2,2-Diphenyl-1-Picrylhydrazyl Free Radical Scavenging Assay and Bacterial Toxicity of Protein Capped Silver Nanoparticles for Antioxidant and Antibacterial Applications

Abstract

Current study deals with the synthesis, in vitro antioxidant and bacterial toxicity of silver nanoparticles using aqueous extract of Senna siamea plant seed. The reaction mixture turned to brownish colour after 2 h of incubation and was confirmed by surface Plasmon spectra using UV-visible spectrophotometer around 440 nm characteristic of silver nanoparticles. The stability of silver nanoparticles is due to the high negative values of zeta potential and capping of phytoconstituents which is present in the aqueous extract of S. siamea seed which is evident from Fourier transform infrared spectroscopy studies. Dynamic light scattering (DLS) studies revealed that the diameter of stable silver nanoparticles was approximately 70 nm in size and -22.9 mV zeta potential value with high stability. High resolution transmission electron microscopy analysis showed that the silver nanoparticles were poly dispersed with spherical shape. X-Ray diffraction studies revealed that most of the nanoparticles were face centered cubic in shape. Synthesized silver nanoparticles showed effective antioxidant activity against to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Phytosynthesized silver nanoparticles showed potent antibacterial activity against two gram positive (Staphylococcus aureus and Bacillus subtilis) and three gram negative (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia) human pathogenic bacteria which leads towards the clinical use as antibacterial agent.