Characterization of silver nanoparticles synthesized using Urtica dioica Linn. leaves and their synergistic effects with antibiotics

In continuation of the efforts for synthesizing silver nanoparticles (AgNPs) by green chemistry route, here we report a facile bottom-up ‘green’ route for the synthesis of AgNPs using aqueous leaves extract of Urtica dioica (Linn.). The synthesized AgNPs were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Zeta-sizer and Zeta-potential, Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) spectroscopy, Transmission electron microscopy (TEM) and Selected area electron diffraction (SAED). The results obtained from various characterizations revealed that AgNPs were in the size range of 20–30 nm and crystallized in face-centered-cubic structure. The antibacterial activity against Gram-positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Salmonella typhimurium) bacterial pathogens was demonstrated by synthesized nanoparticles. Further, synergistic effects of AgNPs with various antibiotics were evaluated against above mentioned bacterial pathogens. The results showed that AgNPs in combination with antibiotics have better antibacterial effect as compared with AgNPs alone and hence can be used in the treatment of infectious diseases caused by bacteria. The maximum effect, with a 17.8 fold increase in inhibition zone, was observed for amoxicillin with AgNPs against S. marcescens proving the synergistic role of AgNPs. Therefore, it may be used to augment the activities of antibiotics.