Couroupita guianensis leaf callus extract mediated synthesis and antibacterial activity of silver nanoparticles

Abstract

Objectives: Synthesis and evaluation of antimicrobial potential of silver nanoparticles (AgNPs) using aqueous leaf callus extract of Couroupita guianensis. Methods: AgNPs were fabricated by green synthesis method using an aqueous extract of callus as agent of reduction and stabilization. AgNPs formation and their elemental nature were confirmed by ultraviolet (UV)-absorption spectroscopy and energy dispersive X-ray spectroscopy, respectively. Morphology of AgNPs was characterized by scanning electron microscope and atomic force microscope. Functional groups of biomolecules associated with AgNPs were inferred from characteristic Fourier transform infrared spectroscopy (FTIR) peaks. Antimicrobial activity of the AgNPs was assessed on MTCC strains by Kirby-Bauer disc diffusion method. Result: Synthesized AgNPs exhibited characteristic UV/VIS absorption spectrum peaks at 410 nm. The sizes of metallic spherical nanoparticles ranged from 30.38 nm to 88.32 nm and were in small aggregates. FTIR spectroscopy peaks of AgNPs, 3268, 1603, 1395, 1319, and 1045 nm corresponds to carbons of hydroxyl, amines, and ethers groups. Antimicrobial activity of AgNPs against tested Gram-positive and negative bacterial strains is significant compared to silver ions and gentamicin, and the zone of inhibition ranged from 16±0.8mm to 20±0.1mm. Conclusions: Stable AgNPs were synthesized through reduction and capping of silver ions by polyphenols and proteins present in callus extract. The enhanced antimicrobial activity of AgNPs may due to their small size leading to efficient molecular contact with the cell surface, penetration, and interaction, and inactivation of vital biomolecules.