Antibacterial mechanism analysis and structural design of amino acid-based carbon dots

摘要

Carbon dots have attracted much attention in the field of antibacterial because of their good biocompatibility, easy preparation, and basically not inducing bacterial resistance. At present, studies have shown that many antibacterial carbon dots have high positive surface potential, but few researchers have been carried out on how to design carbon dots with high positive surface potential by using nontoxic precursors. In this paper, three structurally similar amino acids with different isoelectric points were selected as carbon sources, and three kinds of carbon dots based on amino acid were synthesized with hydrothermal method. The structural characteristics of the three carbon dots were characterized by XRD, FT-IR, XPS, etc. The content of nitrogen-containing groups of the three carbon dots was compared with the Kaiser test. The relationship between the Zeta potential and the antibacterial effect was also investigated. And it shows that the arginine carbon dots, which have the highest positive charge, also have the best antibacterial performance. So, the arginine carbon dots were further doped with nitrogen-containing molecules (diethylenetriamine, DETA) to obtain high surface positive potential carbon dots (named DETA-Arg-CDs, Zeta potential = + 21.7 mV) with the minimum inhibitory concentration (MIC) against E. coli and S. aureus being 8 and 4 ug/mL, respectively. The antibacterial mechanism of high surface positive potential carbon dots was demonstrated by a series of experiments and computational simulations. Cytotoxicity tests showed that the carbon dots were almost nontoxic within the range of antibacterial concentration. Finally, it was applied to the preparation of antibacterial masks. The bacteriostatic zone experiment showed that the mask sprayed with DETA-Arg-CDs had an obvious bacteriostatic zone, while the blank control group had no bacteriostatic zone. In summary, this study synthesized carbon dots with excellent antibacterial properties by using simple and safe amino acids and small nitrogen-containing molecules and explored the antibacterial mechanism of carbon dots with high surface positive charge.