The non-toxic properties and inherent antibacterial power of carbon nanoparticles (CNPs) and their nanocomposites with other metal nanoparticles have attracted much attention in recent years. Moreover, the combination of CNPs with other nanoparticles has shown enhanced antibacterial effects, making them promising candidates for reducing resistance and improving targeted delivery. In this study, CNPs were produced by the hydrothermal method from the biomass of Vibrio sp. VLC. To increase the biological properties of this nanostructure, zinc oxide nanoparticles (ZnO NPs) were produced by the cell lysed extract (CLS) of Vibrio sp. VLC and doped on the surface of CNPs to form CNPs/ZnO nanocomposite. The morphology and characteristics of the produced nanostructures were evaluated by Uv-Vis, FTIR, XRD, DLS and FE-SEM-EDX methods. The results showed that the average size of CNPs and CNPs/ZnO nanocomposite were 23.31 and 37.62 nm, respectively, and both possessed quasi-spherical structures. The antimicrobial and anti-biofilm activity of CNPs and CNPs/ZnO nanocomposite on 4 MDR Escherichia coli isolates (E6, E22, E27 and E55) were investigated in the concentration range of 195.31-25000 µg/ml. The growth inhibition percentages (GI %) at a concentration of 25,000 μg/ml for CNPs and the CNPs/ZnO nanocomposite were calculated as follows: E6 (64% and 71.5%), E22 (76.5% and 86.7%), E27 (74.5% and 85.7%), and E55 (70.7% and 86%). Also, both nanostructures effectively inhibited biofilm formation of E. coli clinical isolates in a dose dependent manner, with the CNPs/ZnO nanocomposite demonstrating superior anti-biofilm activity. In this study, the use of bacteriogenic CNPs/ZnO nanocomposite as a new anti-biofilm and antimicrobial agent significantly reduced the growth of antibiotic-resistant and biofilm-producing clinical E.coli strains.

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