Green synthesis, characterization, antibacterial and biofilm inhibitory activity of silver nanoparticles compared to commercial silver nanoparticles

This study was aimed to fabricate Zataria multiflora-derived silver nanoparticles (AgNPs) and evaluate the antibacterial activity and biofilm inhibitory activity of plant-mediated fabricated AgNPs (P-AgNPs) compared to commercial AgNPs (C-AgNPs) against Staphylococcus aureus ATCC 25923. The P-AgNPs were characterized by using UV–vis spectroscopy, Transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersive X-ray spectroscopy (EDX), Dynamic Light Scattering (DLS), and Fourier Transform Infrared (FT-IR) spectrum. The P-AgNPs were formed fairly uniform in size with a spherical morphology and an average hydrodynamic diameter of 25.5 nm at pH value of 9. Besides, the EDX analysis confirmed the presence of silver ions in the fabricated P-AgNPs. The FT-IR analysis also confirmed the presence of different functional groups on the surface of P-AgNPs. The P-AgNPs and C-AgNPs represented significant antibacterial activity with minimum inhibitory concentration (MIC) of 4 and 8 µg/mL against S. aureus, respectively. Both P-AgNPs and C-AgNPs at the concentrations of 0.5, 1, 2, and 4*MIC caused strong biofilm, weak biofilm, weak biofilm and no biofilm, respectively. Notably, at the concentrations of ≥8 µg/mL, both types of AgNPs exhibited significant biofilm inhibitory activity, whereas at the lower concentrations, the P-AgNPs showed greater biofilm inhibition formed by S. aureus.