title: Extracellular biosynthesis of magnetite using fungi.
abstract: The development of synthetic processes for oxide nanomaterials is an issue of considerable topical interest. While a number of chemical methods are available and are extensively used, the collaborations are often energy intensive and employ toxic chemicals. On the other hand, the synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures and pressures, and at neutral pH (examples include magnetotactic bacteria, diatoms, and S-layer bacteria). Here we show that nanoparticulate magnetite may be produced at room temperature extracellularly by challenging the fungi, Fusarium oxysporum and Verticillium sp., with mixtures of ferric and ferrous salts. Extracellular hydrolysis of the anionic iron complexes by cationic proteins secreted by the fungi results in the room-temperature synthesis of crystalline magnetite particles that exhibit a signature of a ferrimagnetic transition with a negligible amount of spontaneous magnetization at low temperature.
authors.affiliation: Nanoscience Group, Materials Chemistry Division, National Chemical Laboratory, Pune, India.
authors.forename: Atul
authors.initials: A
authors.lastname: Bharde
authors.forename: Debabrata
authors.initials: D
authors.lastname: Rautaray
authors.forename: Vipul
authors.initials: V
authors.lastname: Bansal
authors.forename: Absar
authors.initials: A
authors.lastname: Ahmad
authors.forename: Indranil
authors.initials: I
authors.lastname: Sarkar
authors.forename: Seikh Mohammad
authors.initials: SM
authors.lastname: Yusuf
authors.forename: Milan
authors.initials: M
authors.lastname: Sanyal
authors.forename: Murali
authors.initials: M
authors.lastname: Sastry
mesh_terms: D003460:Crystallization / Q000379:methods*; D045604:Extracellular Fluid / Q000737:chemistry / Q000378:metabolism; D052203:Ferrosoferric Oxide / Q000737:chemistry* / Q000378:metabolism*; D005670:Fusarium / Q000378:metabolism*; D008280:Magnetics; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D013499:Surface Properties; D020172:Verticillium / Q000378:metabolism*
chemical_list: D052203:Ferrosoferric Oxide