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

Erika Nishida,Tsukasa Akasaka,Kanako Shitomi,Kayoko Mayumi,Saori Miyata,Keishi Nagao,Hirofumi Miyaji,Akihito Kato,Tsutomu Sugaya

doi:10.4172/2332-0702.1000231

Abstract

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.

Highlights

Graphene oxide (GO) exhibits a monolayer sheet of carbon with a thickness of 1 nm or less, which partly contains sp3 hybridized carbon atoms and oxygen functional groups, such as epoxy, carboxy and hydroxy groups
After ultrasonic cleaning twice with distilled water (DW) for 5 minutes, dentin blocks were sonicated with 3% ethylenediaminetetraacetic acid (EDTA) (Smearclean, Nippon Shika Yakuhin Co., Ltd., Shimonoseki, Japan) for 60 seconds
The color of the dentin blocks did not change after GO application (Figures 1B and 1C)

Summary

Introduction

Graphene oxide (GO) exhibits a monolayer sheet of carbon with a thickness of 1 nm or less, which partly contains sp hybridized carbon atoms and oxygen functional groups, such as epoxy, carboxy and hydroxy groups. Krishnamoorthy et al showed that GO exerted antibacterial activity against Pseudomonas aeruginosa and Streptococcus iniae [1]. Hu et al reported that oxidized graphene sheets showed antibacterial activities, the cytotoxicity of GO sheets was slight [3]. 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. 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

Results

Conclusion