Bionanoparticles Synthesis and Antimicrobial Applications

Bionanoparticles: synthesis and antimicrobial applications

K. Sahayaraj* and S. Rajesh

Crop Protection Research Centre, Department of Advanced Zoology and Biotechnology, St. Xavier’s College (Autonomous), Palayamkottai – 627 002, Tamil Nadu, India, Tel: + 91 462 4264376, Fax: + 91 462 256 1765, *E-mail: [email protected],

It has been know that silver and its compounds have strong inhibitory and microbicidal activities for bacteria, fungi, and virus. Compared with other metals, silver exhibits higher toxicity to microorganism while it exhibits lower toxicity to mammalian cells. More recent advancement in researches on metal nanoparticles, silver nanoparticles (SNPs) has lot of scope for health care products such as burn dressings, scaffolds, water purification systems, antimicrobial applications and medical devices. Few researches focus for agriculture application. Hence, many people tried to synthesis SNPs with a variety of synthesis methods including chemical reduction, electrochemical techniques, photochemical reactions, and now a day via green chemistry route. Use of plants and microbes in synthesis of SNPs is quite novel method as it coast effective and environmental friendly and easily scaled up for large scale synthesis. In this chapter we highlighted about the various plants, bacteria, fungi and actinmycetes used in this process, synthesizing methodology; nanoparticles size, shape, and their application as antimicrobials in in elaborate manner. We also highlighted the basic mechanism by which SNPs interact with microbes and future recommendations.

1. Introduction

Bio-nanotechnology has emerged as integration among biotechnology and nanotechnology for developing biological synthesis and environmental-benign technology for synthesis of nanomaterials. The idea of nanotechnology was coined by physicist Professor Richard Feynman in his historic talk “there’s plenty of room at the bottom” (Feynman, 1959), though the term nanotechnology was introduced by Tokyo Science University Professor Norio Taniguchi (Taniguchi, 1974). We specifically regarded nanoparticles as clusters of atoms in the size of 1-100 nm. ‘Nano’ is a Greek word synonymous to dwarf meaning extremely small. The use of nanoparticles is gaining impetus in the present century as they posses defined chemical, optical and mechanical properties. Among them, the metallic nanoparticles are most promising as they contain remarkable antibacterial properties due to their large surface area to volume ratio, which is of interest to researchers due to the growing microbial resistance against metal ions, antibiotics, and the development of resistant strains (Rai et al., 2009; Gong et al., 2007). A list of some of the applications of nanomaterials to biology or medicine or agriculture are fluorescent biological labels, drug and gene delivery, bio-detection of pathogens, biosciences, detection of proteins, probing of DNA structure, tissue engineering, tumour destruction via heating (hyperthermia), separation and purification of biological molecules and cells, MRI contrast enhancement, pagokinetic studies, antimicrobials, and anti insect molecules Bio-Nanotechnology combines biological principles with physical and chemical approaches to produce nano-sized particles with specific functions. It also represents an economic substitute for chemical and physical methods of nanoparticles formation. These method of synthesis can be divided into intracellular and extracellular (Ahmad et al., 2005) with three main steps, which must be evaluated based on green chemistry perspectives, including (1) selection of solvent medium, (2) selection of environmentally benign reducing agent, and (3) selection of nontoxic substance for the Ag NPs stability. Metallic nanoparticles have a high definite surface area and a high fraction of surface atom; have studied extensively because of their exceptional physicochemical characteristics including catalytic, optical properties, electron properties etc. Silver, Aluminum, Gold, Zinc, Carbon, Titanium, Palladium, Iron, Fullerenes, Copper etc have been rottenly used for the synthesis of nanoparticles. However, former three metals are most popular metals in bio-nonmaterial synthesis. Nanoscience will leave no field untouched by its ground breaking technical innovations; the agricultural sector is no exception (Joseph and Morrison, 2008). So far, the use of nanoscience in agriculture has been predominantly theoretical, but it has begun and will continue to have a significant effect in the main areas of plant disease management. Silver nanoparticles are used as antimicrobial agents in most of the public places such as elevators and railway stations in China. Besides, they are used as antimicrobial agents in surgically implanted catheters in order to reduce the infections caused during surgery and are proposed to possess anti-fungal, anti-inflammatory, anti-angiogenic and anti-permeability activities (Kalishwaralal et al., 2009; Gurunathan et al., 2009; Sheikpranbabu et al., 2009). Primarily, silver nanoparticles are considered as an alternative to silver ions (obtained from silver nitrate), which were used as antimicrobial agents. Silver was used as storage devices during historical periods and silver nitrate solution was directly used for wound healing during Second World War (Chu et al., 1988; Deitch et al., 1987; Margraff and Covey, 1977; Silver, 2003; Atiyeh et al., 2007; Law et al., 2008). Before the advent of silver nanoparticles, silver was the main component in the various creams for wounds. However, silver ions have the disadvantage of forming complexes and the effect of the ions remained only for a short time. This disadvantage has been overcome by the use of the silver

228 ©FORMATEX 2011

Science against microbial pathogens: communicating current research and technological advances A. Méndez-Vilas (Ed.)______________________________________________________________________________

nanoparticles which are in inert form and also exhibit antimicrobial function by inducing the production of reactive oxygen species such as hydrogen peroxide. In the forthcoming section, we discussed about various methods for the biosynthesis of nanoparticles.

2. Green synthesis

Green synthesis of nanoparticles can be done by suing five methods (Sharma et al., 2009). They were a) Polysaccharide method, b) Tollens method, c) Irradiation method, d) biological methods, and e) Polyoxometalates method. These methods are briefly described here bellow.

2.1. Polysaccharide method

In Polysaccharide method, Ag NPs are prepared using water and polysaccharides as a capping agent, or in some cases polysaccharides serve as both a reducing and a capping agent. For instance, synthesis of starch-Ag NPs was carried out with starch as a capping agent and β-D-glucose as a reducing agent in a gently heated system. Additionally, the binding interactions between starch and Ag NPs are weak and can be reversible at higher temperatures, allowing separation of the synthesized particles. Importantly, starch-protected nanoparticles can be easily integrated into systems for biological and pharmaceutical applications.

2.2. Tollens method

The Tollens synthesis method gives Ag NPs with a controlled size in a one-step process. In the modified Tollens procedure, Ag+ ions are reduced by saccharides in the presence of ammonia, yielding Ag NP films with particle sizes from 50–200 nm, Ag hydrosols with particles in the order of 20–50 nm, and Ag NPs of different shapes.

2.3. Irradiation method

Ag NPs can be successfully synthesized by using a variety of irradiation methods. For example, laser irradiation of an aqueous solution of Ag salt and surfactant can fabricate Ag NPs with a welldefined shape and size distribution. No reducing agent is required in this method.

2.4. Biological method

Extracts from bioorganisms may act both as reducing and capping agents in Ag NPs synthesis. The reduction of Ag+ ions by combinations of biomolecules found in these extracts such as enzymes/proteins, amino acids, polysaccharides, and vitamins is environmentally benign, yet chemically complex. An extensive volume of literature reports successful Ag NPs using bioorganic compounds.

2.5. Polyoxometalates method

Polyoxometalates, POMs, have the potential of synthesizing Ag NPs because they are soluble in water and have the capability of undergoing stepwise, multi electron redox reactions without disturbing their structure.

3. Biosynthesis of silver nanoparticles

Different types of physical and chemical methods are employed for the synthesis of nanoparticles. The use of these synthesis methods requires both strong and weak chemical reducing agents and protective agents like sodium borohydride, sodium citrate and alcohols. These agents are mostly toxic, flammable, cannot be easily disposed off due to environmental issues and also show a low production rate (Mohanpuria et al., 2008; Rai et al., 2008; Sharma et al., 2009; Bar et al., 2009a, 2009b). It leads to in search of alternatives which could be ecofriendly and does not cause any harm to human and domestic animals health. One such method is biological methods where microbes and plants used either as reducing agents or protective agents. Many biological organisms, both unicellular and multicultural are know to produce inorganic materials either intra- or extra cellular, often of nanoscale dimensions and of exquisite morphology and hierarchical assembly. The biosynthesis of nanoparticles employs use of biological agents like bacteria, fungi, actinomycetes, yeast, algae and plants (Rai et al., 2008; Thakkar et al., 2010, Margarita, 2011). The rate of reduction of metal ions using biological agents is found to be much faster and also at ambient temperature and pressure conditions. Here, we summarize some of the organisms used in the biosynthesis of nanomaterials and describe the properties that should be inherent for the production of nanoparticles of desired characteristics.

3.1. Simple method for the synthesis

The acidophillic fungus, Verticillium sp., was isolated from the Taxus plant and maintained on potato-dextrose agar slants at 25°C. The fungus was grown in 500 ml Erlenmeyer flasks each containing 100 ml MGYP medium, composed

229©FORMATEX 2011

Science against microbial pathogens: communicating current research and technological advances A. Méndez-Vilas (Ed.)_______________________________________________________________________________

of malt extract (0.3%), glucose (1.0%), yeast extract (0.3%), and peptone (0.5%) at 25–28°C under shaking condition (200 rpm) for 96 h. After 96 h of fermentation, mycelia were separated from the culture broth by centrifugation (5000 rpm) at 10°C for 20 min and the settled mycelia were washed thrice with sterile distilled water. Ten grams of the harvested mycelial mass was then re-suspended in 100 ml of 2 ´ 10–4 aqueous AgNO3 solution in 500 ml Erlenmeyer flasks at pH 5.5–6.0. The whole mixture was thereafter put into a shaker at 28°C (200 rpm) and the reaction carried out for a period of 72 h. The biotransformation was routinely monitored by visual inspection of the biomass as well as measurement of the UV-vis spectra from the fungal cells (Sastry et al., 2003). Instead of Verticillium fungi can be used for the synthesis. PH, temperature, rpm and incubation period should be determined by the investigator based upon their experience for mass scale production of nanomaterials.

3.2. Merits

Fungi, due to their tolerance and bioaccumulation ability of metals, are taking the centre-stage of studies on biological metal nanoparticle generation. A few advantages of using fungal mediated green approach for the synthesis of nanoparticles are as follow: Economic viability, ease in scale up and handling, thus making it possible to easily obtain biomass for processing, and large-scale secretion of extracellular enzymes.

