Green Synthesis, Characterization And Antimicrobial Evaluation Of Silver And Zinc Oxide Nanoparticles From Extracts Of Bidens Pilosa

Abstract

There has been rampant outbreak of infectious diseases and various antibiotics have been introduced to treat these infections; however, they are turning out to be less effective due to their abuse leading to emergence of antimicrobial resistant infections. Various antiseptics have been used but their active ingredients are becoming ineffective to most resistant strains of bacteria. However, nanotization of antimicrobial agents has shown improvement of their disinfecting efficacy since nanoparticles have proved to have effective antimicrobial activity, even to resistant strains of microbes. In this study, nanotization of chemical constituents of Bidens pilosa was carried out because traditionally this plant is proven to have antimicrobial activity. In this study, biosynthesis of silver nanoparticles (AgNPs), zinc oxide-silver nanoparticles (ZnO-AgNPs) and zinc oxide nanoparticles (ZnONPs) using the seed, leaf and root extracts of Bidens pilosa with Silver nitrate and Zinc nitrate solutions, is reported. Extracts of Bidens pilosa contain a variety of bio-molecules such as polyphenols and water soluble heterocyclic compounds which reduce metal ions and stabilize nanoparticles. The plant (Bidens pilosa) was harvested; its seeds, leaves and roots were plucked, washed, dried under shed and crushed. The powders were dissolved in water to form extracts. The extracts were used to make AgNPs, ZnONPs and ZnO-AgNPs. The nanoparticles were characterized using UV-Vis spectroscopy, Fourier Transform Infrared, Raman spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Diffraction and Atomic Force Microscopy. The antimicrobial activity of the nanoparticles was determined using agar well diffusion method. The most active nanoparticles were used as active ingredients in the formulation an antiseptic. The antimicrobial activity of the antiseptic was determined. The UV-Visible spectra showed a complete reduction of Ag+ ions to Ag0 with Plasmon resonance bands at around 410nm which is characteristic of AgNPs and formation of ZnONPs with a Plasmon resonance bands around 370nm. The synthesized nanoparticles had an average size of 2-20nm and were sphere-shaped without significant agglomeration as revealed from the SEM and TEM analysis. The synthesized AgNPs, ZnONPs and ZnO-AgNPs exhibited face–centered cubic crystals as demonstrated from XRD studies. FT-IR and Raman spectra of the seed, leaf and root extracts of Bidens pilosa, AgNPs, ZnONPs and ZnO-AgNPs revealed presence of vii functional groups C-O, O-H, =C–H, aromatic C-H bending, O-H, C=O, C=C aromatic and thiol groups attached to them. This indicated that these functional groups capped and stabilized the nanoparticles. Anti-Microbial activity of synthesized AgNPs, ZnONPs and ZnO-AgNPs against Escherichia coli, Staphylococcus aureus and a fungus Candida albicans were studied. Clear zones of inhibition were observed for the nanoparticles against the microorganisms. The ZnO-AgNPs obtained from the root extract of composition 0.8 Ag/0.2 ZnO had the highest antimicrobial activity. The ZnO-AgNPs obtained using root extracts of composition 0.8 Ag/0.2 ZnO were found to be effective as an active ingredient to make a hand sanitizing antiseptic against E. coli, and S. aureus bacteria and the fungus C. albicans.