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

Abstract

Antimicrobial photodynamic therapy (a-PDT) is a promising anti-infective technique for generation of singlet oxygen (1O2) to target dental disease. However, conventional organic photosensitizers have 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) 1O2 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 1O2 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 1O2 and Ag+ ions coupled with low cytotoxicity.

• Authors: Kanako Shitomi, Hirofumi Miyaji, Saori Miyata, Tsutomu Sugaya, Natsumi Ushijima, Tsukasa Akasaka, Hideya Kawasaki
• Journal: Photodiagnosis and photodynamic therapy (Photodiagnosis Photodyn Ther) Vol. 30 Pg. 101647 (Jun 2020) ISSN: 1873-1597 [Electronic] Netherlands
• PMID: 31904554 (Publication Type: Journal Article)
• Copyright: Copyright © 2020 Elsevier B.V. All rights reserved.

Chemical References

• Photosensitizing Agents
• Rose Bengal
• Silver

Topics

• Animals
• Mice
• NIH 3T3 Cells
• Nanocomposites
• Photochemotherapy (methods)
• Photosensitizing Agents (pharmacology)
• Rose Bengal (pharmacology)
• Silver (pharmacology)