3.3. Synthesis of nanoparticles by Fungus

Eukaryotic organisms such as fungi may be used to grow nanoparticles of different chemical composition and sizes. A number of different genera of fungi have been investigated in this effort and it has been shown that fungi are extremely good candidate and as a “Nanofactory” for the synthesis of metal nanoparticles especially silver nanoparticles. In addition to good monodispersity, nanoparticles with well defined dimensions can be obtained by using fungi. This has been experimentally first proved by Mukherjee et al.(2001) where bioreduction of aqueous AuCl4

+ was carried out using the fungus Verticillium sp. that led to the formation of gold nanoparticles with fairly well-defined dimensions and good monodispersity. Biosyntehsis of nanoparticles have been takes place extra cellular, intera cellular and surface of the cell wall. Extra cellular synthesis has been observed in Fusarium oxysporum with silver and gold–silver nanoparticles (Ahmad et al., 2005). The reduction of silver ions by Fu. oxysporum strains has been attributed to a nitrate-dependent reductase and a shuttle quinine extracellular process. Bhainsa and D’Souza (2006) and Basavaraja et al. (2007) reported the extracellular synthesis of silver nanoparticles by the fungi, Aspergillus fumigatus and Fusarium semitectum, respectively. Many reports on the synthesis of metal and semi-conductor nanoparticles using yeast and fungi have been appeared. Silver nanoparticles in the range of 2-5 nm were synthesized extracellularly by a silver tolerant yeast strain MKY3 (Kowshik et al., 2003). Investigations carried out on 20 different fungi reveals that fungi are extremely good candidates in synthesis of metal and metal sulphides nanoparticles (Ahmad et al., 2005; Mukherjee et al., 2001). The shift from bacteria to fungi as a means of developing natural “nano-factories” has the added advantage that downstream processing and handling of biomass would be much simpler (Sastry et al., 2003). The fungi Verticillum sp., Fu. oxysporum, Fu. semitectum and Aspergillus flavus have shown the capability of the nanometal production either extra or intracellularly (Mukherjee et al., 2002; Bhainsa and D’Souza, 2006). Latter, Gajbhiye et al. (2009) reported the extracellular biosynthesis of silver nanoparticles using a common fungus, Alternaria alternata. These silver nanoparticles were evaluated for their part in increasing the antifungal activity of fluconazole against Phoma glomerata, Phoma herbarum, Fu. semitectum, Trichoderma sp., and Candida albicans. The synthesis of silver particles using soil dwelled Aspergillus niger strains was investigated by Sadowski et al. (2008a, 2009b). It was presented (Duran et al., 2005) that enzyme hydrogenase is present in a filtrate broth which obtained from Fu. oxysporum. The silver nanoparticles production capacity has been depended on the reductase/electron shuttle relationships. The reduction of metal ions occurs on the surface by the enzymes presented in the cell wall (Mukherjee et al., 2001). The extracellular enzymes such as naphthoquinons and anthraquinones showed excellent redox properties, they can act as electron shuttle in silver ions reduction. In 2009, Kathiresan and coworkers exploited the marine fungus, Penicillium fellutanum from mangrove sediment for synthesis of stable silver nanoparticles (Kathiresan et al., 2009). In 2009, Balaji and co-workers synthesized stable silver nanoparticles using culture filtrates of Cladosporium cladosporioides, a commonly available fungus found in marshland regions (Balaji et al., 2009).

3.4. Synthesis of nanoparticles by bacteria, yeast and actinomycetes

Specific bacteria can be used for the synthesis of specific bacteria-based nanoparticles. Fore instance, some of well known examples of bacteria include magnetic bacteria for magnetic nanoparticles, S-layer bacteria for gypsum and calcium carbonate layer and silver mine-inhabiting Pseudomonas spp. that reduces silver ions to form silver nanoparticles. Furthermore, nanocrystal of gold, silver and their alloys have been synthesized within the cells of lactic acid bacteria (Dubey et al., 2009). Klaus et al. (1999) reported biosynthesis of silver based single crystals by using Pseudomonas stutzeri AG259. The formation of extracellular and intracellular silver nanoparticles by bacteria has been investigated (Lengke et al., 2007). A significant part in nanobiotechnology deals with the synthesis of silver nanoparticles of different chemical compositions, sizes, shapes, and polydispersity. Shirley and co-workers reported the

230 ©FORMATEX 2011


antibacterial activity of silver nanoparticles synthesized from novel strain of Streptomyces sp. (Shirley et al., 2010). The novel silver nanoparticles exhibited a tremendous potential antibacterial activity against the multi drug resistant gram positive and gram negative bacterial strains. Beveridge and co-workers (Beveridge and Murray, 1980) have demonstrated that gold particles of nanoscale dimensions may be readily precipitated within bacterial cells by incubation of the cells with Au3+ ions. Fu et al. (2000) reported biosorption and bioreduction of silver ions by Lactobacillus sp. A09. Nair and Pradeep (2002) showed the formation of submicron crystallites of Ag, Au and Ag-Au alloy assisted by live Lactobacillus strains. Biosorption and Bioreduction of diamine silver complex by dried Corynebacterium sp. SH09 and Aeromonas sp. SH10 isolated from a gold mine by Huang et al. (2007). Many microorganisms produce inorganic materials either intra or extracellularly. Well-known example is magnetotactic bacteria which are able to synthesize magnetic nanoparticles (Bazylinski and Frankel, 2004). Magnetotactic bacteria are motile that move along geometric field lines. They produce magnetosomes; unique intracellular structure contains a magnetic particle, in narrow range of very low oxygen concentration. Magnetotactic bacteria usually mineralize either oxide magnetite Fe3O4 or iron sulfide Fe3S4 – greigite. An extracellularly preparation of metal nanoparticles generally involves the reduction of metal ions in solution. Bacillus licheniformis is a gram positive, thermophilic bacterium, commonly found in the soil. Novel method of biosynthesis of silver nanoparticles using a combination of culture supernatant of Bacillus subtilis and microwave irradiation was proposed by Saifuddin and coworkers (Saifuddin et al., 2009). The formation of nanoparticles by this method was extremely rapid with smaller size range of 5 -50 nm. Shiying et al. (2007) reported biosynthesis of gold nanoparticles by using bacteria Rhodopseudomonas capsulate. Ahmad et al. (2007) employed supernatant of Enterobacteria culture for the Ag nanoparticles synthesis. Filamentous Cyanobacterium Plectonema boryanum strain has been successfully used for synthesis of Ag nanoparticles (Maggy et al., 2007). Prasad et al. (2007) reported synthesis of titanium nanoparticles with the assistance of eco-friendly Lactobacillus sp. The formation of extracellular silver nanoparticles by photoautotrophic cyanobacterium Plectonema boryanum had been described by Lengke et al. (2007). A rapid method for synthesizing silver nanoparticles by treating the aqueous silver nitrate solution with culture supernatants of different strains of Enterobacteria such as Klebsiella pneumonia has been described (Shahverdi et al., 2007; Mokhtari et al., 2009). The process of synthesis was quite fast, the silver nanoparticles were formed within 5 min. The particle size histogram of silver nanoparticles showed the particle size range in between 28.2 nm to 122 nm with the average size of 52.5 nm. Silver nanoparticles in the range of 50 nm were synthesized by supernatant of Bacillus licheniformis (Kalishwaralal et al., 2008). Other chemicals are also been used for the synthesis. For instance Holmes et al. (1995) have shown Klebsiella aerogenes when exposed to Cd2+ ions resulted in intracellular formation of CdS nanoparticles in size range 20-200 nm. Latter, Kowshik et al.(Kowshik et al., 2002; 2003) have identified yeast Torulopsis sp. being capable of intracellular synthesis of PbS crystallite when exposed to aqueous Pb2+ ions and CdS nanoparticles synthesized intracellularly by using Schizosaccharomyces pombe (yeast cells).

4.1. Silver nanoparticles synthesis using plant extracts

An important branch of biosynthesis of nanoparticles is the use of plant extract for biosynthesis reaction. The name, metal used for the biosynthesis, particle size and shape is presented in Table 1. Cinnamon zeylanicum bark is widely used as a spice. It is principally employed in cooking and in medicine, it acts like other volatile oils and was once used as a cure for colds and to treat diarrhoea. Cinnamon zeylanicum bark is high in antioxidant activity. The essential oil of cinnamon also has antimicrobial properties, which can aid in the preservation of certain foods (Sathishkumar et al., 2009). Cinnamon zeylanicum bark has been reported to have remarkable pharmacological effects in the treatment of type II diabetes and insulin resistance. It was found to synthesize AgNP’s with a size of 30–40 nm. Coriandrum sativum leaves extract have minerals and vitamin contents including calcium, phosphorus, iron, carotene, thiamine, riboflavin, and niacin. They also contain sodium and oxalic acid. Aloe vera is a perennial succulent belonging to the Liliaceal family, and it is a cactus-like plant that grows in hot, dry climates. Recently, the extract of A. vera plant has been successfully used to synthesize single crystalline triangular gold nanoparticles (~50-350 nm in size) and spherical silver nanoparticles (~15 nm in size) in high yield by the reaction of chloroaurate ions for Au and silver ions for Ag with the extract of the Aloe vera plant (Chandran et al., 2006). Very recently Indium oxide and A. vera plant-based nanoparticles with particle sizes of 5-50 nm were synthesized by Maensiri et al. (2008). Latter, Zhang et al. (2010) also synthesized in large quantities by reducing silver nitrate with A. vera pulp extract at room temperature.

Table 1. Bionanoparticles synthesized using botanicals with their size, shape and citations

Plant Parts used

Metal/ alloy

Size/shape Citations

Pelargonium graveolens Leaves Ag+ 16 to 40 nm / quasilinear superstructures Shankar et al., 2003 Azadirachta indica Leaves Au3+ Ag+ Shankar et al., 2004 Leaves Ag+ 20-nm-size with nearly spherical shape Tripathy et al., 2010 Cinnammum camphora Leaves Au3+ 55 to 80 nm/triangular or spherical Huang et al., 2007

231©FORMATEX 2011


Cinnamon zeylanicum Bark Ag+ 31 and 40/Quasi-spherical and small, rod-shaped

Sathishkumar et al., 2009

Aloe vera Leaves Au3+ spherical Chandran et al., 2006 Aloe vera Pulp Ag+ 25/ spherical Zhang et al., 2010 Aloe vera Leaves In2O3 5-50 nm/ Maensiri et al., 2008 Eclipta Leaves AgNO3 - Jha et al., 2008 Eucalyptus camaldulensis Leaves Au 6–20 nm Haratifar et al., 2009 Cycas Leaves Ag+ 3.29 Jha and Prasad, 2009 Jatropha curcas Latex Ag+ - Bar et al., 2009a Cynnamon zeylanicum Bark Ag+ - Sathishkumar et al., 2009 Black Tea Leaves Au3+ Ag+ - Begum et al., 2009 Ipomoea aquatica, Enhydra fluctuans Ludwigia adscendens

Leaves 100 – 400 nm spherical and cubic

Roy and Barik, 2010

Desmodium triflorum Ag+ 5–20 nm/ spherical Ahmad et al., 2011 Murraya koenigii Leaves Ag+ 20 nm/ hexagonal and nearly spherical Philip et al., 2011a and b Citrus limon Ag+ - Prathna et al. 2011 Coriandrum sativum Leaves Ag+ 26 spherical Sathyavathi et al., 2010 Diopyros kaki Leaves Platinum 2 to 12 nm Song et al., 2010 Gliricidia sepium Leaves Ag+ 27 nm,/spherical Rajesh et al., 2009 Hibiscus rosa sinensis Leaves Ag+ Philip, 2010 Jatropha curcas seeds Ag+ 15 to 50 nm Bar et al., 2009b Capsicum annuum Leaves Ag+ 10-12 Li et al., 2007 Medicago sativa - Au 4–10 nm/fcc twinned, crystal and icosahedral Gardea-Torresdey et al., 2002 Helianthus annus, Basella alba, Oryza sativa, Saccharum officinarum, Sorghum bicolour, Zea mays

leaves Ag+ - Leela and Vivekanandan, 2008

Medicago sativa Leaves Gold fcc twinned, crystal and icosahedral 4–10 nm

Gardea-Torresdey et al., 2002

Medicago sativa Leaves Gold fcc tetrahedral, hexagonal platelets, icosahedral multiple twinned, decahedral multiple twined and irregular shaped- 15–200 nm

Singh et al., 2006

Chilopsis linearis Leaves Gold 1.1 nm Armendariz et al., 2004 Pelargonium graveolens Leaves Gold Spherical rods, flat, sheets and triangular 21–70 nm Zong et al., 2004 Hop biomass - Gold L’opeza et al., 2005 Cymbopogon flexuosus Leaves Gold Triangular, hexagonal Shankar et al., 2004; 2005

Avena sativa Leaves Gold fcc tetrahedral, decahedral, hexagonal, icosahedral multiple twinned, irregular shaped, rod shaped

