1.       Introduction

 Nanotechnology refers to an emerging field of science that includes synthesis and development of various Nano materials. Nanoparticles can be defined as objects ranging in size from 1-100 nm that due to their size may differ from the bulk material. Presently, different metallic Nano materials are being produced using copper, zinc, titanium, magnesium, gold, alginate and silver. Nanoparticles are being used for diverse purposes, from medical treatments, using in various branches of industry production such as solar and oxide fuel batteries for energy storage, to wide incorporation into diverse materials of everyday use such as cosmetics or clothes [1].

 1.1.  Synthesis of Nanoparticles

 Nanoparticles can be synthesized chemically or biologically. Many adverse effects have been associated with chemical synthesis methods due to the presence of some toxic chemical absorbed on the surface. Eco friendly alternatives to Chemical and physical methods are Biological ways of Nano particles synthesis using microorganisms [2,3], enzymes [4], fungus [5], and plants or plant extracts [6,7]. The development of these eco-friendly methods for the synthesis of Nano particles is evolving into an important branch of nanotechnology especially silver Nano particles, which have many applications [8-10].

 1.2.  Biosynthesis: Mechanism

 Biosynthesis of Nano particles by microorganisms is a green and eco-friendly technology. Diverse microorganisms, both prokaryotes and eukaryotes are used for synthesis of metallic Nano particles viz. silver, gold, and platinum, zirconium, palladium, iron, cadmium and metal oxides such as titanium oxide, zinc oxide, etc. These microorganisms include bacteria, actionmycetes, fungi and algae. The synthesis of Nano particles may be intracellular or extracellular according to the location of Nano particles [11,12].

 1.3.  Intracellular Synthesis of Nanoparticles by Fungi

 This method involves transport of ions into microbial cells to form Nano particles in the presence of enzymes. As compared to the size of extra cellular reduced Nano particles, the Nano particles formed inside the organism are smaller. The size limit is probably related to the particles nucleating inside the organisms [13].

 1.4.  Extracellular Synthesis of Nanoparticles by Fungi

 Extracellular synthesis of Nano particles has more applications as compared to intracellular synthesis since it is void of unnecessary adjoining cellular components from the cell. Mostly, fungi are known to produce Nano particles extra cellular because of their enormous secretary components, which are involved in the reduction and capping of Nano particles [13].

 1.5.  Microbes for Production of Nanoparticles

 Both unicellular and multi cellular organisms produce inorganic materials either intra- or extra cellular [14]. The ability of microorganisms like bacteria and fungi to control the synthesis of metallic Nano particles is employed in the search for new materials.

 Because of their tolerance and metal bioaccumulation ability, fungi have occupied the center stage of studies on biological generation of metallic Nano particles [15].

 2.       Types 

Silver: Silver Nano particles have proved to be most effective because of its good antimicrobial efficacy against bacteria, viruses and other eukaryotic micro-organisms [16,17]. They are undoubtedly the most widely used Nano materials among all, thereby being used as antimicrobial agents, in textile industries, for water treatment, sunscreen lotions etc [18,19]. Studies have already reported the successful biosynthesis of silver nano particles by plants such as Azadirachta Indica [20], Capsicumannuum [21] and Carica papaya [22]. 

Gold: Gold Nano particles (Au NPs) are used in immune chemical studies for identification of protein interactions. They are used as lab tracer in DNA fingerprinting to detect presence of DNA in a sample. They are also used for detection of amino glycoside antibiotics like streptomycin, gentamycin and neomycin. Gold Nano rods are being used to detect cancer stem cells, beneficial for cancer diagnosis and for identification of different classes of bacteria [23,24]. 

Alloy: Alloy Nano particles exhibit structural properties that are different from their bulk samples [25]. Since Ag has the highest electrical conductivity among metal fillers and, unlike many other metals, their oxides have relatively better conductivity [26], Ag flakes are most widely used. Bimetallic alloy Nano particles properties are influenced by both metals and show more advantages over ordinary metallic NPs [27]. 

Magnetic: Magnetic Nano particles like Fe₃O₄ (magnetite) and Fe₂O₃ (maghemite) are known to be biocompatible. They have been actively investigated for targeted cancer treatment (magnetic hyperthermia), stem cell sorting and manipulation, guided drug delivery, gene therapy, DNA analysis, and Magnetic Resonance Imaging (MRI) [28].

3.       Applications

Nano medicine has tremendous prospects for the improvement of the diagnosis and treatment of human diseases. Use of microbes in biosynthesis of Nano particles is an environmentally acceptable procedure. Nanotechnology has potential to revolutionize a wide array of tools in biotechnology so that they are more personalized, portable, cheaper, safer, and easier to administer.

4.       Conclusion

Due to their incredible properties, Nano particles have become significant in many fields in recent years such as energy, health care, environment, agriculture etc. Nano particle technologies have great potentials, being able to convert poorly soluble, poorly absorbed and labile biologically active substance into promising deliverable substances.

5.       Uses

·         The use of polymeric micelle Nano particles to deliver drugs to tumors.

·         The use of polymer coated iron oxide Nano particles to break up clusters of bacteria, possibly allowing more effective treatment of chronic bacterial infections.

·         The surface change of protein filled Nano particles has been shown to affect the ability of the Nano particle to stimulate immune responses. Researchers are thinking that these Nano particles may be used in inhalable vaccines.

·         Researchers at Rice University have demonstrated that cerium oxide Nano particles act as an antioxidant to remove oxygen free radicals that are present in a patient's bloodstream following a traumatic injury. The Nano particles absorb the oxygen free radicals and then release the oxygen in a less dangerous state, freeing up the Nano particle to absorb more free radicals.

·         Researchers are developing ways to use carbon Nano particles called Nano diamonds in medical applications. For example, Nano attached can be used to increase bone growth around dental or joint implants.

·         Researchers are testing the use of chemotherapy drugs attached to Nano diamonds to treat brain tumors.

·         Other researchers are testing the use of chemotherapy drugs attached to Nano diamonds to treat leukemia.

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