The virucidal effects of 405 nm visible light on SARS-CoV-2 and influenza A virus

Abstract

Germicidal potential of specific wavelengths within the electromagnetic spectrum is an area of growing interest. While ultra-violet (UV) based technologies have shown satisfactory virucidal potential, the photo-toxicity in humans coupled with UV associated polymer degradation limit its use in occupied spaces. Alternatively, longer wavelengths with less irradiation energy such as visible light (405 nm) have largely been explored in the context of bactericidal and fungicidal applications. Such studies indicated that 405 nm mediated inactivation is caused by the absorbance of porphyrins within the organism creating reactive oxygen species which result in free radical damage to its DNA and disruption of cellular functions. The virucidal potential of visible-light based technologies has been largely unexplored and speculated to be not effective given the lack of porphyrins in viruses. The current study demonstrated increased susceptibility of lipid-enveloped respiratory pathogens of importance such as SARS-CoV-2 (causative agent of COVID-19) as well as the influenza A virus to 405nm, visible light in the absence of exogenous photosensitizers, indicating a potential porphyrin-independent alternative mechanism of visible light mediated viral inactivation. Given that visible light is generally safe to humans, our results support further exploration of the use of visible light technology for the application of continuous decontamination in areas within hospitals and/or infectious disease laboratories, specifically for the inactivation of respiratory pathogens such as SARS-CoV-2 and Influenza A.

High Intensity Violet Light (405 nm) Inactivates Coronaviruses in Phosphate Buffered Saline (PBS) and on Surfaces

“…The required log irradiation doses for this bovine coronavirus noted here were about an order of magnitude higher than results for SARS-CoV-2 [26,27] and about a factor of 2.5 higher than the results for feline infectious peritonitis virus, another animal coronavirus [54]. However, our determined log reduction doses seem to be roughly in the same order of magnitude than the recent results of Enwemeka et al, who irradiated the human coronaviruses HCoV-229E and HCoV-OC43 with pulsed violet and blue light and observed a 2.37 and 1.46 log reduction with pulsed 405 nm irradiation, respectively [55].…”

“…However, published reports exist [26,27] that SARS-CoV-2, in particular, is quite sensitive to visible violet light, with D90 doses (90% reduction dose) in the range of only a few J/cm 2 , which would correspond to a much higher sensitivity than that reported in bacteria. This would be highly encouraging for the containment of the coronavirus pandemic, but it must be ensured that these results do not depend on the media applied during the irradiation.…”

Direct inactivation of SARS‐CoV‐2 by low level blue photobiomodulation LED at 470, 454 and 450 nm

“…Another study recently conducted by Rathnasinghe [11] explored the impact of 405 nm light on SARS‐CoV‐2, obtaining viral inactivation with an irradiance ranging from 0.035 to 0.6 mW/cm 2 . The authors irradiated the virus for 24 h and observed a reduction after at least 4 h of illumination.…”

“…To note, in the context of disinfection and decontamination classical ultraviolet lamps are generally regarded as a highly efficient and well‐established tool. Nevertheless, these devices possess some nonnegligible limitations such as the inability to penetrate deeply into fluids, the induction of polymer degradation, and the emergence of phototoxic responses in humans [11]. The setting of our experimental model allowed us to overcome the previously described limitations by employing blue LED light.…”