Armendariz et al., 2004

Cicer arietinum Leaves Gold Triangular Ghule et al., 2006

Tamarindus indica Leaves Gold Triangular Ankamwar et al., 2005

Triticum aestivum Leaves Gold fcc tetrahedral, hexagonal platelets, irregular shaped, rod shaped, decahedral multiple twined, icosahedral multiple twined 10–30 nm

Armendariz et al., 2002; Gardea-Torresdey et al., 1999

Sesbania Leaves Gold Spherical, 6–20 nm Sharma et al., 2007 Medicago sativa Leaves Ag+ Spherical 2–20 nm Gardea-Torresdey et al., 2003 Quercetin Leaves Ag+ Radius 1–1.5 mm Egorova and Revina, 2000 Rice paper plant stem - Ag+ Below 100 nm Shankar et al., 2003

Aloe vera Leaves Silver and gold

Triangular, spherical Chandran et al., 2006

Emblica officinalis Leaves Silver, gold

10–20 nm, 15–25 nm Ankamwar et al., 2005

Azadirachta indica Leaves Ag+

gold

Ag core–Au shell Polydisperse, flat, plate-like, spherical, peculiar core–shell structure 5–35 nm diameter, 50–100 nm

Shankar et al., 2004

Cinnamommum camphora Leaves Silver and gold

Triangular, spherical 55–80 nm Huang et al., 2007

Capsicum annuum Leaves Silver - Gardea-Torresdey et al., 2005 Pelargoniumgraveolens Leaves Silver 16–40 nm Singaravelu et al., 2007

Brassica juncea Leaves Silver, gold, copper

- Haverkamp et al., 2007

- Informations are not available

232 ©FORMATEX 2011


A rapid reduction of the silver ions was observed when the silver nitrate solution was contacted with Pelargonium graveolens leaf extract (Shankar et al., 2003). Silver nanoparticles ranging from 55 to 80 nm in size and triangular or spherical gold nanoparticles were fabricated using the novel sundried biomass of Cinnammum camphora leaf (Huang et al., 2007). Eclipta (Asteraceae) is a common weed growing mostly in a shade area (Jha et al., 2008). Extract from Eclipta leaf has been used as medically, the plant is rich in flavonoids. Biosynthesis of silver nanoparticles was also conducted using Cycas leaf extract. Cycas (Cycadaceos) is a common gymnospermic plant and is a commercial source of sago (Jha and Prasad, 2009), having flavonoids broadly belonging to the class of phenolic compounds. Its AgNO3 based particle size ranged from 2-6 nm with average of 3.29 ± 0.22 nm. The XRD patter shows that the silver nanoparticles are crystalline in nature. Silver nanoparticles were successfully synthesized using the latex of Jatropha curcas (Bar et al., 2009a). The bark powder and water extract from Cynnamon zeylanicum tree were used for silver synthesis (Sathishkumar et al., 2009). The extract from Black Tea has been employed as a reducing agent for the synthesis of Au and Ag nanoparticles (Begum et al., 2009). Three different extracts were prepared from Black Tea: (i) tea leaf broth, (ii) ethyl acetate extract and (iii) CH2Cl2 extract. Metal nanoparticles were synthesized by adding aqueous solution of AgNO3 to any of the three extracts. The formation and growth of the nanoparticles was monitored with the help of absorption spectroscopy and transmission electron microscopy. Roy and Barik (2010) investigated the synthesis of silver nanoparticles from weeds namely, Ipomoea aquatica, Enhydra fluctuans and Ludwigia adscendens. The formation of silver nanoparticles as well as their morphological dimensions in the SEM study demonstrated that the average size was from 100–400 nm with inter-particle distance, where as the shapes were spherical and cubic in I. aquatica but only spherical in E. fluctuans and L. adscendens. Recently, in 2011 Ahmad and co-workers (Ahmad et al., 2011) reported single-step environmental friendly approach for the synthesis of silver nanoparticles using Desmodium triflorum. The biomolecules found in plants induce the reduction of Ag+ ions from silver nitrate to silver nanoparticles (AgNPs). Silver nanoparticles were synthesized using aqueous extract of Azadirachta indica leaves (Shankar et al., 2004; Tripathy et al., 2010). A facile bottom-up ‘green’ and rapid synthetic route using Murraya koenigii leaf extract as reducing and stabilizing agent was investigated for the production of silver nanoparticles at ambient conditions by Philip and his co-workers in 2011 (Philip et al., 2011a). The biosynthesized silver nanoparticles were approximately 10nm. Philip in 2011 reported rapid biosynthesis of well-dispersed silver nanoparticles by aqueous Mangifera indica leaf extract. At a pH of 8, the colloid consists of well-dispersed triangular, hexagonal and nearly spherical nanoparticles having size ~20 nm (Philip, 2011b). Silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon extract by Prathna et al. (2011). In addition to the plant extracts/broth, their bioactive principles have also been used for the biosynthesis. For instance Huang and co-workers (2010) used Bayberry tannin (BT), a natural plant polyphenol for one-step synthesis of gold nanoparticles in aqueous solution at room temperature.

4.2. Preparation of botanicals

Any plant of interest has been collected from the available sites, collected plant sample are washed thoroughly thrice with tap water to remove both epiphytes and necrotic plants; then once rinsed with sterile distilled water to remove any associated debris if any. These clean, fresh materials are shade-dried for two weeks, and powdered using domestic blender. For the plant broth preparation, ten gram of the dried powder is boiled with 100 mL of deionised distilled water (hot percolation method). The resulted infusion is filtered thoroughly until no insoluble material appeared in the broth.

4.3. Synthesis

Exactly 17 mg of AgNO3 is dissolved in 100 mL distilled water (10-3M). Ten mL of plant extract is added to 90 mL of 10-3M AgNo3 solution for reduction of Ag+ ions. The reduction of pure Ag+ ions is monitored by measuring the UV-vis spectra of the solution at regular intervals after diluting a small aliquot (0.2 mL) of the sample 20 times. UV-vis spectra were recorded as a function of time/temperature/concentration of reaction mixtures/pH etc. on a UV- spectrophotometer. More details about the characterization have been given in the forth coming section.

4.4. Characterization

Microscopic techniques such as scanning electron microscopy, transmission electron microscopy and atomic force microscopy are mainly used for morphological studies of nanoparticles. Before morphological studies, there is need to standardize the synthesis of nanoparticles using plants or their extracts. The formation of various nanoparticles from their different salts gives characteristic peaks at different absorptions that can be monitored using UV-vis spectroscopy. For example, silver nanoparticles formation from silver ions show an absorption peak around 450 nm, while gold nanoparticles show an absorption peak around 550 nm. Similarly, several other metal nanoparticles show characteristic absorption peaks. A progressive increase in the characteristic peak with increase in reaction time and concentration of plant extracts with salt ions is a clear indicator of nanoparticle formation. UV-vis absorption spectra show peaks characteristic of the surface plasmon resonance of nanosized particles (Armendariz et al., 2002; Gardea-Torresdey et al., 2002; 2003; Shankar et al., 2003; 2004; 2005; Amkamwar et al., 2005a; 2005b; L’opeza et al., 2005; Duran et al.,

233©FORMATEX 2011


2005; Ghule et al., 2006; Chandran et al., 2006; Rodriguez et al., 2007; Sharma et al., 2007; Huang et al., 2007; Haverkamp et al., 2007) (reference under Plants Ag and Au in table 1). The X-ray diffraction (XRD) technique is used to establish the metallic nature of particles. X-rays are electromagnetic radiation with typical photon energies in the range of 100 eV–100 keV. The energetic X-rays can penetrate deep into the materials and provide information about the bulk structure. However; Fourier transform infrared (FTIR) spectroscopy is a chemical analytical technique, which measures infrared intensity vs wavelength (wave number) of light. It is used to determine the nature of associated molecules of plants or their extracts with nanoparticles. This technique has been used in the characterization of silver and gold nanoparticles and their associated molecules from plant extracts in various studies (Armendariz et al., 2002; Gardea-Torresdey et al., 2002; 2003; Shankar et al., 2003; 2004; 2005; Amkamwar et al., 2005 a; 2005b; Duran et al., 2005; Chandran et al., 2006; L’opeza et al., 2005; Ghule et al., 2006; Huang et al., 2007; Rodriguez et al., 2007; Sharma et al., 2007; Haverkamp et al., 2007). Raman spectroscopy is conventionally performed with green, red or near-infrared lasers. These wavelengths are below the first electronic transitions of most molecules, as assumed by scattering theory. The situation changes if the wavelength of the exciting laser is within the electronic spectrum of a molecule. In that case, the intensity of some Raman-active vibrations increases by a factor of 102–104. This resonance enhancement or resonance Raman Effect can be quite useful. The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photo thermal therapeutic applications, is based on the optical properties of the nanoparticles. It has been described by the use of Mie theory and the discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica–gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties, viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions (Jain et al., 2006) Use of surface-enhanced Raman spectroscopy (SERS) in new material characterization, concept development and in identifying their applications has been thoroughly reviewed (Dieringer et al., 2006).

4.5. Size and shape

Various factors govern the size and shape of the bionano particles. For instance, reaction temperature (Rai et al., 2006) and concentrations of the leaf broth (Song et al., 2010), reaction time (Li et al., 2007); regarding the reason of decrease in particle size with temperature, we can hypothesize as follows. As the reaction temperature increases, the reaction rate increases and thus most silver ions are consumed in the formation of nuclei, stopping the secondary reduction process on the surface of the preformed nuclei (Song and Kim, 2009).

5.1. Applications of bionano particles: a general view

The use of gold nanoparticles dates back to the 16th century, for both medical and staining purposes. There after, gold nanoparticles have found application in analytical methods such as colorimetric techniques for the determination of heavy metal ions in aqueous solutions (Armendariz et al., 2002) Gold nanoparticles possess catalytic activity, and hence are used for reactions such as the water gas shift reaction and selective oxidation of CO (Andreeva, 2002; Hutchings and Haruta, 2005). Gold nanoparticles are also used in the field of sensors (Liu and Lu, 2004; Yanez-Sedeno and Pingarron, 2005). In biology, gold nanoparticles are used for the development of biosensors, DNA labels, (Groning et al., 2001; Tang et al., 2006) and in medicine (Paciotti et al., 2004). However, spherical gold nanoparticles have been used to generate functional electrical coatings (Singh et al., 2006). In medical applications, gold nanoparticles have been used in treating B-chronic lymphocytic leukemia (CLL). CLL is an incurable disease predominantly characterized by apoptosis resistance. Earlier CLL treatment was with anti-VEGF antibody; however, treatment was found to be more effective when VEGF antibody was attached to the gold nanoparticles. Apoptosis with gold–AbVF was higher than with the CLL cells exposed only to VEGF antibody or gold nanoparticles. Non-coated gold nanoparticles alone were able to induce some level of apoptosis in CLL B-cells. Thus gold nanoparticles could be used for treating CLL (Mukherjee et al., 2007) Gold nanoparticles have also been used in the Carter-Wallace home pregnancy test ‘First Response’. This uses conventional micrometer-sized latex particles in conjunction with gold nanoparticles (<50 nm diameter), which make them pink. The nanoparticles are derivatized with antibodies to human chorionic gonadotrophin, a hormone released by pregnant women. When mixed with a urine sample containing this hormone, the micro- and nanoparticles are co-agglutinated and the resulting clumps are colored pink (Bangs, 1996). The plasmon resonance absorption of colloidal gold particles has been exploited in a proposed DNA detection method (Elghanian, 1997). A unique, sensitive, and highly specific immunoassay system for antibodies using gold nanoparticles has been developed (Thanh and Rosenzweig, 2002). Crumbliss and co-workers have found that adsorption of redox enzymes to colloidal gold causes no loss of enzymatic activity. The enzyme-covered nanoparticles when electrodeposited onto platinum gauze or glassy carbon resulted in synthesis of enzyme electrodes (Crumbliss et al., 1992). Owing to the distinct biological activity of silver nanoparticles, they have found application in ecology and medicine. Silver nanoparticles showed good antimicrobial activity and therefore can be used for purification in water-filtering apparatus (Revina and Egorova, 1998). The interaction of metallic nanoparticles with biomolecules, microorganisms and viruses

