Antibacterial and antibiofilm effects of immobilized hydrogen on pathogenic oral bacteria

Hydrogen, a colorless and odorless gas, possesses various physiological activities, including anti-inflammatory, antibacterial, antioxidant, anti-cancer, and anti-apoptotic effects. Clinical applications of hydrogen have been investigated in the medical field. However, few studies have focused on hydrogen use in dentistry and its clinical applications have not yet progressed. This study aimed to evaluate the antibacterial and antibiofilm efficacies of hydrogen-loaded coral calcium carbonate powder (immobilized hydrogen) against pathogenic oral bacteria.

Three immobilized hydrogen suspensions (TU-A, -B, and -C) and three pathogenic oral bacteria (Porphyromonas gingivalis, Streptococcus mutans, and Enterococcus faecalis) were used. The direct and indirect antibacterial effects of immobilized hydrogen were evaluated by counting the colony-forming units. The biofilm-related gene expression levels in E. faecalis were analyzed using real-time RT-PCR. The antibacterial activity of the bacteria in the biofilm was observed under a fluorescence microscope after live/dead staining. All immobilized hydrogen suspensions significantly reduced the survival rates of the three oral bacteria, significantly increased the proportion of dead bacteria in the biofilm, and significantly decreased the biofilm-related gene expression levels in E. faecalis.

This study highlights the potential of immobilized hydrogen as a novel antibacterial material, owing to its antibacterial and antibiofilm activities against pathogenic oral bacteria.