Photodynamic inactivation of oral bacteria with silver nanoclusters/rose bengal nanocomposite.

Research paper by Kanako K Shitomi, Hirofumi H Miyaji, Saori S Miyata, Tsutomu T Sugaya, Natsumi N Ushijima, Tsukasa T Akasaka, Hideya H Kawasaki

Indexed on: 08 Jan '20Published on: 07 Jan '20Published in: Photodiagnosis and Photodynamic Therapy


Antibacterial photodynamic therapy (a-PDT) is a promising anti-infective technique for generation of singlet oxygen (O) to target dental disease. However, conventional organic photosensitizers have some problems for clinical use in terms of cytotoxicity, quenching of a-PDT activity by self-dimerization, and the lack of long-term antibacterial effect. We herein propose silver nanoclusters/rose bengal nanocomposite (AgNCs/RB) as a novel photosensitizer with two primary antibacterial effects: (1) O generation by irradiated RB and (2) Ag ion release from AgNCs. AgNCs/RB irradiated with white light-emitting diode (LED) for a short irradiation time of 1 min significantly decreased the bacterial turbidity of Streptococcus mutans, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans (P < 0.05). In SEM, TEM and LIVE/DEAD staining images, photoexcited AgNCs/RB reduced S. mutans colonization, destroyed the cell membrane, and increased the number of dead cells. The antibacterial efficiency of photoexcited AgNCs/RB was greater than that of AgNCs or RB alone (P < 0.05), suggesting a synergistic effect of O and Ag + ions from photoexcited AgNCs/RB. By contrast, photoexcited AgNCs/RB did not affect WST-8 and LDH activities and morphology of NIH3T3 mammalian cells, indicating low cytotoxicity. Interestingly, the antibacterial activity of AgNCs/RB on S. mutans was maintained even after the cessation of LED irradiation, indicating a long-term antibacterial effect due to released Ag ions. The present AgNCs/RB photosensitizers provide effective synergistic antibacterial effects for dental a-PDT via O and Ag ions coupled with low cytotoxicity. Copyright © 2020. Published by Elsevier B.V.