Biogenic Synthesis of Silver Nanoparticles Using Scenedesmus abundans and Evaluation of Their Antibacterial Activity

Silver nanoparticle (AgNP) was synthesized using the cell free extract of Scenedesmus abundans with AgNO3. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and Photoluminescence. Bioreduction of Ag+ ions showed a gradual change in the colour of the extract and nanoparticles were synthesized having the range of 420–440？nm under UV-visible spectrum. The antibacterial efficacy was assessed against pathogenic bacteria E. coli, Klebsiella pneumoniae, and Aeromonas hydrophila. The present study revealed that the AgNPs prepared from Scenedesmus abundans show antibacterial efficacy against the test pathogens. The bioaccumulation of silver particles makes the organism potential candidate for ecofriendly silver biorecovery system and S. abundans can be used as a source of silver nanoparticles. 1. Introduction Nanoparticles are gaining the interest in it due to their unique characteristics such as electronic, mechanical, optical, magnetic, chemical properties [1, 2] and high surface to volume ratio which differ significantly with bulk materials [3, 4]. In nanotechnology, the formation of nanoparticles has the method that mainly involved the process of separation deformation and transformation of materials to atoms or molecules [5]. The synthesis of nanoparticles can occur by different methods such as dry, wet, and through computational nanotechnology. Basically dry nanotechnology concentrates on surface science, physical chemistry, and structure of organic and inorganic materials. Wet nanotechnology deals with biological systems that exist primarily in water base system, such as enzymes, membranes, and cellular components. Computational nanotechnology comprises modelling and stimulation of complex nanometer. The novel metal nanoparticles had attended much interest due to their vast applications in diverse areas such as optoelectronics, cosmetics, photo catalysis, diodes, piezoelectric devices, fluorescent tubes, laser, sensor, photography, biological labeling, photonics coatings, packaging, and drug delivery system [5–9]. Now a days nanomaterials are produced by industries for commercial application having many benefits. Green synthesis of nanoparticles attracts many researchers and industries. Many microorganisms are utilized for the synthesis of nanoparticles intracellularly as well as extracellularly [10–13]. The mechanism behind the synthesis of silver nanoparticles was not known before but it was hypothesized later that the enzymes NADH-dependent nitrate