N-doped carbon dots derived from leaves with low toxicity via damaging cytomembrane for broad-spectrum antibacterial activity

Bacterial infection is one of the most serious health hazards for people all over the world. Simultaneously, with the wide application of antibiotics, drug-resistance has become a crucial issue. Numerous nanomaterials have been studied to fight bacteria. Yet few studies point out the relationship between carbon dots (CDs) from leaves and bacteria. In this work, three kinds of N-doped CDs by one-step hydrothermal method were synthesized from osmanthus leaves, tea leaves and milk vetch, respectively, and presented different broad-spectrum antibacterial activities via stemming from the damage of the cytomembrane. Among them, at maximum inhibitory concentration of 1000 mu g/mL, CDs from osmanthus leaves (OCDs) show the best antibacterial activity and only 13.09% of the E. coli and 3.37% S. aureus were alive. It is worth noting that so high concentration of OCDs owns low toxicity to cells. In contrast, CDs from milk vetch (MCDs) exhibit the worst antibacterial activity and even 70% of both species survived at the same concentration. This difference of antibacterial activity among the three CDs should put down to their diverse natural-occurring substance. This work provides a new perspective on the selectivity of low-toxicity and high-concentration carbon-based nanomaterials for broad-spectrum antibacterial materials.