Synergistic actions of phytonutrient capped nanosilver as a novel broad-spectrum antimicrobial agent: unveiling the antibacterial effectiveness and bactericidal mechanism

Nanosilver is a versatile biomedical agent that can potentially battle against bacterial infection. Herein, we introduce an energy-efficient green approach to synthesize phytonutrient modified silver nanoparticles (AgNPs) using the cogon grass extract (CGE) in 15 minutes. The biogenic AgNPs were characterized using UV-Vis, FT-IR, TEM, XRD, XPS, and zeta-potential measurements. The results from in vitro biological assays indicated that CGE-mediated AgNPs possess good antioxidant activity, broad-spectrum antibacterial activity, satisfactory dispersion stability, and trivial hemolytic activity. Among the reported biogenic AgNP studies, AgNPs synthesized using the CGE displayed a superior antibacterial performance against two drug-resistant Acinetobacter baumannii strains and showed stronger bactericidal capability toward E. coli and S. aureus. Investigation of the antibacterial mechanism of CGE-mediated AgNPs toward bacteria indicated the accumulation of AgNPs in the bacterial cells, steady release of silver ions, and production of reactive oxygen species to damage the bacterial surface structure. Additionally, our mass spectrometric screening revealed that several putative phytochemicals in the CGE act as the reducing agent capping on the AgNP surfaces, which intensifies the antibacterial activity. These data indicate that the CGE-mediated AgNPs can act as a broad-spectrum antibacterial agent in public health.