Near-infrared Irradiation and Graphene Oxide Film Fabricated on Dentin Surface Exhibit Photothermal and Antibacterial Effects

Background and objectives: Graphene oxide (GO) is a monolayer sheet of carbon with a thickness of 1 nm or less. Recent studies have revealed that GO exerts antibacterial properties, absorbs near-infrared (NIR) irradiation and generates heat. In this study, we fabricated a GO film on a human dentin block and investigated the photothermal and antibacterial effects of GO and NIR irradiation against Streptococcus mutans. Methods: The dentin block was immersed in GO dispersion (concentration: 0, 1 and 10 μg/mL). GO-coated dentin blocks were observed using scanning electron microscopy (SEM) and characterized using the dentinal tubule sealing score. The temperature increase of the GO-coated dentin surface following NIR irradiation was examined by thermography. Furthermore, antibacterial effects of the combination of GO film and NIR irradiation against S. mutans were evaluated by SEM observation, turbidity measurement, colony formation assessment and live/dead staining. Results: A thin GO film with a thickness of a few nanometers was successfully formed on the dentin surface. The dentinal tubule sealing score increased in a GO concentration-dependent manner. Even after ultrasonic cleaning, GO residue was frequently observed on the dentin surface. When the GO-coated dentin block was irradiated with NIR light, the temperature of the dentin block surface increased in a GO concentration- and time-dependent manner. In antibacterial assessments, turbidity and colony formation were suppressed by GO and NIR irradiation. In addition, dead bacteria were detected by live/dead staining. Conclusion: A stable GO film was successfully formed on the dentin surface by immersion in GO dispersion. Photothermal and antibacterial effects were remarkably exhibited by GO and NIR irradiation.