234 ©FORMATEX 2011


is another expanding field of research. It was noticed that silver nanoparticles undergo a size-dependent interaction with HIV-1. Nanoparticles ranging in size from 1 to 10 nm readily interact with the HIV-1 virus via preferential binding to gp120 glycoprotein knobs. This specific interaction of silver nanoparticles inhibits the virus from binding to host cells, demonstrated by in vitro study. Hence, silver nanoparticles could find application in preventing as well as controlling HIV infection (Elechiguerra et al., 2005). Silver nanoparticles also find application in topical ointments and creams used to prevent infection of burns and open wounds (Becker, 1999). Another widely used application is in medical devices and implants prepared with silver-impregnated polymers. In addition, silver-containing consumer products such as colloidal silver gel and silver-embedded fabrics are now used in sporting equipment (Silver, 2003). Hydrophobic Ag–Au composite nanoparticles show strong adsorption and good electrical conducting properties, and therefore can be used in enzyme electrode design. Current response of the glucose biosensor in the presence of Ag–Au nanoparticles has been reported to be much higher than that without nanoparticles. These nanoparticles can assist electron transfer between the enzyme and the bulk electrode surface. In these composite particles, current response of electrodes with molar ratios silver (50)–gold (50) and silver (25)–gold (75) was higher than that with silver (75)–gold (25) molar ratio (Ren et al., 2005). Gold and silver nanoparticles have also found application in surfaced-enhanced Raman spectroscopy (SERS). Use of SERS surfaces prepared by self-assembly of gold and silver nanoparticles on glass and other substrates has shown a high degree of reproducibility (Freeman, 1995). A novel, direct, rapid, and label-free electrochemical immunoassay based on a core/shell Ag–Au nanoparticle monolayer as sensing interface has been developed for probing IgG.50 Use of such nanoparticles suggests that they may be explored in many more applications for human benefit.

5.2. Antimicrobials

Antimicrobial agents are so widespread that they are likely to play an important protective role. These agents have a variety of activities ranging from gram negative selective to gram positive selective to broad spectrum in nature. However it is important to measure MICs in the correct fashion since these agents tend to precipitate at high concentrations and bind to many surfaces. The best agents have good MICs against a wide range of bacteria, including some of the most difficult to treat, antibiotic-resistant pathogens. They are bactericidal with very rapid killing kinetics, even around the MIC. It is also very difficult to raise mutants resistant to these agents, and there are very few naturally resistant bacteria (none are major human infectious agents). As a result of their mechanism of action, some of the available agents have subsidiary activities that offer added side benefits, including an ability to neutralize endotoxin and synergy with conventional antibiotics especially against resistant mutants. For these reasons they appear to have excellent potential in the fight against antibiotic-resistant bacterial pathogens. Individual agents have also been shown to have a variety of interesting activities including antifungal, antiviral, antiparasitic, and anticancer activities and an ability to promote wound healing. In most cases the exact mechanisms behind these activities are not well understood. The mechanism of the bactericidal effect of silver and nanosilver remains to be in debate. Several studies propose that 1) Ag NPs may attach to the surface of the cell membrane disturbing permeability and respiration functions of the cell. Bactericidal activity depends upon the surface area of the particles. For instance smaller AgNPs having the large surface area available for interaction would give more bactericidal effect than the larger AgNPs 2) It is also possible that Ag NPs not only interact with the surface of membrane, but can also penetrate inside the bacteria 3) Ag NPs synthesized using disaccharides, maltose and lactose, have a higher antibacterial activity than those synthesized using monosaccharides, glucose and galactose and 4) SDS, Tween 80 has the capability to modify the antibacterial activity

5.3. Why metal nanoparticles?

By the above said reasons nanoparticles can be used as antimicrobicides. Moreover, nanoparticles show sharp prejudice from their bulk in many respects which becomes bonus for developing diagnostic tools and antimicrobials. Certain nanocrystals are attractive probes of biological markers because of: small size (1-100nm), large surface to volume ratio, chemically alterable physical properties, change in the chemical and physical properties with respect to size and shape, strong affinity to target particularly proteins, structural sturdiness in spite of atomic granularity, enhanced or delayed particles aggregation depending on the type of the surface modification, enhanced photoemission, high electrical and heat conductivity and improved surface catalytic activity (Liu, 2006; Garg et.al., 2008; McNeil, 2005; Rosi and Mirkin, 2005; Shrestha et.al., 2006)

5.4. Nano particles as microbicides

Silver nanoaparticles have important applications in the field of biology such as antibacterial agents and DNA sequencing. Silver has been known to exhibit strong toxicity to wide range of microorganisms. Antibacterial property of silver nanoparticles against St. aureus, Ps. aeruginosa and Es. coli has been investigated (Rai et al., 2009). Silver nanoparticles were found to be cytotoxic to E. coli. It was showed that the antibacterial activity of silver nanoparticles was size dependent. Silver nanoparticles mainly in the range of 1 -10 nm attach to the surface of cell membrane and drastically disturb its proper function like respiration and permeability (Morones et al., 2005). The fluorescent bacteria

235©FORMATEX 2011


were used to investigate the antibacterial properties of silver nanoparticles (Gogoi et al., 2006). The green fluorescent proteins (GFPs) were adapted to these studies. The general understanding is that silver nanoparticles get attached to sulfur containing proteins of bacteria cell causes the death of the bacteria. The fluorescent measurements of the cell-free supernatant reflected the effect of silver on recombination of bacteria. The silver nanoparticles were also used for impregnation of polymeric medical devices to increase their antibacterial activity. Silver impregnated medical devices like surgical masks and implantable devices showed significant antimicrobial efficiency (Furno et al., 2004). Silver nanoparticles synthesized by F. oxysporum strain incorporated in cotton cloth exhibition antibacterial activity against S. aureus (Marcato et al., 2005). The sterile cloth and materials are important in hospital, for example, where often wounds are contaminated with microorganisms, in particular fungi and bacteria, like S. aureus. Thus, to reduce or prevent infections, various antibacterial disinfections techniques have been developed for all types of textiles. Furthermore, silver nanoparticles can be exploited in medicine for burn treatment, dental materials, coating stainless steel materials, textile fabrics, water treatment, sunscreen lotions etc. (Duran et al., 2007). The high synergistic activity of silver nanoparticles and antibiotics was observed with erythromycin against St. aureus (Shahverdi et al., 2007). The antibacterial properties of the biosynthesized silver nanoparticles when incorporated on textile fabric were investigated (Kong and Jang 2008). There have been relatively few studies on the applicability of silver nanoparticles to control plant diseases. Kim et al. (2008), studied the antifungal effectiveness of colloidal nano silver (1.5 nm average diameter) solution, against rose powdery mildew caused by Sphaerotheca pannosa var. rosae. It is a very wide spread and common disease of both green house and outdoor grown roses. It causes leaf distortion, leaf curling, early defoliation and reduced flowering. The effects of silver nanoparticles were investigated for its antifungal activity against sclerotium-forming phytopathogens especially Rhizoctonia solani, Sclerotinia sclerotiorum and S. minor by Min and his co-workers in 2009 (Min et al., 2009). They found that the antimicrobial efficiency of the silver nanoparticles observed among the fungi on their hyphal growth in the following order, R. solani > S. sclerotiorum > S. minor. In particular, the sclerotial germination growth of S. sclerotiorum was most effectively inhibited at low concentrations of silver nanoparticles. A microscopic observation revealed that hyphae exposed to silver nanoparticles were severely damaged, resulting in the separation of layers of hyphal wall and collapse of hyphae. This study suggests the possibility to use silver nanoparticles as an alternative to pesticides for scleotium- forming phytopathogenic fungal controls. Jo et al. (2009) investigated various forms of silver ions and silver nanoparticles for their antifungal potency against two plant-pathogenic fungi, Bipolaris sorokiniana and Magnaporthe grisea an important pathogens on grasses. In vitro Petridish assays indicated that silver ions and nanoparticles had a significant effect on the colony formation of these two pathogens. Effective concentrations of the silver compounds inhibiting colony formation by 50% (EC50) were higher for B. sorokiniana than for M. grisea. The inhibitory effect on colony formation significantly diminished after silver cations were neutralized with chloride ions. Growth chamber inoculation assays further confirmed that both ionic and nanoparticle silver significantly reduced these two fungal diseases on perennial ryegrass, Lolium perenne. Aguilar-Me´ndez et al. (2010) synthesized colloidal silver nanoparticles by reducing silver nitrate solutions with glucose, in the presence of gelatin as capping agent. They evaluated the antifungal activity of the silver nanoparticles on the phytopathogen Colletotrichum gloesporioides, which causes anthracnose in a wide range of fruits, such as apple, avocado, mango, papaya, etc. Anthracnose lesions, for example in strawberry, develop as tan or light brown, circular, sunken lesions on ripe or ripening fruit. Generally, the symptoms become evident only during the post-harvest period. Anthracnose is controlled principally by application of synthetic fungicides during the post-harvest period (Muñoz et al., 2009). However, the indiscriminate use of them has caused the emergence of resistant strains. Also the residue levels of the chemicals may represent a serious problem to the human health (Gamagae et al., 2003). The use of metal nanoparticles as new antimicrobial agents could represent a viable alternative to delay or inhibit the growth of many pathogens species. The UV–Vis spectra indicated the formation of silver nanoparticles preferably spherical and of relatively small size (<20 nm). The above-mentioned was confirmed by TEM, observing a size distribution of 5–24 nm. They reported that the growth of C. gloesporioides in the presence of silver nanoparticles was significantly delayed in a dose dependent manner. Though enormous information’s were available about the antimicrobial activity of various terrestrial plants, none has studies about the antimicrobial activity of cultivatable plants. For the first time Govindaraju et al.(2010) studied the antimicrobial activity of Solanum torvum mediated silver nanoparticles against pathogenic bacteriae and fungi of silkworm Bombyx mori such as Ps. aeruginosa, St. aureus, Aspergillus flavus and As. niger using agar well diffusion method. The results confirmed that growth of St. aureus has been arrested by the S. torvum bionano particles. Very recently Linga Rao and Savithramma (2011) recorded the antimicrobial activity of nano-based leaf extract of Svensonia hyderabadensis against A. niger, Fu. oxysporum, Curvularia lunata and Rhizopus arrhizus. Results showed that the bionano particle has both antibacterial and antifungal activity.

5.5. Bioassays used

So far the following methods have been followed to evaluate the antimicrobial activity of bio-nano particles (Table 2 and 3).

236 ©FORMATEX 2011


Table 2. Antimicrobial activities of bionanoparticles synthesized using silver with botanicals

Biological entity Test microorganisms Method Impact Reference

Argimone mexicana Escherichia coli and Pseudomonas aeruginosa; Aspergillus flavus

Disk diffusion for bacteria and food poisoning for fungi

Highly active against test pathogens

Khandelwal et al., 2010

Aloe Vera E. coli Standard plate count 200 μmolL-1 caused 100% inhibition of bacterial growth

Zhang et al., 2010

Caulerpa scalpelliformis

Xanthomonas campestris pv. malvacearum

MIC determination using INT method

MIC was found to be 23.34 µg/mL

Present observation

Caulerpa veravalensis

X. campestris pv. malvacearum


MIC was found to be 30 µg/mL

Present observation

Desmodium triflorom Staphylococcus sp., E. coli, Bacillus subtilis

MIC determination Highly active (27µg/mL for E. coli)

Ahmad et al., 2011

Cinnamon zeylanicum

E. coli BL-21 Growth curve determination

EC50 value 11±1.72 mg/L.

