Skin tolerant inactivation of multiresistant pathogens using far-UVC LEDs
Multiresistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) cause serious postoperative infections. Porcine skin irradiated with a dose of 40 mJ/cm2 at 233 nm showed only 3.7% CPD and 2.3% 6-4PP DNA damage. Corresponding irradiation at 254 nm caused 15–30 times higher damage.
Thus, the skin damage caused by the disinfectant doses is so small that it can be expected to be compensated by the skin’s natural repair mechanisms. LED-based far-UVC lamps could therefore soon be used in everyday clinical practice to eradicate multiresistant pathogens directly on humans.
UVC radiation can inactivate microorganisms and viruses by triggering photochemical reactions in the DNA or RNA. As a result, they can no longer replicate and their potential pathogenic efficacy is thus inhibited. This type of disinfection is currently used for drinking water, and also for cleaning surfaces8 and air9. The required dose for the inactivation of microorganisms and viruses depends strongly on the individual species, their environment and the wavelength of the radiation.
Generally, the UV absorption spectrum of DNA and RNA exhibits a maximum at ~ 265 nm and a minimum around ~ 240 nm and increases again for shorter wavelengths. The main advantage of using far-UVC radiation (< 240 nm) instead of near-UVC radiation (250–280 nm) for the inactivation is its lower penetration depth in the skin.
Far-UVC radiation is mainly absorbed in the uppermost, non-living cornified layer of the skin and potentially causes little damage to the living cells underneath, as previously shown in mice. This gives rise to the vision of antisepsis of skin surfaces by direct UVC irradiation without serious damage to health. This vision is supported by numerous studies conducted in recent years on the skin tolerance of far-UVC radiation.