ABSTRACT
Objective: To develop a novel method to synthesize silver nanoparticles (AgNPs) by using the extract of Yinqiao Jiedu Mixture waste, evaluate the effects of biosynthesis parameters on the formation and polydispersity of AgNPs, and investigate the antioxidative and antibacterial activity. Methods: The formation of AgNPs was confirmed by UV-visible spectroscopy; The size, polydispersity, surface and morphology features of AgNPs were characterized by laser granularity analyzer and transmission electron microscopy; The antioxidative and antibacterial activities of AgNPs were evaluated by calculating the scavenging rate for DPPH and A600 for both Escherichia coli and Staphylococcus aureus, respectively. Results: By using Yinqiao Jiedu Mixture waste, the AgNPs could be prepared at ambient temperature. The size and polydispersity index of the synthesized AgNPs were sensitive to the biosynthesis parameters, such as pH of extract and material proportion with the average size distribution was 14.2-94.8 nm, offering a size-controlled synthetic method for AgNPs. And when the pH was 6.0, the polydispersity could reach the best. The AgNPs could be obtained with high yield and small size at pH 10.0, material proportion 3:1 after reacting 2 h, which were quasi-spherical in shape with average size of (24.0 ± 0.3) nm and covered by anion [Zeta potential: (-23.1 ± 0.2) mV]. The synthesized AgNPs also revealed significant inhibition activities for the growth of E. coli and S. aureus with MIC 50.0 and 25.0 μg/mL, respectively, and potent antioxidative activity with scavenging rate for DPPH 71.1% when adding 100 μg/mL of AgNPs. Conclusion: The extract of Yinqiao Jiedu Mixture waste can be used to synthesize AgNPs with small size at ambient temperature; The biosynthesis parameters have significant effects on the average size and polydispersity index of AgNPs; The synthesized AgNPs have potent antioxidative and antibacterial activity.
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.
