Suppression of airborne viral epidemic spread by UVC light barriers

The use of light for sterilization is very well known in the scientific literature. However, the recent pandemic outbreak and the antimicrobial resistance question drew attention to this topic: to design new light sources for preventing viral epidemic spread is of utmost importance, as an alternative use of chemicals and drugs. Here we present the preliminary ex vivo studies aiming at verifying the potential of new UVC light sources as barriers to the spread of airborne viruses and bacteria. The emitted light is at very short wavelengths (around 220 nm): optical penetration in biological media is limited to a few micrometers, thus preventing the possible damages to the skin and the cornea; the absorption of RNA/DNA shows a minimum at 230 nm, increasing at shorter wavelengths. In this study we optimized a UVC commercial excimer lamp to design a light barrier. The sterilization efficacy has been tested in vitro in cultured Staphylococcus aureus, Pseudomonas aeruginosa and in Sars-Cov-2. The results point out a strong antimicrobial effect (>99.9% bacteria reduced) at ~15 mJ/cm2 (corresponding to 1 minute treatment time @0.25 mW/cm2 ). The designed prototype can thus be proposed as a light barrier for preventing contamination, reducing the risks for human beings.