Synthesis and antibacterial activity of silver nanoparticles synthesized by Cornus officinalis aqueous extract / 中草药

ABSTRACT

Objective To develope a novel method to generate silver nanoparticles (AgNPs) in a mild condition by using the Cornus officinalis aqueous extract, study their antibacterial activity, and explore the mechanism of reduction reaction. Methods The formation of AgNPs was confirmed by UV-visible spectroscopy; The particle size, surface properties, and morphology features of AgNPs were characterized by laser particle analyzer as well as transmission electron microscopy; The mechanism of reduction reaction was studied by IR. The antibacterial activity of AgNPs was investigated by disk agar diffusion method. Results The AgNPs were prepared under mild reaction conditions by C. officinalis aqueous extract, the optimum condition is ultrasonic reaction for 4 h (pH 9.0). Quasi-spherical shaped AgNPs were synthesized with average particle size of 58.73 nm, which was uniform, stable, and well dispersed. The presence of flavonoids in C. officinalis aqueous extract may be the reductant to produce the AgNPs. In the meantime, the active components in the aqueous extract form a protective layer on the surface of AgNPs to prevent aggregation and increase the stability of AgNPs. Compared with the chemically synthesized AgNPs, the antibacterial activity of AgNPs generated by C. officinalis aqueous extract increased 20-fold and 40-fold for Escherichia coli and Staphylococcus aureus, respectively. Conclusion C. officinalis aqueous extract can prepare AgNPs under mild conditions, the flavonoids in the extract may be the reductive reagent and can stabilize AgNPs. The AgNPs prepared by this method have stronger antibacterial properties than those prepared by chemical method. The AgNPs synthesized by this method are stable and can be used as a new antimicrobial agent.