title: Study of mechanism of enhanced antibacterial activity by green synthesis of silver nanoparticles.
abstract: The extensive use of silver nanoparticles needs a synthesis process that is greener without compromising their properties. The present study describes a novel green synthesis of silver nanoparticles using Guava (Psidium guajava) leaf extract. In order to compare with the conventionally synthesized ones, we also prepared Ag-NPs by chemical reduction. Their optical and morphological characteristics were thoroughly investigated and tested for their antibacterial properties on Escherichia coli. The green synthesized silver nanoparticles showed better antibacterial properties than their chemical counterparts even though there was not much difference between their morphologies. Fourier transform infrared (FTIR) spectroscopic analysis of the used extract and as-synthesized silver nanoparticles suggests the possible reduction of Ag(+) by the water-soluble ingredients of the guava leaf like tannins, eugenol and flavonoids. The possible reaction mechanism for the reduction of Ag(+) has been proposed and discussed. The time-dependent electron micrographs and the simulation studies indicated that a physical interaction between the silver nanoparticles and the bacterial cell membrane may be responsible for this effect. Based on the findings, it seems very reasonable to believe that this greener way of synthesizing silver nanoparticles is not just an environmentally viable technique but it also opens up scope to improve their antibacterial properties.
authors.affiliation: Department of Physics, Banaras Hindu University, Varanasi, India.
authors.forename: Upendra Kumar
authors.initials: UK
authors.lastname: Parashar
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
authors.forename: Tanmay
authors.initials: T
authors.lastname: Bera
authors.forename: Preeti S
authors.initials: PS
authors.lastname: Saxena
authors.forename: Gopal
authors.initials: G
authors.lastname: Nath
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Srivastava
authors.forename: Rajiv
authors.initials: R
authors.lastname: Giri
authors.forename: Anchal
authors.initials: A
authors.lastname: Srivastava
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000188:drug therapy; D055772:Green Chemistry Technology / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D031647:Psidium / Q000737:chemistry; D012834:Silver / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D012834:Silver