Photo-sensitive Antibacterial Activity of o-Phenylenediamine Carbon Dots

Carbon dots (CDs) are among the famous nanoparticles that have been widely developed due to high biocompatibility, low toxicity, ease of preparation, excellent photoluminescent properties, and outstanding application in biomedicine. Among the various biomedical activities of CDs, they can be applied as antibacterial agents because of their photodynamic properties. Photodynamic therapy (PDT) has been considered an alternative antibacterial agent because of its non-invasive nature and minimal side effects, especially in terms of improving antibacterial activity against multidrug resistant bacteria when compared with traditional antibiotics. In this research, we developed CDs from o-phenylenediamine (OP). The o-phenylenediamine CDs (OPCDs) were synthesized via a hydrothermal method at 180°C for 3 h. After that, they revealed a spherical shape with a size range of 16.38 ± 2.64 nm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of OPCDs against Staphylococcus aureus (S. aureus) for both light exposure and without light exposure groups were significantly greater than the OP solution because the OPCDs could generate reactive oxygen species (ROS) via a photodynamic mechanism leading to the bacteria cell death. Therefore, the created OPCDs may have the capability to be utilized for treating skin infections caused mainly by S. aureus. In conclusion, OPCDs could be proposed as nanomaterials that enhance antibacterial activity and provide photodynamic properties.