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

Abstract

The 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 their 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 ineffective 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) and influenza A virus to 405 nm, visible light in the absence of exogenous photosensitizers thereby indicating a potential alternative porphyrin-independent mechanism of visible light mediated viral inactivation. These results were obtained using less than expected irradiance levels which are considered safe for humans and commercially achievable. Our results support further exploration of the use of visible light technology for the application of continuous decontamination in occupied areas within hospitals and/or infectious disease laboratories, specifically for the inactivation of respiratory pathogens such as SARS-CoV-2 and Influenza A.

Review of Virus Inactivation by Visible Light

“…Most of the new coronavirus studies do not discuss this possibility. Rathnasinghe et al have mentioned a comparative study with a riboflavin solution but published no results [42].…”

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

“…To note, in the context of disinfection and decontamination classical ultraviolet lamps are generally regarded as a highly efficient and wellestablished 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.…”

“…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.…”

Blue Laser Light Counteracts HSV-1 in the SH-SY5Y Neuronal Cell Model of Infection

“…Rathnasinghe et al [27] explored the effect of 405 nm light with irradiance from 0.035 to 0.6 mW/cm 2 on SARS-CoV-2, obtaining viral inactivation after at least 4 h of illumination. Although the irradiance was very low from that tested in the current study, and in the other research described above, the total energy reached very high levels.…”