The extra cellular synthesis of gold and silver nanoparticles and their free radical scavenging and antibacterial properties

Abstract

The bio reduction of chloro auric acid (HAuCl4) and silver nitrate (AgNO3) is achieved extracellularly by using the aqueous extract of Solanum torvum (S. torvum) fruit. The nanoparticle formation was screened by UV–visible spectroscopy through color conversion due to surface plasma resonance bands at 560nm and 430nm for gold and silver nanoparticles respectively. The spherical shapes with smooth surface of gold and silver nanoparticles were analyzed through scanning electron microscope and its presence was confirmed by energy dispersive X-ray spectroscopy (SEM/EDX). The functional groups in the gold and silver salts and the bio interactive functional groups present in the S. torvum extract were characterized by employing Fourier transform infra-red spectroscopy (FTIR). The biomedical properties of gold and silver nanoparticles were premeditated as free radical scavenging activity and antibacterial static agents. Gold and silver nanoparticles serve as strong hydroxyl, superoxide, nitric oxide and DPPH radical scavengers in contrast to their corresponding metal oxides. The radical quenching properties of gold and silver nanoparticles were found to correlate with in vitro DNA protective effect. The silver nanoparticles show strong zone of inhibition against Escherichia coli, Pseudomonas and Bacillus whereas, gold nanoparticles exhibit fair zone of inhibition. To our knowledge this is the first report that S. torvum extract can reduce metal acids to nano materials.