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

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

doi:10.1016/j.reth.2020.04.002

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

Regen Ther. 2020 May 27:14:344-351. doi: 10.1016/j.reth.2020.04.002. eCollection 2020 Jun.

Authors

Nami Hanamura^{1

2}, Hiroyuki Ohashi¹, Yukihiro Morimoto¹, Tatsushi Igarashi¹, Yasuhiko Tabata²

Affiliations

¹ Ushio Inc., Marunouchi 1-6-5, Chiyoda-ku, Tokyo, Japan.
² Laboratory of Biomaterials, Department of Regeneration Science and Engineering, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Kawara-cho Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Abstract

Introduction: The objective of this study was to evaluate the cell viability of layered cell sheets, irradiated with 222 nm UV light.

Methods: UV transmittance of 222 nm and 254 nm was evaluated when the cell sheets of NCTC Clone 929 cells were irradiated UV light. Cell viability was evaluated after irradiation of 222 nm using 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. Following irradiation of two layered cell sheets at 500 mJ/cm², the cell damage of lower layers was evaluated by a colony formation and MTT assays.

Results: The UV transmittance of 222 nm was 10 times less than that of 254 nm. A MTT assay revealed that cells of cell sheets irradiated at 222 nm was less damaged than those at 254 nm, when irradiated at 5 mJ/cm². Cell colonies were formed for cells of lower layers irradiated at 222 nm whereas no colony formation was observed for those irradiated at 254 nm. Significantly higher MTT activity was observed for cells of lower layers irradiated at 222 nm than at 254 nm.

Conclusions: It is concluded that 222 nm irradiation is biologically safe for cell viability.

Keywords: 3D, 3-dementional; CPDs, cyclobutane-pyrimidine dimers; Cell sheet; Cellular viability; H2O2, hydrogen peroxide; Kr–Cl, krypton-chloride; MTT, 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide; PBS, phosphate-buffered saline; SD, standard deviation; Sterilization; UV.