Application of 233 nm far-UVC LEDs for eradication of MRSA and MSSA and risk assessment on skin models

Abstract

A newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280–380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm2, the 233 nm light source reduced the viable microorganisms by a log10 reduction (LR) of 5 log10 levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5–3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.

Far‐UVC‐ and UVB‐induced DNA damage depending on skin type

“…Following the increased interests in room disinfection and skin antisepsis during the COVID-19 pandemic, studies have been conducted to prove the bactericidal [1][2][3][4][5][6] and virucidal 7-9 potential of far-UVC radiation (100-240 nm). UVC radiation (100-280 nm) is known to be absorbed by nucleic acids and proteins.…”

Treatment of the Candida subspecies Candida albicans and Candida parapsilosis with two far‐UVC sources to minimise mycoses in clinical practice

“…Furthermore, 233 nm produces no or only little superficial DNA damage in excised human skin and reconstructed human epidermal (RHE) skin models up to 60 mJ/cm 2 in comparison to the same irradiation dose at 254 nm (≥factor 20); moreover, the DNA damage is below 0.1 of the minimal erythema dose UVB, which is considered acceptable. After 24 h, the DNA damage degraded completely in the RHE; multiple irradiation on four consecutive days with 60 mJ/cm 2 shows no detectable DNA damage 11 …”

“…After 24 h, the DNA damage degraded completely in the RHE; multiple irradiation on four consecutive days with 60 mJ/cm 2 shows no detectable DNA damage. 11 In this study, UVC irradiation at 233 nm was compared with 222 nm for its eradicating effect on the species C. albicans and C. parapsilosis; 254 nm served as a positive control for the possibility of complete eradication.…”

Far-UVC Radiation for Disinfecting Hands or Gloves?

“…However, almost 20 years ago, Sosnin et al [ 6 ] found that there is short-wavelength UVC radiation, which damages eukaryotic cells less than prokaryotic cells. Meanwhile, it has been found that human skin tolerates UV radiation in the so-called far-UVC range of about 200–230 nm relatively well [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. This radiation is almost completely absorbed in the stratum corneum and does not reach deeper skin layers.…”