Nitrogen-doped carbon dots for combating bacterial infections via synergistic membrane disruption and biofilm eradication

Nitrogen-doped carbon dots (N-CDs) have emerged as promising antibacterial nanomaterials. In this work, a series of N-CDs with varying nitrogen doping levels (0%–20%) were synthesized via a one-step hydrothermal method using D-sorbitol and L-lysine as precursors, targeting the growing challenge of bacterial infections. The resulting samples were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy, ultraviolet–visible (UV-Vis) absorption and fluorescence spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Zeta potential/particle size analysis. The effects of nitrogen doping on the structural, optical, physicochemical, and antibacterial properties were systematically investigated. The 15% N-CDs exhibited optimal antibacterial activity against Escherichia coli ( E. coli) and Staphylococcus aureus ( S. aureus ), with inhibition rates of 95.32% ± 1.41% and 91.61% ± 1.36%, respectively, while showing excellent biocompatibility toward normal mammalian cells (HUVEC and HT-22) up to 700 μM. Mechanistic studies revealed that the optimal 15% N-CDs adhere to bacterial surfaces, disrupt cell membrane integrity, and inhibit biofilm formation (up to 81.1% ± 0.13% and 76.94% ± 0.24%), as evidenced by SEM, live/dead staining, and leakage assays. Collectively, these findings establish N-CDs as a promising nanoplatform that tackles bacterial infections through a synergistic membrane-damaging and biofilm-suppressing mechanism, without compromising mammalian cell viability.