17 June 2020
AquiSense’s UV-C LED lamps used by University of Miyazaki to determine UV dose response for SARS-CoV-2
Nikkiso Group company AquiSense Technologies LLC of Erlanger, KY, USA says that its UV-C LEDs (with a peak wavelength of 280nm) have been used by Japan’s University of Miyazaki to irradiate SARS-CoV-2 virus (which causes COVID-19) isolated from the Diamond Princess cruise ship (which saw many cases early in the pandemic) in order to determine a UV dose response curve.
“This work certainly bolsters the case for the use of UV-C LEDs for societal benefit against SARS-CoV-2,” says chief technology officer Jennifer Pagan Ph.D. “Considering the large number of research projects underway exploring the efficacy of UV-C on the virus, we can expect the supporting body of evidence to only increase,” she adds.
The study used an infectivity assay on Vero cells to measure the inactivation of SARS-CoV-2 under UV-C LED irradiation. By varying the exposure time for each sample, the researchers were able to generate a series of datapoints (a dose response curve). Data such as these are used throughout the UV industry, allowing system designers to match a target UV exposure to a desired degree of inactivation. This study is the first demonstration of a UV dose response curve for SARS-CoV-2.
Graphic: Replotting of the data presented by Inagaki et al (2020). The low initial concentration of viral particles in the study impacted measurement of the inactivation effect at all doses above 7.5mJ cm-2.
Analysis of these data gives a D90 value (the UV dose required to achieve a 90% reduction) in the 4.2–5.3mJ cm-2 range, indicating that SARS-CoV-2 may be more susceptible to UV exposure than other common viruses such as norovirus. However, a low starting concentration of the virus limited the maximum inactivation that could be measured to 3.3-log (99.95%) and may have resulted in an effect known as ‘tailing’. Both features limit conclusions that can be drawn from the data.
“The more we learn about the way this virus behaves, the better we can design systems to combat it effectively,” says Rich Simons Ph.D, head of Application Science at AquiSense. “This study is certainly not the end of discussion on UV as a tool for SARS-CoV-2 inactivation but adds a useful datapoint to our ongoing analysis and gives us confidence that we’re on the right track.”