Low-Toxicity Antibacterial Carbon Nanodots for Wound Dressings and Food Packaging

Carbon nanodots (CDs) are known to inhibit the growth of bacteria, and a developing trend is observed in the literature that attributes such activities specifically to photoactivation, N-doping, and/or surface charge. In this study, we demonstrate that CDs can inhibit bacteria growth as well without these predispositions. Using the minimum inhibitory concentration and minimum bactericidal concentration protocols, we study, without irradiation, the inhibitory activities of CDs that are low in N-content and surface charge, against Escherichia coli O157:H7, Salmonella enterica ser. Typhimurium, and Staphylococcus aureus. The CDs are further tested in a zebrafish model for acute toxicity. These CDs exhibit antibacterial activities comparable to those of previously reported CDs with IC50s of 0.66, 0.75, and 1.00 mg/mL for the three bacteria, respectively. They are also shown to have manageable acute toxicity for safe applications in areas such as antibacterial wound dressing and food packaging. These results indicate that our knowledge base of the required characteristics for CDs to be antibacterial is incomprehensive despite the burgeoning of studies in this area, and the biological pathways leading to such activities are much more diverse than the current literature has suggested.