CYANOBACTERIA ASSISTED BIO-REDUCTION OF SILVER NANOPARTICLE CONJUGATES AND STUDY ON THEIR CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY AGAINST PATHOGENIC BACTERIA

Green nanotechnology has recently emerged as an area of research involving more eco-friendly and energy-efficient approaches for the synthesis of inorganic nanoparticles. The point of the present investigation is to evaluate the capacity of selected strains of freshwater Cyanobacteria (Microalgae) for their capability to biosynthesize silver nanoparticles by utilizing both live biomass of microalgae and cell-free extract by suspending in AgNO₃ solution for 72 h of incubation period in both in presence of light and dark conditions. In most of the cases, silver nanoparticles were formed both in the presence of biomass as well as in the cell-free extract under continues light emission, which indicates that formation of silver nanoparticles involves an extracellular compounds. Synthesized silver nanoparticles were characterized by Ultraviolet-Visible (UV-Vis) Spectroscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Biosynthesis of silver nanoparticles was indicated by observing gradual colour change of the extract pale yellow to visible brownish-yellow. UV-Vis spectrophotometry study showed absorption maxima at 420-470 nm. The embedment and size of the synthesized silver nanoparticles were characterized by SEM and TEM. The bio-reducted silver nanoparticles size ranged between 20-22 nm depending on organism used in TEM analysis. The presence of bio-component in Cyanobacteria was confirmed by Fourier Transmittance Infrared Spectrum (FTIR) analysis, which is a source of nanoparticle synthesis. The antibacterial activity of synthesized silver nanoparticles was studied on clinically important gram+ve and gram –ve pathogenic bacteria.