Biological Synthesis of Silver Nanoparticles and Assessment of Their Bactericidal Activity
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abstract
Synthesis of silver nanoparticles (AgNPs) was carried out by a simple green method using extracts of two brown algal species (Sargassum sp. and Turbinaria sp.) as reducing agents for the first time. The effect of duration of the extraction of the algal species from the respective biomass was studied in water at 110 C over a range of 5 s to 5 min to achieve a maximum yield of bioactive components that can reduce silver ions. In addition, the effects of the concentration of algal extracts and pH (2.0 - 9.0) were investigated to identify optimum experimental conditions for the effective synthesis of AgNPs. The synthesized AgNPs were characterized using UVVis, TEM, and XRD techniques. The optimal experimental conditions for the effective biological synthesis of AgNPs included an extraction time of 30 s at pH 9.0. This finding was supported by the results of radical scavenging of the aqueous extracts, which were also high at the same extraction time. Phenolic contents of the extracts appeared to be the main reductants for the conversion of Ag(I) to Ag(0). The antibacterial activity of synthesized AgNPs was examined using four opportunistic pathogens (Klebsiella pneumonia, Aeromonas hydrophila, Pseudomonas aeruginosa, and Escherichia coli). In the present study, as low as 50 mg/L of AgNPs was found to inhibit all the four bacterial strains studied. The results demonstrated the effectiveness of synthesized AgNPs as the antibacterial agent.
