Greener approach for synthesis of antibacterial silver nanoparticles using aqueous solution of neem gum (Azadirachta indica L.)

•First report on autoclave assisted green synthesis of AgNPs using neem gum.•Carbonyl, hydroxyl and amino group of gum stabilize AgNPs.•Monodispersed-spherical shaped AgNPs found to be <30 nm.•Antibacterial mechanism of AgNPs was also proposed.

A simple method for the green synthesis of silver nanoparticles (AgNPs) using autoclave assisted gum extract of neem (Azadirachta indica) has been investigated for the first time. Silver nanoparticles were formed due to reduction of silver nitrate solution when mixed with the gum extract after autoclaving at 121 °C and 15 psi. The UV–vis absorption spectrum of the biologically reduced reaction mixture showed the surface plasmon peak at 418 nm which is characteristic peak of silver nanoparticles. The functional biomolecules present in the gum extract and the interaction between the nanoparticles were identified by the Fourier transform infrared spectroscopy (FTIR) analysis. Average diameter of the synthesized nanoparticles was found to be <30 nm, as revealed from transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis. X-ray diffraction (XRD) analysis confirmed the face-centered cubic crystalline structure of metallic silver. The synthesized silver nanoparticles exhibited antibacterial activity against clinical isolates of Salmonella enteritidis and Bacillus cereus. Moreover, the antibacterial activity of the silver nanoparticles was further confirmed by degradation of test bacterial DNA. The results suggest that the gum mediated synthesized silver nanoparticles could be used as a promising antibacterial agent against clinical pathogens.

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