Quaternary Ammonium Carbon Dots with High Positive Charge and Biocompatibility: An Efficient Nano-Antimicrobial for Accelerating Bacteria-Infected Wound Healing

To overcome the limitations of traditional quaternary ammonium compounds (QACs) (environmental sensitivity, resistance induction, and poor biocompatibility), we developed antibacterial nitrogen-doped carbon dots (N-CDs) via a green dry-heat synthesis method using 2,3-epoxypropyltrimethylammonium chloride as a precursor. The process integrates carbonization and functionalization in a one-step approach, enabling precise control over the molecular structure to retain active quaternary ammonium groups. The N-CDs exhibit a unique dual bactericidal mechanism: surface positive charges disrupt bacterial membrane integrity via electrostatic interactions, while simultaneously inducing reactive oxygen species (ROS) bursts to trigger oxidative stress, synergistically enhancing bactericidal efficacy. The material demonstrates excellent biocompatibility (hemolysis rate < 5%, cell viability > 80%). In a Staphylococcus aureus (S. aureus)-infected mouse model, the N-CDs significantly accelerated wound closure rates, along with well-organized collagen deposition. Histopathology revealed intact organ structures with no infiltration of inflammation or pathological damage. Systemic biosafety was confirmed with biochemical indicators within normal thresholds. This study overcomes the key barriers of traditional QACs, providing a promising nanomaterial solution for drug-resistant bacterial infections, particularly in wound-healing biomaterials and antibacterial coatings for implantable medical devices.