Application of Amino Acid-Based Carbon Dots for the Treatment of Oral Bacteria and Oral Cancer Cells In Vitro Using a Dental Light-Curing Unit via ROS-Mediated Therapy

In systemic diseases, controlling oral bacteria and cancer is an important issue. As biomaterials, recently, carbon dots (DSs) are the focus of a variety of studies owing to their extensive applicability in life sciences. In this study, the effectiveness of carbon dots (CDs) for the elimination of both oral bacteria and oral cancer in vitro was assessed using a dental light-curing unit (LCU) as a light source. CDs were synthesized using an amino acid. The absorbance of CDs and the emission spectrum of the LCU were measured. The production of reactive oxygen species (ROS) was evaluated spectroscopically. Changes in glutathione (GSH) content were evaluated. Using oral bacteria and cancer cells, in vitro antibacterial and antitumor capabilities of CDs were evaluated under light irradiation. Confocal microscopy was used to observe live/dead cells and intracellular lipid peroxidation (LPO). The emission spectrum of the LCU fully matched the absorbance of CDs. After CD treatment, the initial peak absorbances of the p-nitrosodimethylaniline-imidazole (for singlet oxygen assay) and nitroblue tetrazolium (for superoxide oxide assay) solutions changed under light irradiation. The initial peak absorbance of the GSH assay solution decreased during and after light irradiation. Both CD-treated oral bacteria and oral cancer cells were near totally eliminated at 50 and 200 μg/mL concentrations, respectively, after light irradiation. In the live/dead cell and C11-BODIPY^581/591 dye assays, red and green fluorescent spots were, respectively, observed in the CD-treated and light-irradiated cells. Accordingly, CDs effectively eliminated both oral bacteria and cancer cells in vitro in conjunction with dental LCU with less damage to normal cells through ROS-induced or ROS-initiated GSH depletion-induced intracellular LPO. Dental LCU plays a crucial role in ROS production through CD photoexcitation. Dental LUC has the potential to be used as a light source in dentistry for the treatment of oral bacteria and cancer cells.