Satyajyoti Senapati

Extracellular biosynthesis of silver nanoparticles using the fungus Fusarium oxysporum

The development of reliable, eco-friendly processes for the synthesis of nanomaterials is an important aspect of nanotechnology today. One approach that shows immense potential is based on the biosynthesis of nanoparticles using biological micro-organisms such as bacteria. In this laboratory, we have concentrated on the use of fungi in the intracellular production of metal nanoparticles. As part of our investigation, we have observed that aqueous silver ions when exposed to the fungus Fusarium oxysporum are reduced in solution, thereby leading to the formation of an extremely stable silver hydrosol. The silver nanoparticles are in the range of 5-15 nm in dimensions and are stabilized in 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 rational, fungal-based method for the synthesis of nanomaterials over a range of chemical compositions, which is currently not possible by other microbe-based methods.

BIOREDUCTION OF AUCL4− IONS BY THE FUNGUS, VERTICILLIUM SP. AND SURFACE TRAPPING OF THE GOLD NANOPARTICLES FORMED

Fungi make piles of gold! A green-chemistry route, based on the bioreduction of AuCl 4 - ions by the fungus Verticillium sp., for the formation of gold nanoparticles is demonstrated. The TEM micrograph shows a single Verticillium cell after reaction with gold ions and entrapment of gold nanoparticles on the cell wall and cytoplasmic membrane.

Extracellular Synthesis of Gold Nanoparticles by the Fungus Fusarium oxysporum

A green chemistry approach to nanoparticle synthesis is the exciting possibility opened up by the fungus Fusarium oxysporum. The fungus, when exposed to aqueous AuCl 4 − ions, reduces the metal ions; this leads to the extracellular formation of gold nanoparticles.

Intracellular synthesis of gold nanoparticles by a novel alkalotolerant actinomycete, Rhodococcus species

The development of reliable, eco-friendly processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In this paper, we report on the use of an alkalotolerant actinomycete (Rhodococcus sp.) in the intracellular synthesis of gold nanoparticles of the dimension 5–15 nm. Electron microscopy analysis of thin sections of the gold actinomycete cells indicated that gold particles with good monodispersity were formed on the cell wall as well as on the cytospasmic membrane. The particles are more concentrated on the cytoplasmic membrane than on the cell wall, possibly due to reduction of the metal ions by enzymes present in the cell wall and on the cytoplasmic membrane. The metal ions were not toxic to the cells and the cells continued to multiply after biosynthesis of the gold nanoparticles.