ong at A*STAR’s Institute of Molecular & Cell Biology (IMCB) partnered with colleagues at IMCB and the Singapore Institute of Manufacturing Technology (SIMTech) to conduct the first head-to-head analysis of various UVC wavelengths against human coronaviruses.
The team chose two human coronavirus models: hCOV-OC43, which shares similar spike protein structures to SARS-CoV-2, and hCoV-229E, a coronavirus that resembles the common cold virus.
Han and colleagues used three different UVC light sources (277 nm UVC LED, 222 nm far UVC and a 254 nm UVC mercury lamp) to treat the coronaviruses before assessing virus infectivity in human lung cell cultures.
“To our surprise, the 277 nm UVC LED performed better than the other UVC wavelengths tested,” said Ong. While the 254 nm UVC mercury lamp was found to cause relatively greater damage to viral genomes, 277 nm UVC LED irradiation led to a more pronounced degradation of the spike protein.
“These are the key proteins exposed on the external surface of coronaviruses and are responsible for viral transmission by binding to the host receptors,” Ong clarified. “This could potentially explain why 277 nm UVC LED is more effective in deactivating coronaviruses.”
In addition to being a promising disinfection tool for coronaviruses, 277 nm UVC LEDs offer the advantage of being easily integrated into portable devices, requiring shorter irradiation times and eliminating the need for highly restricted mercury-based lamps.
These findings show for the first time how the effectiveness of UVC disinfection depends on the way different wavelengths interact with viral components. Ong emphasised that selecting an optimal UVC wavelength also depends on the chemical properties of the surface materials to be disinfected.
Ong said that a similar approach can better prepare us for handling future infectious disease outbreaks. “In the event of future pandemics, we can study the composition of the viruses and decide on the best disinfection strategy to be adopted,” Ong suggested.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Molecular & Cell Biology (IMCB) and the Singapore Institute of Manufacturing Technology (SIMTech).