J Li1, K Hirota, H Yumoto, T Matsuo, Y Miyake, T Ichikawa. 1. Department of Oral and Maxillofacial Prosthodontics and Oral Implantology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
Abstract
AIMS: The major objective of the study was to evaluate the enhanced germicidal effects of low-frequency pulsed ultraviolet A (UVA)-light-emitting diode (LED) on biofilms. METHODS AND RESULTS: The germicidal effects of UVA-LED irradiation (365 nm, 0·28 mW cm(-2) , in pulsed or continuous mode) on Candida albicans or Escherichia coli biofilms were evaluated by determining colony-forming units. The morphological change of microbial cells in biofilms was observed using scanning electron microscopy. After 5-min irradiation, over 90% of viable micro-organisms in biofilms had been killed, and pulsed irradiation (1-1000 Hz) had significantly greater germicidal ability than continuous irradiation. Pulsed irradiation (100 Hz, 60 min) almost completely killed micro-organisms in biofilm (>99·9%), and 20-min irradiation greatly damaged both microbial species. Interestingly, few hyphae were found in irradiated Candida biofilms. Moreover, mannitol treatment, a scavenger of hydroxyl radicals (OH(•) ), significantly protected viable micro-organisms in biofilms from UVA-LED irradiation. CONCLUSIONS: The study demonstrated that pulsed UVA-LED irradiation has a strong germicidal effect (maximum at 100 Hz, over 5-min irradiation) and causes the disappearance of hyphal forms of Candida. SIGNIFICANCE AND IMPACT OF THE STUDY: This study can assist in developing a low-frequency pulsed UVA-LED system to be applied to pathogenic biofilms for disinfection.
AIMS: The major objective of the study was to evaluate the enhanced germicidal effects of low-frequency pulsed ultraviolet A (UVA)-light-emitting diode (LED) on biofilms. METHODS AND RESULTS: The germicidal effects of UVA-LED irradiation (365 nm, 0·28 mW cm(-2) , in pulsed or continuous mode) on Candida albicans or Escherichia coli biofilms were evaluated by determining colony-forming units. The morphological change of microbial cells in biofilms was observed using scanning electron microscopy. After 5-min irradiation, over 90% of viable micro-organisms in biofilms had been killed, and pulsed irradiation (1-1000 Hz) had significantly greater germicidal ability than continuous irradiation. Pulsed irradiation (100 Hz, 60 min) almost completely killed micro-organisms in biofilm (>99·9%), and 20-min irradiation greatly damaged both microbial species. Interestingly, few hyphae were found in irradiated Candida biofilms. Moreover, mannitol treatment, a scavenger of hydroxyl radicals (OH(•) ), significantly protected viable micro-organisms in biofilms from UVA-LED irradiation. CONCLUSIONS: The study demonstrated that pulsed UVA-LED irradiation has a strong germicidal effect (maximum at 100 Hz, over 5-min irradiation) and causes the disappearance of hyphal forms of Candida. SIGNIFICANCE AND IMPACT OF THE STUDY: This study can assist in developing a low-frequency pulsed UVA-LED system to be applied to pathogenic biofilms for disinfection.
Authors: Jonathan B Gillespie; Michelle Maclean; Martin J Given; Mark P Wilson; Martin D Judd; Igor V Timoshkin; Scott J MacGregor Journal: Photomed Laser Surg Date: 2016-10-19 Impact factor: 2.796
Authors: Renata T Kashiwabuchi; Fabio R S Carvalho; Yasin A Khan; Flavio Hirai; Mauro S Campos; Peter J McDonnell Journal: Graefes Arch Clin Exp Ophthalmol Date: 2012-11-25 Impact factor: 3.117