Bio‐fabrication of Silver Nanoparticles Using Alysicarpus vaginalis Extract: Preparation, Characterization and Comparative in vitro Antibacterial Evaluations

Abstract

AbstractGreen synthesis of silver nanoparticles (AgNPs) using the Alysicarpus vaginalis alcoholic extract as a reducing agent and a capping ligand was carried out. Notable peaks of λmax 442–602 nm indicated the reduction of silver ions to elemental AgNPs. Particle size (Zavg) was in the range of 32.3±0.76 to 252.3±0.342 nm). The negative Zeta potential (ZP, −2.9±0.31 to −21.7±0.13 mV) and low polydispersity index (PDI, 0.181±0.02 to 0.635±0.02) supported the homogeneous nature of AgNPs. Further, crystalline spherical nature of AgNPs with a smooth surface was confirmed by high‐resolution transmission electron microscopy (HRTEM) studies. The AgNPs showed 1.2 to 1.4‐fold enhanced antibacterial activity than extract (6–10 mm zone of inhibition) against Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, and Salmonella enterica ser. Typhi by disc diffusion assay. The AgNP formulation F9 showed equal (against Gram‐positive L. monocytogenes) or even better (against Gram‐negative S. enterica Typhi) antimicrobial activity than the positive control, ciprofloxacin. Further investigations on F9 are suggested in order to develop a broad‐spectrum, cost‐effective antibacterial formulation of natural origin. This study represents a significant step forward in the field of bio‐fabrication and presents a promising alternative to traditional chemical synthesis methods for the production of antimicrobial AgNPs.