The exceptional properties of the silver nanoparticles offer several applications in the biomedicine field. The development of antibiotics which are clinically useful against bacteria and drug resistant microorganisms, it is one of the main approaches of silver nanoparticles. However, it is necessary to develop environmentally friendly methods for their synthesis. In this sense, the main objective of this work is focused on to propose a simplified and efficient green synthesis of silver nanoparticles with proven antibacterial properties. The green synthesis route is based on the use of the Melissa officinalis as reducing agent of the silver ions in aqueous solution at room temperature. Complementary, the antibacterial activity of the silver nanoparticles against Staphylococcus aureus and Escherichia coli was confirmed. The silver nanoparticles obtained were characterized by transmission electron microscopy, X-ray diffraction, UVâvis, Raman and FT-IR spectroscopy. The observed results suggested that using Melissa officinalis, it is possible to performed silver nanoparticles with controlled characteristics and with significant inhibitory activity against the Staphylococcus aureus and Escherichia coli. Keywords: Green synthesis, Nanoparticles, Antibacterial effec

The adhesion ability and adaptability of bacteria, coupled with constant use of the same bactericides, have made the increase in the diversity of treatments against infections necessary. Nanotechnology has played an important role in the search for new ways to prevent and treat infections, including the use of metallic nanoparticles with antibacterial properties. In this study, we worked on the design of a composite of silver nanoparticles (AgNPS) embedded in poly-epsilon-caprolactone nanofibers and evaluated its antimicrobial properties against various Gram-positive and Gram-negative microorganisms associated with drug-resistant infections. Polycaprolactone-silver composites (PCL-AgNPs) were prepared in two steps. The first step consisted in the reduction in situ of Ag⁺ions using N,N-dimethylformamide (DMF) in tetrahydrofuran (THF) solution, and the second step involved the simple addition of polycaprolactone before electrospinning process. Antibacterial activity of PCL-AgNPs nanofibers againstE. coli,S. mutans,K. pneumoniae,S. aureus,P. aeruginosa, andB. subtiliswas evaluated. Results showed sensibility ofE. coli,K. pneumoniae,S. aureus, andP. aeruginosa, but not forB. subtilisandS. mutans. This antimicrobial activity of PCL-AgNPs showed significant positive correlations associated with the dose-dependent effect. The antibacterial property of the PCL/Ag nanofibers might have high potential medical applications in drug-resistant infections.

Antibiotic resistance by bacteria has continued to prompt research for new agents that can inhibit bacterial growth. Therefore, in this study, we described the synthesis, physicochemical characterization, and the antibacterial activity of pure metal oxide nanoparticles of ZrO₂ and ZnO and the antibacterial activity of their mixed metal oxide of ZrO₂–ZnO nanoparticles against three Gram-positive of Bacillus subtilis, Streptococcus mutans, Staphylococcus aureus, and 3 Gram-negative of Escherichia coli, Pseudomonas aeruginosa, and Klebsiella oxytoca. The nanoparticles were successfully prepared by sol–gel method and were subsequently characterized using dynamic light scattering analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results obtained from the characterization techniques confirm the formation of ZrO₂, ZnO, and ZrO₂–ZnO nanoparticles with diameter sizes of 76, 22, and 26–34 nm, respectively. SEM reveals spherically shaped nanoparticles. The XRD shows the formation of monoclinic zirconia and hexagonal zinc oxide, formation of amorphous compound in Z-Z_0.25 and Z-Z_0.5 while Z-Z_1.0 and Z-Z_2.0 have peaks that corresponds to the diffractogram pattern present in ZrO₂ and ZnO. From the preliminary screening, ZrO₂ and the amorphous particles of Z-Z_0.25 and Z-Z_0.5 did not record any inhibition against any of the test bacteria while ZnO, Z-Z_1.0, and Z-Z_2.0 recorded inhibition against all the tested bacteria.