Trachyspermum copticum aqueous seed extract-derived silver nanoparticles: Exploration of their structural characterization and comparative antibacterial performance against gram-positive and gram-negative bacteria

Abstract

Abstract In this study, the aqueous seed extract of Trachyspermum copticum was employed to fabricate silver nanoparticles (AgNPs) for their antibacterial performance. The structural characteristics of the phytofabricated AgNPs were investigated using ultraviolet–visible, energy dispersive X-ray, dynamic light scattering, zeta potential, field emission scanning electron microscope, and Fourier transform infrared spectroscopy. Further, the antibacterial effects of AgNPs were evaluated against two standard gram-positive strains of Staphylococcus aureus and Streptococcus pyogenes and two standard gram-negative strains of Escherichia coli and Klebsiella pneumoniae. The findings showed the phytofabrication of spherical-shaped AgNPs with a Z-average diameter of 119.7 nm and the polydispersity index of 0.56. The minimum inhibitory concentration of AgNPs against S. aureus, S. pyogenes, E. coli, and K. pneumoniae strains was 0.25, 1, 0.5, and 0.5 μg·mL−1, respectively. In addition, the minimum bactericidal concentration of these nanoparticles (NPs) against the mentioned strains was 8, 16, 4, and 4 μg·mL−1, respectively. Furthermore, the AgNPs enhanced the generation of reactive oxygen species significantly in all studied bacteria compared to the control (P < 0.05) suggesting an oxidative-associated antibacterial mechanism of AgNPs. Moreover, a dose-dependent cell death was found in all bacterial samples based on flow cytometry analysis. Overall, this study showed a biological approach for the biosynthesis of AgNPs with significant antibacterial effects.