The antibacterial effects of green synthesized silver nanoparticles by Achillea millefolium extract

Abstract: Today, nanotechnology has created a new perspective on all materials. In this perspective, by changing the size and type of particle placement, new properties can be obtained, causing their further application. In general, nanoparticles have tremendous properties created due to an increase in the surface-to-volume ratio of these materials. Antibacterial effects are not excluded from this rule, which means nanoparticles exhibit a different effect rather than the bulk materials. There are different methods for the synthesis of nanoparticles [1]. Chemical methods of nanoparticles synthesis, despite their extensive application, have provoked many environmental and human hazards [2]. Whereas the green synthesis method using plant extracts is one of the easiest, cheapest, affordable and most used methods. Furthermore, the most important advantage of green synthesis of nanomaterials is their environmental friendly nature [3]. Microbes cannot develop resistance to silver as they can to antibiotics. Therefore, silver and silver nanoparticles (Ag-NPs) are used as an antimicrobial in a diversity of industrial, healthcare, and domestic applications. For example, infusing clothing with Ag-NPs thus allows them to stay odorless for more time [4]. The present study reports a modern and rapid method for synthesis of Ag-NPs. we have used a green method for the synthesis of nanoparticles by Achillea millefoliume extract which acts as a capping agent. Achillea millefoliume is a flowering plant in the family Achillea (Asteraceae). Green synthesized Ag-NPs by the extract were characterized by using UV–visible spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS) and X-ray diffraction (XRD). Antibacterial effects of synthesized Ag-NPs were investigated by evaluating the bacterial inhibition zone and their minimum inhibitory concentration (MIC). The bacteria used in this study were from both Gram-positive (Staphylococcus aureus, Bacillus cereus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa). In the inhibition zone test, four concentrations (0.5, 1, 1.5 and 2 mM) of nanoparticles were investigated. The greatest inhibitory zone diameter was observed at 2 mM concentration of Ag-NPs. In addition to, zone test results showed that this effect is the same for both kind of bacteria. MIC results showed that the MIC of Ag-NPs for B. cereus and P. aeruginosa are 0.0125 mM, and for E. coli and S. aureus, are 0.025 mM.