Open Access Devika et al., 1:12 http://dx.doi.org/10.4172/scientificreports.557 Research Article Open Access Open Access Scientific Reports Scientific Reports Open Access Volume 1 • Issue 12 • 2012 Keywords: Silver nanoparticles; Pleurotus ostreatus; Antimicrobial activity; Spectroscopic studies Introduction he development of environmentally benign materials like fungi for the synthesis of Ag-NPs ofers numerous beneits of eco-friendliness and compatibility for pharmaceutical and other biomedical applications, as they do not use toxic chemicals for the synthesis protocol. Several applications of nanoparticles are in the ield of drug/gene delivery vehicles [1]. here is an increasing commercial demand for nanoparticles due to their wide applicability in various areas, such as electronics, catalysis, chemistry, energy and medicine. New application of nanoparticles and nanomaterials are emerging rapidly [2,3]. Nanocrystalline Ag-particles have found tremendous applications in the ield of high sensitivity bio-molecular detection and diagnostics [4], antimicrobials and therapeutics [5,6]. One approach that shows immense potential is based on the biosynthesis of nanoparticles, using biological organisms such as bacteria. In this work, we have concentrated on the use of fungi in the extracellular production of metal nanoparticles. As part of our work, we have observed that aqueous silver ions, when exposed to the fungus Pleurotus ostreatus, are reduced in solution, thereby leading to the formation of an extremely stable silver particle. he Ag-NPs are in the range of 30 nm in dimensions, and are stabilized in the solution by proteins secreted by the fungus. It is believed that the reduction of the metal ions occurs by an enzymatic process, thus creating the possibility of developing a fungus-based method for the synthesis of nanoparticles. It has been well established that microorganisms are a virtually unlimited source, and have potential therapeutic applications. Materials and Methods Sample preparation All chemicals used were of analytical grade. P. ostreatus was grown E. Manikandan, Polymer Nanotechnology Centre (PNTC) & Dept. of Chemistry, B.S. Abdul Rahman University, Chennai-600048, India, E-mail: maniphysics@ gmail.com Received October 03, 2012; Published November 30, 2012 Citation: Devika R, Elumalai S, Manikandan E, Eswaramoorthy D (2012) Biosynthesis of Silver Nanoparticles Using the Fungus Pleurotus ostreatus and their Antibacterial Activity. 1:557 doi:10.4172/scientiicreports.557 Copyright: © 2012 Devika R, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Metal Nanoparticles (m-NPs) are explored in recent years as an alternative approach to effectively kill drug resistant pathogenic microorganisms. Silver nanoparticles (Ag-NPs) are the metal of choice for antibiotic resistant microbes. Synthesis of silver nanoparticles through biological route is preferred over chemical route to promote green chemistry. In the present study, an eco-friendly process for the synthesis of nanomaterials, using a fungus (Pleurotus ostreatus) has been attempted. The fungus supernatant of seed culture was used for the biosynthesis of Ag-NPs. The aqueous silver ions (Ag + ) were reduced to silver metal nanoparticles (Ag m-NPs), when treated with the fungal supernatant. After 72 h of treatment, silver nanoparticles (Ag-NPs) were obtained. These Ag-NPs were characterized by UV-Vis, Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and Transmission Electron Microscopes (TEM) were used to identify these NPs. The nanoparticles exhibited maximum absorbance peak at 440 nm in UV–Vis spectroscopy. From the XRD pattern of Ag-NPs exhibited 2θ~38.2° values, corresponding to the silver Ag (111) crystalline phase indexed. The NPs surface morphology revealed from SEM and TEM images shows formation of well-dispersed Ag-NPs of 50 nm, and the presence of silver was conirmed by EDX analysis. The microbes selected for the present study for the antibacterial activity were Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Vibrio cholera. This study conclude that the nanoparticles synthesized from the fungus open up the exiting possibility of rational strategy of biosynthesis of nanomaterials, and thus, silver nanoparticles has great potential as antimicrobial compound against pathogenic microorganisms studied, and that it can be used in the treatment of infectious diseases caused by bacteria. Biosynthesis of Silver Nanoparticles Using the Fungus Pleurotus ostreatus and their Antibacterial Activity R. Devika 1 , S. Elumalai 1 *, E. Manikandan 2 * and D. Eswaramoorthy 1 1 P.G. and Research Dept. of Plant Biology & Plant Biotechnology, Presidency College, Chennai, India 2 Polymer Nanotechnology Centre (PNTC) & Dept. of Chemistry, B.S. Abdul Rahman University, Chennai, India in seed medium containing glucose 20 g/l, glycerol 30 g/l, peptone 8 g/l, NaNO 3 2 g/l, MgSO 4 1 g/l and soyabean meal 20 g/l, the pH was adjusted to 6.5 ± 0.2. he lasks were incubated in the incubator shaker at 1800 rpm at 25°C. Ater 3 days of incubation, the mycelia were separated by centrifugation (5000 rpm) and washed thrice with deionized water. he washed mycelia were suspended in deionized water, the aqueous extract obtained ater separation of mycelia suspension was challenged with 100 ml of 1 mM silver nitrate [Ag(NO 3 ) 2 ]. It is well known that Ag-NPs exhibit yellowish brown color in aqueous solution due to excitation of surface plasmon vibrations in Ag-NPs [7]. A bottle of the fungal cells ater removal from the culture medium, and before immersion in 1 mM Ag(NO 3 ) 2 solution. he fungal cells provided a pale (yellow) color, and the bottle containing the fungal cells ater immersion in 1 mM Ag(NO 3 ) 2 solution for 72 hours can clearly be observed that the previous pale color of the reaction mixture has changed to a darker shade ater 72 hours of reaction. he appearance of the yellowish- brown color in solution containing the biomass was a clear indication of the formation of Ag-NPs in the reaction mixture. he brown color *Corresponding authors: S. Elumalai, P.G. and Research Dept. of Plant Biology & Plant Biotechnology, Presidency College, Chennai-600005, India, E-mail: anananadal@gmail.com