A comprehensive study of the antibacterial (bacteriostatic and bactericidal) properties of non-doped carbon nanodots (CNDs), nitrogen-doped (N-doped), and nitrogen/sulfur co-doped (N,S-doped) CNDs against Escherichia coli (a model organism) is discussed herein. The CNDs, with a size of ca. 5 nm, were found to be capable of inhibiting the growth of the bacterial biofilm but not significantly the growth of planktonic bacteria. Heteroatom doping was found to considerably improve the potential of CNDs as bactericidal agents. Further experiments were conducted to shed light on the potential mechanism of the antibacterial activity of the CNDs. The results showed that the CNDs do not interact with the cellular membrane via electrostatic forces. Following a simple metabolomic workflow, no alterations of the bacterial metabolome were observed except for the activation of the metabolism of α-linolenic acid. The CNDs neither oxidize cell membrane lipids and intracellular proteins nor elevate the concentration of reactive oxygen species in cells. Finally, the interactions of CNDs with genomic DNA and RNA revealed that CNDs are able to intercalate into their structure. The different affinities of the three kinds of CNDs for DNA/RNA account for the differences in their antibacterial activity and constitute the main mechanism via which CND activity is achieved.

Graphical abstract

全面研究了非掺杂碳纳米点（CND），氮掺杂（N掺杂）和氮/硫共掺杂（N，S掺杂）CND对大肠杆菌的抗菌（抑菌和杀菌）性能。（模型生物）在本文中讨论。大小约为CN的CND。发现5nm的波长能够抑制细菌生物膜的生长，但是不能显着抑制浮游细菌的生长。发现杂原子掺杂显着提高了CND作为杀菌剂的潜力。进行了进一步的实验以阐明CND抗菌活性的潜在机制。结果表明，CND不通过静电力与细胞膜相互作用。按照简单的代谢组学流程，除激活α-亚麻酸的代谢外，未观察到细菌代谢组的改变。CND既不氧化细胞膜脂质和细胞内蛋白质，也不提高细胞中活性氧的浓度。最后，CND与基因组DNA和RNA的相互作用揭示了CND能够插入其结构。三种CND对DNA / RNA的亲和力不同，这说明它们的抗菌活性不同，并构成了实现CND活性的主要机制。

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