BIO SYNTHESIS OF NANOPARTICLES BY BACTERIA

PRESENTED BY

ROOPAVATH UDAY KIRANM.Tech 1st year

Centre for Nano science and TechnologyCourse: Synthesis & Characterization of Nano structured materialsCode : NST 616 Course instructor : Associate professor Dr. A. Vadivel Murugan .

OVERVIEW

• INTRODUCTION• GENERAL STRUCTURE OF BACTERIA• METHODS OF SYNTHESIS IN BACTERIA• EXAMPLES

INTRODUCTION

• Microbial synthesis of nanoparticles is a green chemistry approach that interconnects nanotechnology and microbial biotechnology.

• Although ultraviolet irradiation, aerosol, lithography, laser ablation, ultrasonic fields & photochemical synthesis are successful in synthesis of many nanoparticles they involve use of HAZARDOUS CHEMICALS.

• Biological nanoparticles are not mono dispersed and the rate of synthesis is slow.

• To overcome above, microbial cultivation methods, extraction techniques & combinatorial approach such as photo biological methods are used.

• Microbes are regarded as POTENT ECO-FRIENDLY GREEN FACTORIES.

• Drawbacks of bio synthesis :• Time consuming – Rate of production is slow• Difficulty in control over size distribution,

shape and crystallinity.• The nanoparticles are also not mono

dispersed.

Microbial resistance to most toxic heavy metals is due to:• Chemical detoxification • Ion efflux from cell by membrane proteins• Alteration in solubility

Interaction b/w metals n microbes for ?:• Bio remediation• Bio mineralization• Bio leaching• Bio corrosion

STRUCTURE OFBACTERIA

METHODS OF SYNTHESIS

Intracellular: Inside the cell, in cytoplasm or cytosol.

Extracellular : Out side the cell on the surface or between the cells inside a colony.

Intracellular synthesis of nanoparticles by bacteria

• Bioaccumulation • In order to release the intracellularly synthesized

nanoparticles, additional processing steps such as ultrasound treatment or reaction with suitable detergents are required.

• Bacillus subtilis 168 reduced water soluble ions to producing octahedral morphology inside the cell walls in the dimensions of 5–25 nm

• In Fe(III) reducing bacterium, Geobacter ferrireducens, gold was precipitated intracellularly in periplasmic space.

• Silver-based single crystals such as equilateral, triangles and hexagons with particle sizes up to 200 nm in periplasmic space of the bacterium were produced by Pseudomonas stutzeri AG259, a silver mine bacterium. This bacterium also produced a small number of monoclinic crystalline α-form silver sulfide acanthite () crystallite particles with the composition of silver and sulfur in the ratio 2:1.

• Normally, silver toxicity has been well detoxified by small periplasmic silver-binding proteins, which bind silver at the cell surface and by efflux pumps propels the incoming metals and protects the cytoplasm from toxicity. It has been believed that the organic matrix contains silver-binding proteins that provide amino acid moieties, which serve as nucleation sites for the formation of silver nanoparticles

Crystal topologies by P. stutzeri AG259. (a, b) Triangular, hexagonal, andspheroidal Ag-NPs found at different cellular binding sites ( withpermission from National Academy of Sciences, U.S.A.)

Dark-field TEM image of S. algae cells showing the presence of platinumnanoparticles deposited in periplasmic space ( with permissionfrom Elsevier publishers).

TEMof negatively stained cells of M. gryphiswaldense displaying themagnetosome chain and isolated magnetosomes. (a). Enlarged view of the magnetosome chain within M. gryphiswaldense. The bar denotes 0.1 μm. (b) Isolated magnetosome particles with intact magnetosome membranes. Magnetosome membrane is indicated by arrows

TEMimage of flocculated UO2 nanoparticles associatedwith Desulfosporosinus spp.bacteria (arrow). Inset, high-resolution TEMimage of isolated particles

Extracellular synthesis of nanoparticles by bacteria• Extracellular bio mineralization, biosorption, complexation or

precipitation. When the cell wall reductive enzymes or soluble secreted enzymes are involved in the reductive process of metal ions then it is obvious to find the metal nanoparticles extracellularly.

• With the change in pH of the solution, various shapes and sizes were formed.

• The culture supernatants of Enterobacteriaceae (Klebsiella pneumonia, E. coli andEnterobacter cloacae) also rapidly synthesized silver nanoparticles by reducing Ag+ to Ag0. These particles ranged in size from 28.2 nm to 122 nm with an average size of 52.5 nm. With the addition of piperitone, silver ion reduction was partially inhibited, which showed the involvement of nitroreductase enzymes in the reduction process.

• Titanium nanoparticles of spherical aggregates of 40–60 nm were produced extracellularly using the culture filtrate of Lactobacillus sp. at room temperature. These titanium nanoparticles were lighter in weight and high resistance to corrosion and have enormous applications in automobiles, missiles, airplanes, submarines, cathode ray tubes and in desalting plants and has promising future role in cancer chemotherapy and gene delivery.

• Immobilized Rhodobacter sphaeroides extracellularly produced spherical shaped zinc sulfide (ZnS) semiconductor nanoparticles of 8 nm in size [88]. In analogous, immobilized purple, nonsulfur photosynthetic bacterium, R. sphaeroides produced extracellularly fcc structured lead sulfide (PbS) nanoparticles of size 10.5± 0.15 nm with monodispersed spherical morphology.

• The extracellular production of nanoparticles has wider applications in optoelectronics, electronics, bioimaging and in sensor technology than intracellular accumulation.

Characterization of PbS nanoparticles synthesized by immobilized R. sphaeroides (a) TEM image (b) HRTEM image (c) (200) lattice fringes of denoted area (d) correspondingSAED pattern

Thank you for your kind attention..!