Indian Journal of Science and Technology

Abstract

Objective: Medicinal plant mediated green synthesis and the antimicrobiological application and assessment of the synthesized silver nanoparticles (AgNPs) constituted the objectives of this study. Lately, due to the emphasis on the green eco-friendly approach of the synthesis of AgNPs, aqueous extract of the aerial parts of Euphorbia geniculata was utilized to construct silver nanoparticles. Methods: Reduction of Ag+ ion to silver atom was rapid within minutes under direct sunlight, resulting in high yield of AgNPs. The synthesized silver nanoparticles were characterized by ultraviolet-visible (UV-vis.), Fourier transform-infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis. UV-vis. spectrum of the aqueous solution containing silver nanoparticles exhibited surface plasmon resonance peak at 450 nm, FT-IR showed vibrational frequencies of the biomolecule involved in the reduction of Ag+ ion at 3410, 2925, 2851, 1449 and 1031 cm-1. The XRD pattern at 38° (111), 44°(200) and 64° (220) confirmed the presence of silver nanoparticles with face-centered cubic structure while SEM microscopy analysis showed the synthesized silver nanoparticles to be mainly of spherical morphology with particle sizes ranging between 13-45 nm. Findings: Five indicator pathogens were selected and assayed to assess the efficacy of the synthesized AgNPs including Bacillussubtilis (gram-positive bacteria), Staphylococcus aureus (gram-positive bacteria), Escharichia coli (gram-negative bacteria), Streptococcus pneumonia (gram-negative bacteria) and Trichomonas vaginalis (Protozoa). The potency of the synthesized AgNPs was measured against gentamicin and chloramphenicol reference antibiotics. The toxic activity against all organisms is comparable with the two reference antibiotics and supports various other reports of the bioactivity of photosynthesized silver nanoparticles. Application: The antimicrobial activity obtained further revealed that the AgNPs were more potent against the growth of T. vaginalis, followed by the two gram-negative bacteria than the two gram-positive bacteria. The current investigation supports result of similar studies conducted on other medicinal plants and so have added value to the use of plants in ethno-medicine. The finding is encouraging and hence this biosynthesized silver nanoparticle may require further clinical studies for potential application against strains of antibiotic resistant bacteria. 

Keywords: Antimicrobial Assessment, Green Synthesis, Silver Nanoparticles, Euphorbia geniculata