Study of mechanism of enhanced antibacterial activity by green synthesis of silvernanoparticles

Abstract

The extensive use of silver nanoparticles needs a synthesis process that is greener withoutcompromising their properties. The present study describes a novel green synthesisof silver nanoparticles using Guava (Psidium guajava) leaf extract. In order tocompare with the conventionally synthesized ones, we also prepared Ag-NPs bychemical reduction. Their optical and morphological characteristics were thoroughlyinvestigated and tested for their antibacterial properties on Escherichia coli. The greensynthesized silver nanoparticles showed better antibacterial properties than theirchemical counterparts even though there was not much difference between theirmorphologies. Fourier transform infrared (FTIR) spectroscopic analysis of the usedextract and as-synthesized silver nanoparticles suggests the possible reduction ofAg + by the water-soluble ingredients of the guava leaf like tannins, eugenoland flavonoids. The possible reaction mechanism for the reduction ofAg + has been proposed and discussed. The time-dependent electron micrographs and thesimulation studies indicated that a physical interaction between the silver nanoparticlesand the bacterial cell membrane may be responsible for this effect. Based on the findings, itseems very reasonable to believe that this greener way of synthesizing silver nanoparticles isnot just an environmentally viable technique but it also opens up scope to improve theirantibacterial properties.