Sathishkumar et al., 2009

Gliricidia sepium S. aureus, E. coli, P. aeruginosa and Klebsiella pneumoniae

Agar well diffusion Highly activie against S. aureus

Rajesh et al., 2009

Ocimum sanctum & Vitex negundo

S. aureus, Vibrio cholerae, Proteus vulgaris and P. aeruginosa.

Agar well diffusion Active against P. aeruginosa (6-36mm)

Prabhu et al., 2010

Padina pavonica X. campestris pv. malvacearum


MIC was found to be 60 µg/mL

Present observation

Sagassum wightii S. aureus, B. rhizoids, E. coli, P. aeruginosa

Agar well diffusion highly effective against test microbes

Govindaraju et al., 2008

Vernonia cinerea X.campestris pv. malvacearum


MIC was found to be 80µg/mL

Present observation

Trianthema decandra E. coli and P. aeruginosa

Disk diffusion technique

highly effective against test microbes

Geethalakshmi and Sarada, 2010

Solanus torvum P. aeruginosa, S. aureus, A. flavus and Aspergillus niger


Highly active against Staphylococcus aureus

Govindaraju et al., 2010

Svensonia hyderabadensis

A.niger, Fusarium oxysporum, Curvularia lunata and Rhizopus arrhizus


Antibacterial and antifungal activity

Linga Rao and Savithramma, 2011

Table 3. Antimicrobial activities of bionanoparticles synthesized using silver with various microbes

Biological entity Test microorganisms Method Impact Reference

Amylomyces rouxii KSU-09

Shigella dysenteriae typeI, Staphylococcus aureus, Citrobacter sp., Escheeichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans and Fusarium oxysporum

Agar well diffusion

Highly active against test microorganisms

Musarrat et al.,2010

Alternaria alternata Phoma glomerata, P.herbarum, F. semitectum, Trichoderma sp. and C.albicans


Combination with flucanazole increased the antifungal activity against C. albicans, Trichoderma sp. and P. glomerata.

Gajbhiye et al., 2009

Aspergillus sp. Staphylococcus sp. Agar well diffusion

13-19mm Saravanan, 2010

Euphorbia hirta S. aureus, E .coli, K. pneumoniae, B. cereus and P. aeruginosa

Agar well diffusion

SS effective against B.cereus and S.aureus

Elumalai et al., 2010

Klebsiella pneumoniae

S. aureus, E. coli


Penicillin G, amoxicillin, erythromycin, clindamycin, and vancomycin increased in the Presence of nanoparticles

Shahverdi et al., 2007

Fusarium acuminatum

S. aureus, Salmonella typhi, Staphylococcus epidermidis, and E. coli


Antibacterial activity Avinash et al. 2008

237©FORMATEX 2011


Phytophthora infestans

E. coli, S. typhi, K. pneumoniae, P. vulgaris, B. subtilis, and S. aureus

Minimum Inhibition Concentrations (MIC)

MIC was found to be 5 mg/ml

Thirumurugan et al., 2009

Trichoderma viridae S. typhi, E, coli, S. aureus, and Micrococcus luteus


Ampicillin, kanamycin, erythromycin, and chloramphenicol increased in the presence of nanoparticles

Fayaz et al., 2009

5.5.1. Agar well diffusion method

The antibacterial activity of biosilver nanoparticles was tested by standard agar well diffusion method. Wells were made using sterile cork borer under aseptic condition. The inocula were prepared by diluting the overnight cultures with 0.9% NaCl to a 0.5 McFarland standard and were swabbed onto the plate. Different concentrations of the nanoparticles were loaded on marked wells with the help of micropipette under aseptic conditions and plates were incubated at 37ºC for 24 hrs. The zone of inhibition was measured using a ruler and expressed in mm (Prabhu et al., 2010).

5.5.2. Agar disk diffusion method

The antibacterial assays were tested by standard agar disc diffusion method. Fresh overnight cultures of inoculum in Luria Bertani broth (100 μl) of each culture diluted to 0.5 McFarland standard was spread onto LB agar plates. Sterile paper discs of 3mm diameter along with standard antibiotic (positive control) containing discs were placed in each plate. The plates were incubated at 37ºC for 24 hrs. The zone of inhibition was measured using a ruler and expressed in mm (Khandelwal et al., 2010).

5.5.3. Determination of bacterial growth kinetics

To test the bactericidal activity of the silver nanoparticles produced, growth inhibition studies (Sathishkumar et al., 2009) were conducted in Luria–Bertani (LB) brothmedia. For growth inhibition studies, sterile 250mL Erlenmeyer flasks, each containing 100mL LB broth media and the desired amount of Ag nanoparticles, were inoculated with 1mL of the freshly prepared bacterial suspension in order to maintain initial bacterial concentration in the same range in all the flasks. The flasks were then incubated in a rotary shaker at 160rpm at 37◦C. Bacterial growth was then monitored every hour for 24 h by measuring the increase in absorbance at 600 nm in a spectrophotometer. The experiments also included a control flask containing only media and bacteria devoid of Ag nanoparticles. The data derived from the above experiments were used to estimate the EC50 using Sigma plot software.

5.5.4. Determination of Minimum Inhibitory Concentration (MIC)

Broth microdilution assay was used to determine the MIC (Eloff, 1998). Test sample (75 µl) of various concentrations was added into sterile microtitre plates. Bacterial cell suspension (75 µl) corresponding to 1 × 108 CFU/ml was added in all wells except those in control well. Control well consisted of sterile distilled water andMueller Hinton (MH) broth to check sterility while those in negative control well were filled with MH broth and bacterial suspension to check for adequacy of the broth to support bacteria growth. The plates placed in sterile Petri plate (14 cm) and incubated at 37°C for 24 hrs. To indicate bacterial growth, 40µl of 0.2 mg/ml P-Iodonitroterazolium chloride (HiMedia) was added to each well and incubated for another 30 min. The colourless tetrazolium salt acts as an electron acceptor and is reduced to a red-coloured formazan product by biologically active organisms. Inhibition of bacterial growth was visible as a clear colourless well and the presence of growth was detected by the presence of pink-red color. The lowest concentration showing no colour change was considered as the MIC.

5.5.5. Colony count method

The standard Colony Forming Unit (CFU) on the agar plates was applied to test the antibacterial activity. The test bacterial suspensions of 103 (100 µl) was spread onto the agar medium with different concentrations of silver nanoparticles under aseptic condition and incubated at 37°C for 24 hrs. After incubation the numbers of colonies formed were counted. The percentage reduction ratio, of the bacteria for antibacterial evaluation has been expressed as,

R= A-B/A x 100% where R is the percentage reduction ratio, A - the number of bacterial colonies in Petri plates without silver nanoparticles and B - the number of colonies in Petri plates with silver nanoparticles (Zhang et al., 2010).

5.5.6. Food Poisoning Method

The antifungal assays were performed by food poisoning method. Potato dextrose agar (PDA) medium was used in the study. The plates containing medium with different concentrations of silver nano particles were inoculated each alone at

238 ©FORMATEX 2011


the centre with 5mm inoculum disc of pathogenic fungus and incubated at 25°C for 7 days. The medium with inoculum disc of each fungus but without silver nano particles served as control. After 7 days of incubation the mycelial growth were measured using ruler and expressed in mm (Khandelwal et al., 2010).

5.6. Mechanism of silver nanoparticles on bacteria

The mechanisms behind the activity of nano silver on bacteria are not yet fully elucidated, the three most common mechanisms of toxicity proposed up to now are: 1) uptake of free silver ions followed by disruption of ATP production and DNA replication, 2) formation of Reactive Oxygen Species (ROS) and 3) direct damage to cell membranes.

5.6. 1. Uptake of free silver ions

Antimicrobial properties of ionic silver are well known; thus, it is likely that eluted ions from silver nanoparticles are accountable for at least a part of their antibacterial properties. At sub-micromolar concentrations, Ag+ interacts with enzymes of the respiratory chain such as NADH dehydrogenase ensuing in the uncoupling of respiration from ATP synthesis. Ionic silver also binds with transport protein leading to proton leakage, inducing collapse of the proton motive force (Dibrov et al., 2002; Holt and Bard, 2005; Lok et al., 2006). Ionic silver hampers the uptake of phosphate and thus causes the efflux of intracellular phosphate (Schreurs and Rosenberg, 1982). The interaction with respiratory and transport proteins is due to the high affinity of Ag+ with thiol groups present in the cysteine residues of those proteins (Holt and Bard, 2005; Liau et al., 1997; Petering, 1976). In addition, it has been reported that Ag+ increases DNA mutation frequencies during polymerase chain reactions (Yang et al., 2009). Bacterial cells exposed to milli-molar Ag+ Doses suffer morphological changes such as DNA condensation and localization in an electron-light region in the center of the cell, cytoplasm contraction and disintegration of cell wall membrane, and cell membrane degradation allowing leakage of intracellular contents (Feng et al., 2000; Jung et al., 2008). Physiological changes take place together with the morphological changes. Bacterial cells enter a lively, but non-culturable state in which physiological levels can be measured but bacteria are not able to growth and replicate.

5.6. 2. Formation of Reactive Oxygen Species (ROS)

Reactive oxygen species (ROS) are likely natural by-products of the metabolism of respiring organisms. While small levels can be guarded by the antioxidant defenses of the cells such glutathione/glutathione disulfide (GSH/GSSG) ratio, excess ROS production may produce oxidative stress (Nel et al., 2006). The additional generation of free radicals can assault membrane lipids and lead to a breakdown of membrane and mitochondrial function or cause DNA damage (Mendis et al., 2005). Metals can act as catalysts and generate ROS in the presence of dissolved oxygen (Stohs and Bagchi, 1995). In this context, silver nanoparticles may catalyze reactions with oxygen directing to excess free radical generation. Studies performed in eukaryotic cells suggest that silver nanoparticles inhibit the antioxidant defense by interacting directly with GSH, binding GSH reductase or other GSH maintenance enzymes (Carlson et al., 2008). This could minimize the GSH/GSSG ratio and, subsequently, accumulate ROS in the cell. In bacterial cells, silver ions would likely induce the generation of ROS by abrogating the respiratory chain enzymes through direct interactions with thiol groups in these enzymes or the superoxide radical scavenging enzymes such as superoxide dismutases (Park et al., 2009). Kim et al. determined the presence of free radicals from silver nanoparticles by means of spin resonance measurements (Kim et al., 2007). They observed that silver nanoparticles and silver nitrate toxicity was eliminated in the presence of an antioxidant, these results leaded them to confer that the antimicrobial mechanisms of silver nanoparticles against S. aureus and E. coli was related to the formation of free radicals from the surface of silver nanoparticles and subsequent free radical induced membrane damage. 5.6. 3. Direct damage to cell membranes Nano silver interact with the bacterial membrane and are capable to penetrate inside the cell. TEM studies show that silver nanoparticles adhere to and penetrate into E. coli cells and also are able to induce the development of small pits in the cell membrane (Sondi and Salopek-Sondi, 2004; Choi et al., 2008; Raffi et al., 2008). Silver nanoparticles have been observed within E. coli cells at sizes much smaller than the original particles; moreover, silver nanoparticles with oxidized surfaces induce the formation of huge holes in E. coli surfaces after the interaction and large portion of the cellular content seemed to be ‘‘eaten away’’ (Smetana et al., 2008). The detailed mechanism by which silver nanoparticles interact with cytoplasmic membranes and are able to penetrate inside cells is not fully determined. One hypothesis expains that the interaction between nanoparticles and bacterial cells are due to electrostatic attraction between negatively charged cell membranes and positively charged nanoparticles (Raffi et al., 2008). However, this mechanism does not likely explain the adhesion and uptake of negatively charged silver nanoparticles. It has been also proposed that the preferential sites of interaction for silver nanoparticles and membrane cells might be sulfur containing proteins—in a similar way as silver interacts with thiol groups of respiratory chain proteins and transport proteins, interfering with their proper function (Morones et al., 2005). Despite the mechanism of interaction involved, it is evident that silver nanoparticles attached to bacterial cell membranes increase permeability and disturb respiration. Proteomic data show the accumulation of envelope protein precursors in E. coli

239©FORMATEX 2011


cells after exposure to silver nanoparticles (Lok et al., 2006). Energy from ATP and proton motive force is required in order to newly synthesize envelope proteins to be translocated to the membrane, therefore cytoplasmic accumulation of protein precursors suggests dissipation of proton motive force and depletion of intracellular levels of ATP. One of research subject focused on the measurement of biological binding signal between antigen and antibody using the triangular Ag-nanoparticles (Zhu et al., 2009). For biological applications, quantum dots and nanoparticles are conjugated with biospecific molecules such as antibodies, DNA, or enzymes. Most of these applications are based on the specific optical properties of gold or silver (Huo, 2007).

