title: Biosynthesis, purification and characterization of silver nanoparticles using Escherichia coli.
abstract: The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology. Nanomaterials may provide solutions to technological and environmental challenges in the areas of solar energy conversion, catalysis, medicine, and water-treatment. The development of techniques for the controlled synthesis of nanoparticles of well-defined size, shape and composition, to be used in the biomedical field and areas such as optics and electronics, has become a big challenge. Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. One of the options to achieve this objective is to use 'natural factories' such as biological systems. This study reports the optimal conditions for maximum synthesis of silver nanoparticles (AgNPs) through reduction of Ag(+) ions by the culture supernatant of Escherichia coli. The synthesized silver nanoparticles were purified by using sucrose density gradient centrifugation. The purified sample was further characterized by UV-vis spectra, fluorescence spectroscopy and TEM. The purified solution yielded the maximum absorbance peak at 420 nm and the TEM characterization showed a uniform distribution of nanoparticles, with an average size of 50 nm. X-ray diffraction (XRD) spectrum of the silver nanoparticles exhibited 2theta values corresponding to the silver nanocrystal. The size-distribution of nanoparticles was determined using a particle-size analyzer and the average particle size was found to be 50 nm. This study also demonstrates that particle size could be controlled by varying the parameters such as temperature, pH and concentration of AgNO(3).
authors.affiliation: Division of Molecular and Cellular Biology, Department of Biotechnology, Kalasalingam University, Anand Nagar, Krishnankoil, 626190, Tamil Nadu, India. lvsangs@yahoo.com
authors.forename: Sangiliyandi
authors.initials: S
authors.lastname: Gurunathan
authors.forename: Kalimuthu
authors.initials: K
authors.lastname: Kalishwaralal
authors.forename: Ramanathan
authors.initials: R
authors.lastname: Vaidyanathan
authors.forename: Deepak
authors.initials: D
authors.lastname: Venkataraman
authors.forename: Sureshbabu Ram Kumar
authors.initials: SR
authors.lastname: Pandian
authors.forename: Jeyaraj
authors.initials: J
authors.lastname: Muniyandi
authors.forename: Nellaiah
authors.initials: N
authors.lastname: Hariharan
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Eom
mesh_terms: D002499:Centrifugation, Density Gradient; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry / Q000382:microbiology* / Q000648:ultrastructure; D010316:Particle Size; D012834:Silver / Q000737:chemistry* / Q000302:isolation & purification*; D012835:Silver Nitrate / Q000494:pharmacology; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D003470:Culture Media; D012834:Silver; D012835:Silver Nitrate