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

Abstract

It has been proven that visible light with a wavelength of about 405 nm exhibits an antimicrobial effect on bacteria and fungi if the irradiation doses are high enough. Hence, the question arises as to whether this violet light would also be suitable to inactivate SARS-CoV-2 coronaviruses. Therefore, a high-intensity light source was developed and applied to irradiate bovine coronaviruses (BCoV), which are employed as SARS-CoV-2 surrogates for safety reasons. Irradiation is performed in virus solutions diluted with phosphate buffered saline and on steel surfaces. Significant virus reduction by several log levels was observed both in the liquid and on the surface within half an hour with average log reduction doses of 57.5 and 96 J/cm2, respectively. Therefore, it can be concluded that 405 nm irradiation has an antiviral effect on coronaviruses, but special attention should be paid to the presence of photosensitizers in the virus environment in future experiments. Technically, visible violet radiation is therefore suitable for coronavirus reduction, but the required radiation doses are difficult to achieve rapidly.

Visible 405 nm Violet-Blue Light Successfully Inactivates HIV-1 in Human Plasma

“…To our knowledge, this is the first report of 405 nm light-based inactivation of HIV-1 in human plasma. In line with the observations reported here, there have been reports of lipid-enveloped SARS-CoV-2 and Influenza A virus inactivation by 405 nm light whilst suspended in phosphate buffered saline (PBS) [13] and beta-coronaviruses (bovine) suspended in PBS as well as the virus suspension dried on steel surfaces [14]. Visible violet-blue light other than 405 nm wavelengths such as doses of 425 nm blue light were also reported to inhibit infection and replication of cell-associated SARS-CoV-2 by >99% 24 h post-infection and cell-free beta-coronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner [15].…”

Viricidal Efficacy of a 405‐nm Environmental Decontamination System for Inactivation of Bacteriophage Phi6: Surrogate for SARS‐CoV‐2

“…in the presence of exogenous photosensitizers), statistically significant 0.06 and 0.83 log 10 reductions of low‐ and high‐density populations, respectively, were observed when exposed in SM buffer, after 24 h exposure ( P ≤ 0.05); suggesting the inactivation effect is likely somewhat accountable to light interactions with the phage envelope. In addition, the doses required for a 1 log 10 reduction of high‐density populations were found to be within the same orders of magnitude of that previously established for bovine coronavirus as a surrogate for SARS‐CoV‐2 exposed in phosphate‐buffered saline, which is also absent of photosensitive material (57.5 J cm −2 in comparison with 43.2 J cm −2 found in this study) (34). Further investigation into the interactions of viral envelopes with 405‐nm light, although beyond the scope of this study, will be essential in advancing understanding of the viricidal efficacy of 405‐nm light.…”

“…The results of this study demonstrate bacteriophage phi6 can be successfully reduced when exposed in minimal SM buffer media; highlighting that 405-nm light inactivation is attainable in the absence of exogenous photosensitizers, as previously demonstrated for SARS-CoV-2 or appropriate surrogates (30,32,34,35). Due to their lack of porphyrins, viruses and bacteriophages demonstrate the lowest susceptibility of all microorganisms to 405nm light inactivation (26) and minimal inactivation has previously been indicated for non-enveloped viruses unless exposed to very high doses or suspended in organically rich media (27,28).…”

“…(30) recently demonstrated successful reductions in SARS‐COV‐2 upon exposure to low irradiance (0.035–0.6 mW cm −2 ) 405‐nm light, and additionally highlighted the increased susceptibility of lipid‐enveloped viruses in comparison with non‐enveloped viruses (identical irradiations achieved 2.3 log 10 reductions in SARS‐COV‐2 after 8 h and just 0.1 log 10 reductions in a non‐enveloped RNA virus after 24 h); suggesting the lipid envelope itself may instigate ROS production. Other studies have similarly demonstrated the susceptibility of SARS‐CoV‐2, or an appropriate surrogate, to 405‐nm light inactivation presented on surfaces and in liquid media, both in the presence and absence of photosensitizers (31–35). Although highly encouraging, these studies have primarily demonstrated inactivation using 405‐nm light at high irradiances (≥78.6 mW cm −2 ) or at low irradiances delivered at a very short distance (~2.3–25.4 cm) from the sample surface (30–35), however, it is of great importance to determine whether inactivation of SARS‐CoV‐2 can be achieved under conditions which more accurately represent those which would be safely and practically implemented for environmental decontamination of communal areas.…”

“…Other studies have similarly demonstrated the susceptibility of SARS‐CoV‐2, or an appropriate surrogate, to 405‐nm light inactivation presented on surfaces and in liquid media, both in the presence and absence of photosensitizers (31–35). Although highly encouraging, these studies have primarily demonstrated inactivation using 405‐nm light at high irradiances (≥78.6 mW cm −2 ) or at low irradiances delivered at a very short distance (~2.3–25.4 cm) from the sample surface (30–35), however, it is of great importance to determine whether inactivation of SARS‐CoV‐2 can be achieved under conditions which more accurately represent those which would be safely and practically implemented for environmental decontamination of communal areas.…”