Natural biomass-derived carbon dots as potent antimicrobial agents against multidrug-resistant bacteria and their biofilms

Abstract

Infections caused by multidrug-resistant (MDR) bacteria have become a major challenge for healthcare systems worldwide. Antibacterial carbon dots (CDs) have received increasing attention for fighting MDR bacteria. In this study, we synthesized nitrogen and sulfur self-doped garlic carbon dots (GCDs) via a one-step hydrothermal method. The prepared GCDs are sphere-like nanoparticles with graphite lattice structure and positive charge (+8.53 mV). The minimum inhibitory concentrations (MICs) of GCDs against methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Salmonella Typhimurium (MRST), and generic Escherichia coli were 25 μg/mL, 75 μg/mL, and 50 μg/mL, respectively. The MICs of kanamycin against MRSA and MRST were approximately 64 and 18 times higher than those of GCDs, respectively. GCDs at 200 μg/mL eliminated all three bacteria within 180 min. GCDs also effectively inhibited the biofilm formation of MRSA and MRST in a dose-dependent manner. The antimicrobial mechanisms of GCDs against MDR bacteria include: (1) electrostatic interaction facilitated penetration into MDR bacteria; (2) disruption of cell structure and subsequent leakage of intracellular components; (3) induction of oxidative stress and inhibition of the antioxidant enzymes. In addition, GCDs showed high biocompatibility in hemolysis assays and vitro cytotoxicity assays. In conclusion, this study developed a novel antimicrobial nanomaterial based on natural plants, providing an important idea for the rational use of natural biomass against MDR bacterial infections.