Synthesis and Characterization of Silibinin-Loaded ZIF-8 Nanocomposites and Their Antibacterial Activity Against Escherichia coli: Insights into acrB, recA, and htpX Gene Expression

Abstract

Background/Objectives: In this study, ZIF-8 and silibinin-loaded ZIF-8 nanostructures containing different concentrations of silibinin were successfully synthesized using a one-pot method and characterized by FT-IR, SEM, and EDX analyses. Methods: The antibacterial activities of the synthesized nanostructures were subsequently evaluated against Escherichia coli, Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Results: Among all tested formulations, S2@ZIF-8 exhibited the strongest antibacterial activity against E. coli, with an MIC of 32 μg/mL and an MBC of 64 μg/mL. In the agar well diffusion assay, S2@ZIF-8 produced an inhibition zone of 12.1 ± 0.35 mm. The antibiofilm activity evaluated at the MIC revealed inhibition rates of 52.6 ± 0.50%, 33.5 ± 0.50%, and 29.9 ± 0.17% for S2@ZIF-8, S1@ZIF-8, and pristine ZIF-8, respectively. Furthermore, gene expression analysis demonstrated that S2@ZIF-8 exerted a marked inhibitory effect on acrB and htpX gene expression, while producing a comparatively moderate suppressive effect on recA. Conclusions: Overall, S2@ZIF-8 exhibited superior antibacterial and antibiofilm activity among the tested formulations.