6. Future perspectives

During the past two decades, the interaction of a variety of plant, bacteria, fungi, actinomycetes and algae in the synthesis of silver nanoparticles have been well investigated. Plants, fungi and bacteria have huge potential for the production of silver nanoparticles; however, the previous studies are still largely in the discovery phase. Given the anticipated wide application of silver nanoparticles for commercial applications, in the field of agriculture applications using bacteria/ cyanobacteria/algae/plant that minimizes hazard and waste will be essential for the transition of nanoscience discoveries to commercial products of nanotechnology. Future work should implement systematic experiments which include development of silver nanoparticles of well-defined size and shape. Better understanding of the mechanisms of silver biosynthesis will enable us to achieve better control over size, shape, and monodispersity which will lead to the development of high precision in the production level and the application of nanoparticles for commercial scale agricultural applications in the management of plant disease.

7. Conclusion

The biological agents in the form of algae, plants and microbes have emerged as an efficient candidate for the synthesis of nanoparticles. These biogenic nanoparticles are cost efficient, simpler to synthesize, and focus toward a greener approach. But the exact mechanism of synthesis of biogenic nanoparticles needs to be worked out. Silver nano materials exhibit broad spectrum biocidal activity toward bacteria, fungi, viruses, and algae. This motivates its use in agricultural applications. However, if the amount of nano-scaled silver entering sewage becomes higher than the tolerable levels for microbial communities in wastewater treatment plants, critical environmental infrastructure might be impacted. Further, there is mounting evidence that silver nanoparticles exhibit an array of cytotoxic and genotoxic effects in higher organisms. This raises concern about possible impacts to higher organisms including humans. Although significant progress has been made to elucidate the mechanisms of silver nano material toxicity, further research is required to fully understand the processes involved and to safely exploit the tremendous antimicrobial properties of silver without jeopardizing human health, critical infrastructure, and the environment. Future in vivo, in vitro, and environmental studies should consider more systematically the various effects of aquatic chemistry on nano-scaled silver fate, transport, and toxicity.

Acknowledgement We are thankful to the authorities of St. Xavier’s college, Palayamkottai for the facilities and encouragement. We also extend our sincere thanks to Ministry of Earth Sciences, Govt. of India (MRDF/01/33/P/07) for the finical assistance of Bio-Nano particle synthesis

8. References

[1] Aguilar-Méndez, A.M., Martıń-Martıńez, E.S., Ortega-Arroyo, L., Cobiań-Portillo, G. and Sańchez-Espıńdola, E. 2010. Synthesis and characterization of silver nanoparticles: effect on phytopathogen Colletotrichum gloesporioides. J Nanopart Res. 13: 2525 – 32.

[2] Ahmad, A., Senapati, S., Khan, M.I., Kumar, R. and Sastry, M. 2005. Extra-/ intracellular, biosynthesis of gold nanoparticles by an alkalotolerant fungus, Trichothecium. J. Biomed. Nanotechnol., 1: 47-53.

[3] Ahmad, N., Sharma, S., Singh, V.N., Shamsi, S.F., Fatma, A. and Mehta, B.R. 2011. Biosynthesis of Silver Nanoparticles from Desmodium triflorum: A Novel Approach Towards Weed Utilization. Biotechnology Research International, 1-8.

[4] Ahmad, R.S., Sara, M., Hamid, R.S., Hossein, J. and Ashraf-Asadat, N. 2007. Rapid synthesis of silver nanoparticles using culture supernatants of Enterobacteria: A novel biological approach. Process Biochem., 42: 919-923.

[5] Andreeva, D. 2002. Low temperaturewater gas shift over gold catalysts. Gold Bull 35: 82–88. [6] Ankamwar, B., Chaudhary, M. and Sastry, M. 2005a. Gold nanotriangles biologically synthesized using tamarind leaf extract and potential

application in vapor sensing. Synth React Inorg Metal-Org Nano- Metal Chem., 35: 19–26. [7] Ankamwar, B., Damle, C., Ahmad, A. and Sastry, M. 2005b. Biosynthesis of gold and silver nanoparticles using Emblica officinalis fruit extract,

their phase transfer and transmetallation in an organic solution. J nanosci Nanotechnol., 5: 1665–1671. [8] Armendariz, V., Gardea-Torresdey, J.L., Jose-Yacaman, M., Gonzalez, J., Herrera, I. and Parsons, J.G. Gold nanoparticles formation by oat and

wheat biomasses, in Proceedings –Waste Research Technology Conference at the Kansas City, Mariott-Country Club Plaza July30–Aug1 (2002). [9] Armendariz, V., Herrera, I., Peralta-Videa, J., Jose-Yacaman, M., Troiani, H. and Santiago, P. 2004. Size controlled gold nanoparticle formation

by Avena sativa biomass: use of plants in nanobiotechnology. J Nanopart Res 6: 377–382. [10] Atiyeh, B.S., Costagliola, M., Hayek, S.N. and Dibo, S.A. 2007. Effect of silver on burn wound infection control and healing: review of the

literature. Burns, 33:139–148. [11] Avinash, I., Aniket; G., Sebastien, P., Carsten, S. and Mahendra, R. 2008. Mycosynthesis of Silver Nanoparticles Using the Fungus Fusarium

acuminatum and its Activity Against Some Human Pathogenic Bacteria. Current Nano Science. 4 (2): 141-144.

240 ©FORMATEX 2011


[12] Balaji, S.D., Basavaraja, S., Deshpande, R., Mahesh, B.D., Prabhakar, K.B. and Venkataraman, A. 2009. Extracellular biosynthesis of functionalized silver nanoparticles by strains of Cladosporium cladosporioides fungus. Colloids Surfaces B: Biointerfaces, 68: 88-92.

[13] Bangs, L.B. 1996. New developments in particle-based immunoassays: introduction. Pure Appl Chem 68:1873–1879. [14] Bar, H., Bhui, D.K., Sahoo, G.P., Sarkar, P., De, S.P. and Misra, A. 2009a. Green synthesis of silver nanoparticles using latex of Jatropha

curcas. Colloids Surf A: Physicochem Eng Asp, 339: 134–139. [15] Bar, H., Bhui, D.K., Sahoo, G.P., Sarkar, P., Pyne, S. and Misra, A. 2009b. Green synthesis of silver nanoparticles using seed extract of Jatropha

curcas. Colloids Surf A: Physicochem Eng Asp, 348: 212–216. [16] Basavaraja, S., Balaji, S.D., Lagashetty, A., Rajasab, A.H. and Venkataraman, A. 2007. Extracellular biosynthesis of silver nanoparticles using

the fungus Fusarium semitectum. Mater Res Bull, 43(5): 1164–1170. [17] Bazylinski, A.B. and Frankel, B.R. 2004. Magnetosome formation in Procayotes, Nature reviews – Microbiology, 2: 213-230. [18] Becker, R.O. 1999. Silver ions in the treatment of local infections. Met BasedDrugs, 6: 297–300. [19] Begum, A.N., Mondal, S., Basu, S., Laskar, A.R. and Mandal, D. 2009. Biogenic synthesis of Au and Ag nanoparticles using aqueous solutions

of Black Tea leaf extracts, Colloids Surfaces B. Biointerfaces, 71: 113-118. [20] Beveridge, T. J. and Murray, R.G.E. 1980. Sites of metal deposition in the cell wall of Bacillus subtilis. J. Bacteriol., 141: 876-887. [21] Bhainsa, C.K. and D’Souza, F.S. 2006. Extracellular biosynthesis of silver nanoparticles using the fungus Aspergillus funigatus. Colloids

Surfaces B; Biointerfaces, 47: 160-164. [22] Carlson, C., Hussain, S.M., Schrand, A.M., Braydich-Stolle, L.K., Hess, K.L., Jones, R.L. and Schlager, J.J. 2008. Unique cellular interaction of

silver nanoparticles: size-dependent generation of reactive oxygen species. J Phys Chem B, 112: 13608–13619. [23] Chandran, P.S., Chaudhary, M., Pasricha, R., Ahmad, A. and Sastry, M. 2006. Synthesis of gold nanotriangles and silver nanoparticles using

Aloe vera plant extract, Biotechnology Prog., 22: 577-583. [24] Choi, O., Deng, K., Kim, N., Ross, L., Surampalli, R. and Hu, Z. 2008. The inhibitory effects of silver nanoparticles, silver ions, and silver

chloride colloids on microbial growth. Water Res, 42: 3066–3074. [25] Chu, C.S., McManus, A.T., Pruitt, B.A. and Mason, A.D. 1988. Therapeutic effects of silver nylon dressing with weak direct current on

Pseudomonas aeruginosa infected burn wounds. J Trauma, 28: 1488–1492. [26] Crumbliss, A.L., Perine, S.C., Stonehuerner, J., Tubergen, K.R., Zhao, J. and Henkens, RW. 1992. Colloidal gold as abiocompatible

immobilization matrix suitable for the fabrication of enzyme electrodes by electrodeposition. Biotechnol Bioeng., 40: 483–490. [27] Culity, B.D. 1978. Elements of X-ray Diffraction, 2nd edn, Edison-Wesley Publishing Company Inc, USA. [28] Deitch, E.A., Marin, A., Malakanov, V. and Albright, J.A. 1987. Silver nylon cloth: in vivo and in vitro evaluation of antimicrobial activity. J

Trauma, 27: 301–304. [29] Dibrov, P., Dzioba, J., Gosink, K. and Hase, C. 2002. Chemiosmotic mechanism of antimicrobial activity of Ag? in Vibrio cholerae. Antimicrob

Agents Chemother, 46: 2668–2670. [30] Dieringer, J.A., McFarland, A.D., Shah, N.C., Stuart, D.A., Whitney, A.V. and Yonzon, C.R. 2006. Surface enhanced Raman spectroscopy: new

materials, concepts, characterization tools, and applications. Faraday Discuss 132:9–26. [31] Duran, N., Marcato, P.D., Alves, O.L., De Souza, G.I.H. and Esposito, E. 2005. Mechanistic aspects of biosynthesis of silver nanoparticles by

several Fusarium oxysporum strains. JNanobiotechnol., 3: 8–14. [32] Duran, N., Marcato, D.P., De Souza, H.I., Alves, L.O. and Espsito, E. 2007. Antibacterial effect of silver nanoparticles produced by fungal

process on textile fabrics and their effluent treatment, J. Biomedical Nanotechnology, 3: 203-208. [33] Egorova, E.M. and Revina, A.A. 2000. Synthesis of metallic nanoparticles in reverse micelles in the presence of quercetin. Colloids Surf A:

Physicochem Eng Asp 168: 87–96. [34] Elechiguerra, J.L., Burt, J.L., Morones, J.R., Camacho-Bragado, A., Gao, X. and Lara, H.H. 2005. Interaction of silver nanoparticles with HIV-1.

