Viability evaluation of layered cell sheets after ultraviolet light irradiation of 222 nm

Hanamura, Nami; Ohashi, Hiroyuki; Morimoto, Yukihiro; Igarashi, Tatsushi; Tabata, Yasuhiko

doi:10.1016/j.reth.2020.04.002

Cited by 17 publications

(15 citation statements)

References 41 publications

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“…The germinative cells in the corneal limbus are shielded by at least three cell layers (36). In the layered cell sheets, the UV transmittance of 222 nm was 10 times less than that of 254 nm (37); thus, the 222 nm UV‐C is far less likely to be a causative factor of pterygium than 254 nm. Collectively, we can indicate that the full‐room UVGI with the current study's conditions is safe for the eyes and lid skin at least for a year period.…”

Section: Discussionmentioning

confidence: 99%

One‐year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222‐nm Far Ultraviolet‐C Lamps

Sugihara

Kaidzu

Sasaki

et al. 2022

Photochem & Photobiology

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Two krypton‐chloride germicidal excimer lamp units (Care222 TRT‐104C11‐UI‐U3, USHIO Inc.) were installed in the examination room of an ophthalmology department. The irradiation dose was set not to exceed the former (i.e., before 2022) threshold limit value (TLV) (22 mJ cm−2/8 h) recommended by the ACGIH. Section 1: The eyes and lids of the six ophthalmologists (5 wore glasses for myopic correction) who worked in the room for a mean stay of 6.7 h week−1 were prospectively observed for 12 months. Slitlamp examinations revealed neither acute adverse events such as corneal erosion, conjunctival hyperemia, and lid skin erythema nor chronic adverse events such as pterygium, cataract, or lid tumor. The visual acuity, refractive error, and corneal endothelial cell density remained unchanged during the study. Section 2: The irradiation of samples placed on the table or floor using the same fixtures in the room (5–7.5 mJ cm−2) was associated with >99% inhibition of φX174 phage and >90% inhibition of Staphylococcus aureus. In conclusion, no acute or chronic health effects in human participants was observed in a clinical setting of full‐room ultraviolet germicidal irradiation by 222‐nm lamp units, and high efficacy in deactivation of microorganisms was determined in the same setting.

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Section: Discussionmentioning

confidence: 99%

One‐year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222‐nm Far Ultraviolet‐C Lamps

Sugihara

Kaidzu

Sasaki

et al. 2022

Photochem & Photobiology

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“…Far-UVC radiation in the range of 200–230 nm has emerged as a promising UV disinfection tool during the COVID-19 pandemic. It can be provided via several UV radiation sources (e.g., excimer lamps and UV light-emitting diodes), among which the krypton-chloride excimer (KrCl*) lamp with an emission peak at 222 nm is the most mature and commercially available one. − The KrCl* excimer lamp has no mercury and a reasonably high wall plug efficiency (0.5–7.0%) compared to Far-UVC-LEDs (<0.5%). , It generates a negligible amount of ozone during use, , and the radiation at 222 nm is safer than 254 nm to human tissues (e.g., skin and eyes) in air/surface disinfection applications since 222 nm photons barely penetrate through the dead cell layer of skin (stratum corneum). ,− The penetration of Far-UVC in deionized water is not a problem since water molecules (H 2 O) barely absorb UV radiation at 222 nm . The UV absorption of DNA/RNA of microorganisms has been reported to be comparable (∼1 fold) at 222–254 nm, but that of proteins is much higher (∼20 fold) at 222 nm. ,− This suggests that Far-UVC may pose higher inactivation efficiency than UVC at 254 nm.…”

Section: Introductionmentioning

confidence: 99%

Nitrate Protects Microorganisms and Promotes Formation of Toxic Nitrogenous Byproducts during Water Disinfection by Far-UVC Radiation

Wang

et al. 2023

Environ. Sci. Technol.

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Far-UVC radiation is an emerging tool for combating pathogenic microorganisms in water, but its vulnerability to water matrix components remains unclear. We herein report the critical impacts of nitrate during Far-UVC disinfection of water. Nitrate at environmentally relevant concentrations (0.5−10.0 mg-N L −1 ) significantly inhibits Escherichia coli inactivation by Far-UVC radiation at 222 nm, via prolonging the "lag phase" of inactivation and reducing the inactivation rate constants by 1.08−2.74 times, while it shows negligible impact on E. coli inactivation by UVC radiation at 254 nm. The inhibitory impact of nitrate on Far-UVC disinfection is attributed to its strong light-shielding effect. Although hydroxyl radicals and reactive nitrogen species are generated from Far-UVC photolysis of nitrate at high concentrations of 10 −13 and ∼10 −7 M, respectively, those radicals are unable to compensate for the light-shielding effect of nitrate on E. coli inactivation. Moreover, reactive nitrogen species lead to the formation of nitrogenous byproducts, which increase the genotoxicity of the water. The findings advance the fundamental photochemistry and radical chemistry of nitrate at 222 nm and provide useful insights to guide the operation of Far-UVC in treating nitrate-containing water.

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“…While there is considerable evidence for far-UVC safety in skin and eyes (7,16,(18)(19)(20)22,(27)(28)(29)(30)(31), there have been no direct systematic measurements of DNA damage in skin as a function of wavelength that encompasses the far-UVC and conventional germicidal UVC wavelengths. This is important both from the perspective of directly validating the far-UVC concept, but also because in addition to the primary emission (e.g.…”

Section: Introductionmentioning

confidence: 99%

Wavelength‐dependent DNA Photodamage in a 3‐D human Skin Model over the Far‐UVC and Germicidal UVC Wavelength Ranges from 215 to 255 nm

Welch

Muro

Brenner

2022

Photochem & Photobiology

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The effectiveness of UVC to reduce airborne-mediated disease transmission is well established. However, conventional germicidal UVC (~254 nm) cannot be used directly in occupied spaces because of the potential for damage to the skin and eye. A recently studied alternative with the potential to be used directly in occupied spaces is far UVC (200-235 nm, typically 222 nm), as it cannot penetrate to the key living cells in the epidermis. Optimal far-UVC use is hampered by limited knowledge of the precise wavelength dependence of UVC-induced DNA damage, and thus we have used a monochromatic UVC exposure system to assess wavelengthdependent DNA damage in a realistic 3-D human skin model. We exposed a 3-D human skin model to mono-wavelength UVC exposures of 100 mJ/cm 2 , at UVC wavelengths from 215 to 255 nm (5 nm steps). At each wavelength, we measured yields of DNA-damaged keratinocytes, and their distribution within the layers of the epidermis. No increase in DNA damage was observed in the epidermis at wavelengths from 215 to 235 nm, but at higher wavelengths (240-255 nm) significant levels of DNA damage was observed. These results support use of far-UVC radiation to safely reduce the risk of airborne disease transmission in occupied locations.

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Viability evaluation of layered cell sheets after ultraviolet light irradiation of 222 nm

Cited by 17 publications

References 41 publications

One‐year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222‐nm Far Ultraviolet‐C Lamps

One‐year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222‐nm Far Ultraviolet‐C Lamps

Nitrate Protects Microorganisms and Promotes Formation of Toxic Nitrogenous Byproducts during Water Disinfection by Far-UVC Radiation

Wavelength‐dependent DNA Photodamage in a 3‐D human Skin Model over the Far‐UVC and Germicidal UVC Wavelength Ranges from 215 to 255 nm

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