Microbicidal effect of deep ultraviolet light-emitting diode irradiation
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BRIEF REPORT
Microbicidal effect of deep ultraviolet light-emitting diode irradiation Tatsuya Takagi 1 & Jun Nishikawa 1 & Masashi Yanagihara 2 & Soichiro Fukuda 1 & Naoto Kubota 1 & Yuki Kobayashi 1 & Ken-ichiro Otsuyama 1 & Junzo Nojima 1 & Hidehiro Tsuneoka 1 & Kohei Sakai 3 & Yutaka Suehiro 3 & Takahiro Yamasaki 3 & Kenji Sakurai 4 & Kazuki Itatani 5 & Isao Sakaida 6 Received: 11 June 2020 / Accepted: 4 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Introduction A light-emitting diode (LED) is a semiconductor light source with a structure called a positive-negative (p-n) junction in which a p-type and an n-type semiconductor are combined. When a voltage is applied, electrons in the p-type semiconductor recombine with electron holes in the n-type semiconductor, releasing energy in the form of photons [1]. LEDs have been used as light sources with unique characteristics of portability, power efficiency, low heat production, and durability [2]. The color of the emitted light depends on the semiconductor materials. LEDs are generally classified into three types: ultraviolet, visible, and infrared. In 2008, a deep ultraviolet (DUV)-LED composed of GaN and AlN was developed that emits light at a wavelength of 200 to 300 nm [3]. Lowpressure mercury lamps emitting light of the DUV region are used to sterilize bacteria and viruses in water, air, and food [4]. However, the Minamata Convention on Mercury
* Jun Nishikawa [email protected]
prohibits the manufacture, export, and import of mercurycontaining products by 2020 [5]. Thus, DUV-LEDs are expected as alternative light sources for mercury lamps. Microbicidal effects of DUV-LEDs have recently been reported, but differences in microbicidal effects depending on microorganism types are unknown. We investigated the microbicidal effect of DUV-LEDs in various bacteria including spore and yeast forms.
Materials and methods Microorganism strains and growth conditions Escherichia coli NBRC3972, Pseudomonas aeruginosa NBRC13275, Staphylococcus aureus NBRC13276, Bacillus subtilis NBRC3134, and Candida albicans NBRC1594 were purchased from National Institute of Technology and Evaluation (NITE) Biological Resource Center (NBRC, Japan). Bacteria were cultured on heart infusion (HI) agar (Eiken Kagaku, Japan) at 37 °C, whereas C. albicans was cultured on Sabouraud agar (Eiken Kagaku, Japan) at 30 °C. After 16-h incubation for bacteria and 48-h incubation for C. albicans, cell suspensions were prepared using phosphate-buffered saline (PBS).
1
Faculty of Laboratory Science, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-kogushi, Ube 755-8505, Japan
2
Department of Surgery and Clinical Science, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan
Preparation of spore suspension
3
Department of Oncology and Laboratory Medicine, Yamaguchi University Graduate School of Medicine, Ube, Japan
4
R&D Department, Research and Technology Development Unit, CCS Inc., Kyoto, Japan
5
Device Technology and Product Develo
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