Punica granatum: A plant with a high potential for the synthesis of silver nanoparticles

Objective: To use extracts of pomegranate as a reducing agent to the simple and eco-friendly biosynthesis of silver nanoparticles and their antimicrobial evaluation against different bacteria. Methods: The peel of the ripe fruits and leaves of pomegranate were used to prepare aqueous and methanolic extracts to synthesize silver nanoparticles (AgNP) these nanoparticles were evaluated by techniques used for the characterization of nanoparticles that allow defining their size, shape and quality of dispersion in aqueous media. They were characterized by UV-Vis spectroscopy and dynamic light scattering (DLS). The antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis y Staphylococcus aureus was determined. Results: UV-Vis spectra with absorption peaks at 425 nm were observed for the nanoparticles synthesized with aqueous extract as well as for the nanoparticles synthesized with the methanolic extract. Regarding the size distribution and dispersion in solution, the zeta potential shows that the surface charge in all cases is negative with an average value from -28.0 mV to -52.0 mV. About the size, smaller nanoparticles were obtained from the aqueous extracts of the peel and leaf with values between 1.42 - 2.96 nm and10 - 19.04 nm for nanoparticles from the methanolic extracts. Inhibition of microorganisms by nanoparticles showed better inhibition against Escherichia coli with a MIC of 0.83 µg/mL up to 6.68 µg/mL. Conclusions: This study suggest that pomegranate extracts synthesize small-sized, well-dispersed nanoparticles with almost spherical morphology, with good antimicrobial activity against gram-negative bacteria such as Escherichia coli.O Objective: To use pomegranate (Punica granatum L.) extracts as a reducing agent for a simple and eco-friendly biosynthesis of silver nanoparticles and to test the latter’s antimicrobial potential against different bacteria. Methodology: The leaves and peel of ripe fruits of pomegranate were used to prepare aqueous and methanolic extracts to synthesize silver nanoparticles (AgNP). Then we evaluated these nanoparticles with techniques that allowed us to define their size, shape, and dispersion quality in aqueous media. To characterize the AgNPs we resorted to UV-Vis spectroscopy and dynamic light scattering (DLS). We determined their antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. Results: UV-Vis spectra were observed with absorption peaks at 425 nm for the nanoparticles synthesized with both aqueous and methanolic extracts. Regarding size, distribution, and dispersion in solution, the zeta potential shows that the surface charge in all cases is negative, with an average value ranging from -28.0 mV to -52.0 mV. Smaller nanoparticles were obtained from the aqueous extracts of the peel and leaves, with values between 1.42 - 2.96 nm, while the methanolic extracts yielded nanoparticles of 10 - 19.04 nm. Inhibition of microorganisms proved to be best against Escherichia coli, with a minimum inhibitory concentration (MIC) of 0.83 µg/mL up to 6.68 µg/mL. Conclusions: This study suggests that pomegranate extracts synthesize small-sized, well-dispersed silver nanoparticles with an almost spherical morphology, and good antimicrobial activity against gram-negative bacteria such as Escherichia coli

Application of Silver Nanoparticles to Improve the Antibacterial Activity of Orthodontic Adhesives: An In Vitro Study

There is a significant change in the bacterial plaque populations in the oral cavity during and after orthodontic treatment. Numerous studies have demonstrated that 2–96% of patients could increase the risk of white spot lesions. Streptococcus mutans and Lactobacilli ssp. are responsible for these white spot lesions. In this work, silver nanoparticles (AgNPs) with a diameter of 11 nm and dispersed in water were impregnated onto three different commercial orthodontic adhesives at 535 μg/mL. The shear bond strength (SBS) was assessed on 180 human premolars and metallic brackets. The premolars were divided into six groups (three groups for the commercial adhesives and three groups for the adhesives with AgNPs). All the groups were tested for their bactericidal properties, and their MIC, MBC, and agar template diffusion assays were measured. After adding AgNPs, the SBS was not significantly modified for any adhesive (p > 0.05), and the forces measured during the SBS did not exceed the threshold of 6 to 8 MPa for clinical acceptability in all groups. An increase in the bactericidal properties against both S. mutans and L. acidophilus was measured when the adhesives were supplemented with AgNPs. It was concluded that AgNPs can be supplement commercial orthodontic adhesives without modifying their mechanical properties with improved bactericidal activity