J Nanobiotechnol, 3: 6. [35] Elghanian, R., Storhoff, J.J., Mucic, R.C., Letsinger, R.L. and Mirkin, C.A. 1997. Selective colorimetric detection of polynucleotides based on

the distance-dependent optical properties of gold nanoparticles. Science, 277: 1078–1081. [36] Eloff, J.N. 1998. A sensitive and quick microplate method to determine the minimal inhibitory concentration of plant extracts for bacteria. Planta

Medica. 64: 711-713. [37] Elumalai, E.K., Prasad, T.N.V.K.V., Hemachandran, J., Therasa, S.V., Thirumalai, T. and David, E. 2010. Extracellular synthesis of silver

nanoparticles using leaves of Euphorbia hirta and their antibacterial activities. J. Pharm. Sci. & Res., 2(9): 549-554. [38] Fayaz, A.M., Balaji, K., Girilal, M., Yadav, R., Kalaichelvan, P.T. and Venketesan, R. 2010. Biogenic synthesis of silver nanoparticles and their

synergistic effect with antibiotics: a study against gram-positive and gram-negative bacteria. Nanomedicine: Nanotechnology, Biology and Medicine, 6(1):103-109.

[39] Feng, Q., Wu, J., Chen, G., Cui, F., Kim, T. and Kim, J. 2000. A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus. J Biomed Mater Res., 52: 662–668.

[40] Feynman, R. 1959. Lecture at the California Institute of Technology, December 29 [41] Freeman, R.G., Grabar, K.C., Allison, K.J., Bright, R.M., Davis, J.A. and Guthrie AP. 1995. Self-assembled metal colloid monolayers: an

approach to SERS substrates. Science, 267:1629–1632. [42] Fu, J.K., Liu, Y.Y., Fu, J.Y., Li, X.Q., Gu, P.Y. and Chen, P. 2000. Preparation of supported palladium catalyst by biochemical method. J.

Xiamen Univ. Nat. Sci., 39: 67-71. [43] Furno, F., Morley, K.S., Wong, B., Sharp, B.L. and Howdle, S.M. 2004. Silver nanoparticles and polymeric medical devices: a new approach to

prevention of infection. J. Antimicrob. Chemother., 54: 1019-1024. [44] Gajbhiye, M., Kesharwani, J., Ingle, A., Gade, A. and Rai, M. 2009. Fungus-mediated synthesis of silver nanoparticles and their activity against

pathogenic fungi in combination with fluconazole. Nanomed Nanotechnol Biol Med, 5: 382–386. [45] Gamagae, S.U., Sivakumar, D., Wijeratnam, R.S.W. and Wijesundera, R.L.C. 2003. Use of sodium bicarbonate and Candida oleophila to control

anthracnose in papaya during storage. Crop Prot, 22: 775–779. [46] Gardea-Torresdey, J.L., Tiemann, K.J., Gamez, G., Dokken, K., Tehuacanero, S. and Jos´e-Yacam´an, M. 1999. Gold nanoparticles obtained by

bio precipitation from gold (III) solutions. J Nanopart Res 1:397–404. [47] Gardea-Torresdey, J.L., Gomez, E., Peralta-Videa, J.R., Parsons, J.G., Troiani, H. and Jose-Yacaman, M. 2003. Alfalfa sprouts: a natural source

for the synthesis of silver nanoparticles. Langmuir 19:1357–1361. [48] Gardea-Torresdey, J.L., Parsons, J.G., Gomez, E., Peralta-Videa, J., Troiani, H.E. and Santiago, P. 2002. Formation and growth of Au

nanoparticles inside live alfalfa plants. Am Chem Soc., 2: 397–401. [49] Garg, J., Poudel, B. and Chiesa, M. 2008. Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid. J

Appl Phys, 103: 074301. [50] Geethalakshmi, R. and Sarada, D.V.L. 2010. Synthesis of plant-mediated silver nanoparticles using Trianthema decandra extract and evaluation

of their anti microbial activities. International Journal of Engineering Science and Technology, 2(5): 970-975. [51] Ghule, K., Ghule, A.V., Liu, J.Y. and Ling, Y.C. 2006. Microscale size triangular gold prisms synthesized using Bengal gram beans (Cicer

arietinum L.) extract and HAuCl4 × 3H2O: a green biogenic approach. J Nanosci Nanotechnol, 6: 3746–3751.

241©FORMATEX 2011


[52] Gogoi, K.S., Gopina, P., Paul, A., Ramesh, A., Ghosh, S.S. and Chattopadhyay, A. 2006. Green fluorescent protein expressing Escherichia coli as a model system for investigating the antimicrobial activities of silver nanoparticles, Langmuir, 22: 9322-9328.

[53] Gong, J., Liang, Y., Huang, Y., Chen, J., Jiang, J., Shen, G. and Yu, R. 2007. Ag/SiO2 core-shell nanoparticle-based surface-enhanced Raman probes for immunoassay of cancer marker using silica-coated magnetic nanoparticles as separation tools. Biosensors and Bioelectronics, 22: 1501–1507.

[54] Govindaraju, K., Khaleel Basha, S., Ganesh Kumar, V. and Singaravelu, G. 2008. Silver, gold and bimetallic nanoparticles production using single cell protein (Spirulina platensis) Geitler. Journal of MaterialsScience, 43: 5115-5122.

[55] Govindaraju, K., Tamilselvan, S., Kiruthiga, V. and Singaravelu, G. 2010. Biogenic silver nanoparticles by Solanum torvum and their promising antimicrobial activity. Journal of Biopesticides, 3(1): 394-399.

[56] Groning, R., Breitkreutz, J., Baroth, V. and Muller, R.S. 2001. Nanoparticles in plant extracts: factors which influence the formation of nanoparticles in black tea infusions. Pharmazie, 56: 790–792.

[57] Gurunathan, S., Kalishwaralal, K., Vaidyanathan, R., Venkataraman, D., Pandian, S.R.K., Muniyandi, J., Hariharan, N. and Eom, S.H. 2009. Biosynthesis, purification and characterization of silver nanoparticles using Escherichia coli. Colloids Surf B, 74(1): 328–335.

[58] Haratifar, E., Shahverdi, H.R., Shakibaie, M., Moghaddam, K.M., Amini, M. Montazeri, H. and Shahv, A.R. 2009. Semi-Biosynthesis of Magnetite-Gold Composite Nanoparticles Using an Ethanol Extract of Eucalyptus camaldulensis and Study of the Surface Chemistry. Journal of Nanomaterials, doi:10.1155/2009/962021

[59] Haverkamp, R.G., Marshall, A.T. and Van Agterveld, D. 2007. Pick your carats: nanoparticles of gold–silver–copper alloy produced in-vivo. J Nanopart Res., 9: 697–700.

[60] Holmes, J.D., Smith, P.R., Evans-Gowing, R., Richardson, D.J., Russell, D.A. and Sodeau, J.R. 1995. Energy-dispersive-X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes. Arch. Microbiol., 163: 143-147.

[61] Holt, K. and Bard, A. 2005. Interaction of silver(I) ions with the respiratory chain of Escherichia coli: an electrochemical and scanning electrochemical microscopy study of the antimicrobial mechanism of micromolar Ag. Biochemistry, 44: 13214–13223.

[62] Huang, J., Li, Q., Sun, D., Lu, Y., Su, Y., Yang, X., Wang, H., Wang, Y., Shao, W., He, N., Hong, J. and Chen, C. 2007. Biosynthesis of silver and gold nanoparticles by novel sundried Cinnamomum camphora leaf. Nanotechnology, 18: 105104-105114.

[63] Huang, X., Wu, H., Liao, X. and Shi, B. 2010. One-step, size-controlled synthesis of gold nanoparticles at room temperature using plant tannin. Green Chem., 12: 395 – 399.

[64] Huo, Q. 2007. A perspective on bioconjugated nanoparticles and quantum dots, ColloidsSurfaces B: Biointerfaces, 59: 1 -10. [65] Hutchings, G.J. and Haruta, M. 2005. A golden age of catalysis: a perspective. Appl Catal A, 291: 2–5. [66] Jain, P.K., Lee, K.S., El-Sayed, I.H. and El-Sayed, M.A. 2006. Calculated absorption and scattering properties of gold nanoparticles of different

size, shape, and composition: applications in biological imaging and biomedicine. J Phys Chem B., 110: 7238–7248. [67] Jha, K.A., Prasad, Kumar, V. and Prasad, K. 2008. Biosynthesis of silver nanoparticles using Eclipta leaf, Biotechnology Progress, [68] Jha, K.A. and Prasad, K. 2009. Biosynthesis of silver nanoparticles using Cycas leaf broth. Bioprocess Biosystems Eng., [69] Jo, K.Y., Kim, H.B. and Jung, G. 2009. Antifungal Activity of Silver Ions and Nanoparticles on Phytopathogenic Fungi. Plant Disease, 93(10):

1037-1043. [70] Joseph, T. and Morrison, M. Nanotechnology in Agriculture and Food. [Online]. Available:

http://www.nanoforum.org/nf06/modul/showmore/folder /99999/scid/377/.html?action=long view publication& [6 June 2008]. [71] Jung, W., Koo, H., Kim, K., Shin, S., Kim, S. and Park, Y. 2008. Antibacterial activity and mechanism of action of the silver ion in

Staphylococcus aureus and Escherichia coli. Appl Environ Microbiol, 74: 2171–2178. [72] Kalishwaralal, K., Banumathi, E., Pandian, S.B.R.K., Deepak, V., Muniyandi, J. and Eom, S.H. 2009. Silver nanoparticles inhibit VEGF induced

cell proliferation and migration in bovine retinal endothelial cells. Colloids Surf B, 73: 51–7. [73] Kalishwaralal, K., Deepak, V., Ramkumarpndian, S., Nellaiah, H., and Sangiliyandi, G. 2008. Extracellular biosynthesis of silver nanoparticles

by the culture supernatant of Bacillus licheniformis. Materials Letters, 62: 4411-4413. [74] Kathiresan, K., Manivannan, S., Nabeel, A.M. and Dhivya, B. 2009. Studies on silver nanoparticles synthesized by a marine fungus Penicillum

fellutanum isolated from coastal mangrove sediment. Colloids Surfaces B: Biointerfaces, 71: 133-137. [75] Khandelwal, N., Singh, A., Jain, D., Upadhyay, M.K. and Verma, H.N. 2010. Green synthesis of silver nanoparticles using Argimone mexicana

leaf xtract and evaluation of their antimicrobial activities. Digest Journal of Nanomaterials and Biostructures, 5(2): 483 – 489. [76] Kim, J. 2007. Antibacterial activity of Ag? ion-containing silver nanoparticles prepared using the alcohol reduction method. J Ind Eng Chem

13:718–722. [77] Kim, H.S., Kang, H.S., Chu, G.J. and Hong, S.B. 2008. Antifungal effectiveness of nanosilver colloid against rose powder mildew in

greenhouses. Solid state Phenomena, 135: 15-18. [78] Klaus, T., Joerger, R., Olsson, E. and Granqvist, C. 1999. Silver-based crystalline nanoparticles, microbially fabricated. Proc. Natl. Acad. Sci.,

96(24): 13611-13614. [79] Kong, H., Jang, J. 2008. Antibacterial properties of novel poly(methyl methacrylate) nanofiber containing silver nanparticles, Langmuir, 24:

2051-2056. [80] Kowshik, M., Vogel, W., Urban, J., Kulkarni, S.K. and Paknikar, K.M. 2002. Microbial synthesis of semiconductor PbS nanocrystallites.

