Viricide activity of antimicrobial blue light (405 nm) against the SARS-CoV-2 and influenza virus

Abstract Background Over the years, antimicrobial blue light (aBL) at a 405 nm wavelength has emerged as a potential alternative treatment for reducing the environmental contamination. It is well accepted that aBL is much less detrimental to host cells than UV-C irradiation and can be used in the presence of people. This study aims to determine the viricide activity, against the SARS-CoV-2 and influenza virus types A and B, of the nUV-A radiation, using a customized nUV-A ceiling lamp System. Methods The experiment took place in March 2023. An nUV-A ceiling lamp prototype, composed of 9 LEDs at 405 nm, was fixed on a metal scaffold, on which the outline of a multiwell plate (24 wells) was traced to carry out the tests correctly. Each plate well was inoculated with 100 µL of SARS-CoV2 or influenza virus types A or B suspension. The multiwell plate was irradiated at 32 cm for 45 and 90 minutes, with an emitted energy dose of 12 J/cm2 and 24 J/cm2. Three samples were inoculated with viruses and subjected to the action of nUV-A as per protocol, and 3 samples were inoculated but not treated with nUV-A to determine viral titer after recovery and examined immediately after inoculation. The re-collected suspensions were used to inoculate a wells plate into which the VERO E6 cell cultures were fixed and then incubated for 3 days at 37° C. Results The results showed that after a 45 min exposition, the measurable log10 mean reduction was 1.50 for SARS-CoV2, 0.13 for influenza virus type A and 0.12 for type B; after 90 min the log10 mean reduction was 2.33 for SARS-CoV2, 0.16 for influenza virus type A and 0.17 for type B. Conclusions Tests have shown that aBL can be effective in reducing the viral load of the SARS-CoV2 virus and, to a lesser extent, the influenza A/B viruses. Disinfection with aBL appears effective and avoid the adverse effects of using UV-C. Further studies will evaluate how to improve the results on influenza viruses and the application on other viruses such as RSV. Key messages • NearUV-A lamp has proven to reduce the virucide activity of all viruses, more for sars-cov2. • Using aBL avoids the adverse UV-C’s effects.