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. 2021 Sep 30;11(1):19470.
doi: 10.1038/s41598-021-97797-0.

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

Raveen Rathnasinghe  1   2   3 , Sonia Jangra  1   2 , Lisa Miorin  1   2 , Michael Schotsaert  1   2 , Clifford Yahnke  4 , Adolfo Garcίa-Sastre  5   6   7   8
Affiliations

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

Raveen Rathnasinghe et al. Sci Rep. .

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.

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Conflict of interest statement

The García-Sastre Laboratory has received research support from Pfizer, Senhwa Biosciences, 7Hills Pharma, Avimex, Blade Therapeutics, Dynavax, ImmunityBio, Nanocomposix and Kenall Manufacturing. Adolfo García-Sastre has consulting agreements for the following companies involving cash and/or stock: Vivaldi Biosciences, Pagoda, Contrafect, 7Hills Pharma, Avimex, Vaxalto, Accurius, Pfizer and Esperovax. RR, CY and AGS have filed for a provisional patent based upon these results.

Figures

Figure 1
Figure 1
Inactivation device setup and characterization. (A) Test setup shown with spectroradiometer, and extension used for calibration. (B) Test setup showing the placement of the control and sample for irradiation. The bottom portion of the test rig was removed during the actual experiment to ensure the 10″ distance used in the study. (C) Normalized spectral power distribution showing peak irradiance at 405 nm. (D) Normalized spectral power distribution for the fluorescent control light (non-disinfecting) and standard LED light (without 405 nm) used in the study. Each spectrum is normalized relative to its own peak value.
Figure 2
Figure 2
Dose and time dependent inactivation of SARS-CoV-2 virus in PBS by 405 nm irradiation. (A) A dose of 0.035 mW cm−2 or (B) a dose of 0.076 mW cm−2 or (C) a dose of 0.150 mW cm−2 or (D) a dose of 0.6 mW cm−2 was applied to irradiate samples at 405 nm over a course of 24 while sampling at 4, 8, 12 and 24 h (for A, B and C) or over a course of 8 h while sampling at 1, 2, 4 and 8 h (D) was done in independent triplicates. Blue bars indicate treated samples and red bars correspond to the untreated equivalent that was left at the biosafety cabinet under the same conditions while not subjecting to disinfecting irradiation. Data shown as PFUml−1 in triplicate assessed by plaque assay. (E) Plaque phenotype comparison from one independent experiment at an irradiation dose of 0.6 mW cm−2. Fixed and blocked plaques were immunostained using anti-SARS-CoV-2/NP antibody before developing using TrueBlue reagent. Data show in here are from three independent replicates (Mean + SEM).
Figure 3
Figure 3
Inactivation of Influenza A virus in PBS by 405 nm irradiation. (A) A dose of 0.6 mW cm−2 was applied to irradiate samples at 405 nm over a course 8 h while sampling at 1, 2, 4 and 8 h (done in independent triplicates). Blue bars indicate treated samples and red bars correspond to the untreated equivalent that was left at the biosafety cabinet under the same conditions while not subjected to disinfecting irradiation. Data shown as PFUml−1 in triplicate assessed by plaque assay. (B) Plaque phenotype comparison from one independent experiment at an irradiation dose of 0.6 mW cm−2. Fixed and blocked plaques were stained using crystal violet. Data show in here are from three independent replicates (Mean + SEM).
Figure 4
Figure 4
Encephalomyocarditis virus (EMCV) in PBS shows reduced susceptibility to 405 nm irradiation. (A) A dose of 0.6 mW cm−2 was applied to irradiate samples at 405 nm over a course 8 h while sampling at 1, 2, 4 and 8 h (done in independent triplicates). Blue bars indicate treated samples and red bars correspond to the untreated equivalent that was left at the biosafety cabinet under the same conditions while not subjected to disinfecting irradiation. Data shown as PFUml−1 in triplicate assessed by plaque assay. (B) Plaque phenotype comparison from one independent experiment at an irradiation dose of 0.6 mW cm−2. Fixed and blocked plaques were stained using crystal violet. Data show in here are from three independent replicates (Mean + SEM).
Figure 5
Figure 5
Inactivation potential for SARS-CoV-2 using standard LED lighting containing spectral wavelengths from 400 to 420 nm. Standard LED lights were used to irradiate samples over a course 24 h while sampling at 4, 8, 12 and 24 h (done in independent triplicates). Blue bars indicate treated samples and red bars correspond to the untreated equivalent that was left at the biosafety cabinet under the same conditions while not subjected to disinfecting irradiation. Data shown as PFUml−1 in triplicate assessed by plaque assay.
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