title: Synthesis of silver nanoparticles using Dioscorea bulbifera tuber extract and evaluation of its synergistic potential in combination with antimicrobial agents.
abstract: BACKGROUND
  Development of an environmentally benign process for the synthesis of silver nanomaterials is an important aspect of current nanotechnology research. Among the 600 species of the genus Dioscorea, Dioscorea bulbifera has profound therapeutic applications due to its unique phytochemistry. In this paper, we report on the rapid synthesis of silver nanoparticles by reduction of aqueous Ag(+) ions using D. bulbifera tuber extract.
  
  
  RESULTS
  Phytochemical analysis revealed that D. bulbifera tuber extract is rich in flavonoid, phenolics, reducing sugars, starch, diosgenin, ascorbic acid, and citric acid. The biosynthesis process was quite fast, and silver nanoparticles were formed within 5 hours. Ultraviolet-visible absorption spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction confirmed reduction of the Ag(+) ions. Varied morphology of the bioreduced silver nanoparticles included spheres, triangles, and hexagons. Optimization studies revealed that the maximum rate of synthesis could be achieved with 0.7 mM AgNO(3) solution at 50°C in 5 hours. The resulting silver nanoparticles were found to possess potent antibacterial activity against both Gram-negative and Gram-positive bacteria. Beta-lactam (piperacillin) and macrolide (eryth-romycin) antibiotics showed a 3.6-fold and 3-fold increase, respectively, in combination with silver nanoparticles selectively against multidrug-resistant Acinetobacter baumannii. Notable synergy was seen between silver nanoparticles and chloramphenicol or vancomycin against Pseudomonas aeruginosa, and was supported by a 4.9-fold and 4.2-fold increase in zone diameter, respectively. Similarly, we found a maximum 11.8-fold increase in zone diameter of streptomycin when combined with silver nanoparticles against E. coli, providing strong evidence for the synergistic action of a combination of antibiotics and silver nanoparticles.
  
  
  CONCLUSIONS
  This is the first report on the synthesis of silver nanoparticles using D. bulbifera tuber extract followed by an estimation of its synergistic potential for enhancement of the antibacterial activity of broad spectrum antimicrobial agents.
authors.affiliation: Institute of Bioinformatics and Biotechnology, University of Pune, Pune, India.
authors.forename: Sougata
authors.initials: S
authors.lastname: Ghosh
authors.forename: Sumersing
authors.initials: S
authors.lastname: Patil
authors.forename: Mehul
authors.initials: M
authors.lastname: Ahire
authors.forename: Rohini
authors.initials: R
authors.lastname: Kitture
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Kale
authors.forename: Karishma
authors.initials: K
authors.lastname: Pardesi
authors.forename: Swaranjit S
authors.initials: SS
authors.lastname: Cameotra
authors.forename: Jayesh
authors.initials: J
authors.lastname: Bellare
authors.forename: Dilip D
authors.initials: DD
authors.lastname: Dhavale
authors.forename: Amit
authors.initials: A
authors.lastname: Jabgunde
authors.forename: Balu A
authors.initials: BA
authors.lastname: Chopade
mesh_terms: D000890:Anti-Infective Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D027742:Dioscorea / Q000737:chemistry*; D004357:Drug Synergism; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry*; D035281:Plant Tubers / Q000737:chemistry; D012834:Silver / Q000737:chemistry* / Q000494:pharmacology*; D012835:Silver Nitrate; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D000890:Anti-Infective Agents; D010936:Plant Extracts; D012834:Silver; D012835:Silver Nitrate