Biotechnol. Bioeng. Adv. Mater., 14: 815-818. [81] Kowshik, M., Ashtaputre, S., Kharrazi, S., Vogel, W., Urban, J., Kulkarni, S. K. and Paknikar, K.M. 2003. Extracellular synthesis of silver

nanoparticles by a silver- tolerant yeast strain MKY3. Nanotechnology, 14: 95-100. [82] L’opeza, M.L., Parsonsb, J.G., Peralta Videab, J.R. and Gardea-Torresdey, T.L. 2005. An XAS study of the binding and reduction of Au(III) by

hop biomass. Microchem J 81:50–56. [83] Law, N., Ansari, S., Livens, F.R., Renshaw, J.C., Lloyd, J.R. 2008. The formation of nano-scale elemental silver particles via enzymatic

reduction by Geobacter sulfurreducens. Appl Environ Microbiol, 74: 7090–7093. [84] Leela, A. and Vivekanandan, M. 2008. Tapping the unexploited plant resources for the synthesis of silver nanoparticles. African Journal of

Biotechnology, 7(17): 3162-3165. [85] Lengke, F.M., Fleet, E.M., Southam, G. 2007. Biosynthesis of silver nanoparticles by filamentous cyanobacteria a from a silver (I) nitrate

complex, Langmuir, 23: 2694- 2699. [86] Li, P., Li, J., Wu, C., Wu, Q. and Li, Li. 2005. Synergistic antibacterial effects of beta lactam antibiotic combined with silver nanoparticles,

Nanotechnology 16: 1912–1917. [87] Li, S., Shen, Y., Xie, A., Yu, X., Qiu, L. and Zhang L. 2007. Green synthesis of silver nanoparticles using Capsicum annuum L. extract. Green

Chem., 9: 852–885. [88] Liau, S., Read, D., Pugh, W., Furr, J. and Russell, A. 1997. Interaction of silver nitrate with readily identifiable groups: relationship to the

antibacterial action of silver ions. Lett Appl Microbio,l 25: 279–283. [89] Linga Rao, M. and N. Savithramma. 2011. Biological Synthesis of Silver Nanoparticles using Svensonia Hyderabadensis Leaf Extract and

Evaluation of their Antimicrobial Efficacy. J. Pharm. Sci. & Res. .3(3): 1117-1121. [90] Liu, J. and Lu, Y. 2004. Colorimetric biosensors based on DNAzyme-assembled gold nanoparticles. J Fluoresc 14:343–354.

242 ©FORMATEX 2011


[91] Liu, W.T. 2006. Nanoparticles and their biological and environmental applications J Biosci Bioeng, 102 (1): 1–7. [92] Lok, C., Ho, C., Chen, R., He, Q., Yu, W., Sun, H., Tam, P., Chiu, J. and Che, C. 2006. Proteomic analysis of the mode of antibacterial action of

silver nanoparticles. J Proteome Res, 5: 916–924. [93] Maensiria, S., Laokula, P., Klinkaewnaronga, J., Phokhaa, S., Promarakc, V. and Seraphin, S. 2008. Indium oxide (In2O3) nanoparticles using

Aloe vera plant extract: Synthesis and optical properties. Journal of Optoelectronics and Advanced Materials, 10(3): 161 – 165. [94] Maggy, F.L., Michael, E.F. and Gordon, S. 2007. Biosynthesis of silver nanoparticles by filamentous cyanobacteria from a silver (I) nitrate

complex. Langmuir, 23: 2694-2699. [95] Margarita Stoytcheva. 2011. Pesticides Formulations, Effects, Fate. InTech Janeza Trdine 9, 51000 Rijeka, Croatia. [96] Margraff, H.W. and Covey, T.H. 1977. A trial of silver–zinc-allantoine in the treatment of leg ulcers. Arch Surg, 112: 699–704. [97] Marcato1, P.D., G.I.H. De Souza, O.L. Alves, E. Esposito, N. Durán. 2005. Antibacterial activity of silver nanoparticles synthesized by

Fusarium oxysporum strain. 4th Mercosur Congress on Process Systems Engineering. PP. 5. [98] McNeil, SE. 2005. Nanotechnology for the Biologist. J Leukoc Biol, 78: 585–94. [99] Mendis, E., Rajapakse, N., Byun, H. and Kim, S. 2005. Investigation of jumbo squid (Dosidicus gigas) skin gelatin peptides for their in vitro

antioxidant effects. Life Sci, 77: 2166–2178. [100] Min, J.S., Kim, K.S., Kim, S.W., Jung, J.H., Lamsal, K., Kim, S.B. Jung, M. and Lee, Y.S. 2009. Effects of Colloidal Silver Nanoparticles on

Sclerotium-Forming Phytopathogenic Fungi. Plant Pathol. J., 25(4): 376-380. [101] Mohanpuria, P., Rana, N.K. and Yadav, S.K. 2008. Biosynthesis of nanoparticles: technological concepts and future applications. J Nanopart

Res, 7: 9275–9280. [102] Mokhtari, M., Deneshpojouh, S., Seyedbagheri, S., Atashdehghan, R., Abdi, K., Sarkar, S., Minaian, S., Shahverdi, R.H. and Shahverdi, R.A.

2009. Biological synthesis of very small silver nanoparticles by culture suspernatant of Klebsiella pneumonia. The effects of visible-light irradiation and the liquid mixing process, Materials Research Bull, 44: 1415-1421.

[103] Morones, J., Elechiguerra, J., Camacho, A., Holt, K., Kouri, J., Ramirez, J. and Yacaman, M. 2005. The bactericidal effect of silver nanoparticles. Nanotechnology, 16: 2346–2353.

[104] Mukherjee, P., Ahmad, A., Mandal, D., Senapati, S., Sainkar, R.S., Khan, I.M., Parishcha, R., Ajaykumar, V.P., Alam, M., Kumar, R. and Sastry, M. 2001. Fungus-mediated synthesis of silver nanoparticles and their immobilization in the mycelia matrix. A novel biological approach to nanoparticle synthesis. Nano Letters, 1(10): 515-519.

[105] Mukherjee, P., Bhattacharya, R., Bone, N., Lee, Y.K., Patra, C.R. and Wang S. 2007. Potential therapeutic application of gold nanoparticles in B-chronic lymphocytic leukemia (BCLL): enhancing apoptosis. J Nanobiotechno,l 5: 4.

[106] Muñoz, Z., Moret, A. and Garces, S. 2009 Assessment of chitosan for inhibition of Colletotrichum sp. on tomatoes and grapes. Crop Prot, 28:36–40.

[107] Musarrat, J., Dwivedi, S., Singh, B.R., Al-Khedhairy, A.A., Azam, A. and Naqvi, A. 2010. Production of antimicrobial silver nanoparticles in water extracts of the fungus Amylomyces rouxii strain KSU-09. Bioresource Technology, 101: 8772–8776.

[108] Nair, B. and Pradeep, T. 2002. Coalescence of nanoclusters and formation of submicron crystallites assisted by Lactobacillus strains. Crystal Growth Des., 2(4): 293-298.

[109] Nel, A., Xia, T., Madler, L. and Li, N. 2006. Toxic potential of materials at the nanolevel. Science, 311: 622–627. [110] Paciotti, G.F., Myer, L., Weinreich, D., Goia, D., Pavel, N. and McLaughlin, R.E. 2004. Colloidal gold: a novel nanoparticle vector for tumor

directed drug delivery. Drug Deliv 11:169–183. [111] Park, H., Kim, J., Kim, J., Lee, J., Hahn, J., Gu, M. and Yoon, J. 2009. Silver-ion-mediated reactive oxygen species generation affecting

bactericidal activity. Water Res, 43: 1027–1032. [112] Petering, H. 1976. Pharmacology and toxicology of heavymetals- silver. Pharmacol Ther A, 1: 127–130. [113] Philip, D.2010. Green synthesis of gold and silver nanoparticles using Hibiscus rosa sinensis. Physica E: Low-dimensional Systems and

Nanostructures 42 (5): 1417-1424. [114] Philip, D., Unnib, S., Aswathy Aromala., V.K. and Vidhua. 2011a. Murraya Koenigii leaf-assisted rapid green synthesis of silver and gold

nanoparticles Spectrochimica Acta Part A, 78: 899–904. [115] Philip, D. 2011b. Mangifera Indica leaf-assisted biosynthesis of well-dispersed silver nanoparticles. Spectrochimica Acta Part A, 78: 327–331. [116] Prabhu, N., Divya., Raj, T., Gowri, Y.K., Siddiqua, A.S. and Innocent, J.P. 2010. Synthesis of silver phyto nanoparticles and their antibacterial

efficacy. Digest Journal of Nanomaterials and Biostructures, 5(1): 185 – 189. [117] Prasad, K., Jha, A.K. and Kulkarni, A.R. 2007. Lactobacillus assisted synthesis of titanium nanoparticles. Nanoscale Res. Lett., 2: 248-250. [118] Prathnaa, T.C., Chandrasekarana, N., Ashok, Raichurb, M. and Amitava Mukherjee. 2011. Biomimetic synthesis of silver nanoparticles by

Citrus limon (lemon) aqueous extract and theoretical prediction of particle size. Colloids and Surfaces B: Biointerfaces, 82: 152–159. [119] Raffi, M., Hussain, F., Bhatti, T., Akhter, J., Hameed, A. and Hasan, M. 2008. Antibacterial characterization of silver nanoparticles against E.

coli ATCC-15224. J Mater Sci Technol, 24: 192–196. [120] Rai, A., Singh, A., Ahmad, A. and Sastry, M. 2006. Role of halide ions and temperature on the morphology of biologically synthesized gold

nanotriangles. Langmuir, 22: 736–741. [121] Rai, M., Yadav, A. and Gade, A. 2008. Current trends in phytosynthesis of metal nanoparticles. Crit Rev Biotechnol, 28(4): 277–284. [122] Rai, M., Yadav, A. And Gade, A. 2009. Silver nanoparticles as a new generation of antimicrobials, Biotechnology Advances, 27: 76-83. [123] Rajesh, W.R., Jaya R.J., Niranjan, S.K., Vijay, D.M. and Sahebrao, K.B. 2009. Phytosynthesis of Silver Nanoparticle Using Gliricidia sepium

(Jacq.). Current Nanoscience, , 5: 117-122. [124] Ren, X., Meng, X. and Tang, F. 2005. Preparation of Ag–Au nanoparticle and its application to glucose biosensor. Sensor Actuat B, 110: 358–

363. [125] Revina, A.A. and Egorova, E.M. Radiation-chemical technology for the synthesis of stable metallic and bimetallic clusters, in International

Conference on Advances in Technology in the 21st Century (ICAT ‘98), Moscow, 5–9 October, pp. 411–413, 1998. [126] Rodriguez, E., Parsons, J.G., Peralta-Videa, J.R., Cruz-Jimenez, G., Romero- Gonzalez, J. and Sanchez-Salcido, B.E. 2007. Potential of

Chilopsis linearis for gold phytomining: using XAS to determine gold reduction and nanoparticle formation within plant tissues. Int J Phytoremed, 9: 133–147.

[127] Rosi, N.L. and Mirkin, C.A. 2005. Nanostructures in Biodiagnostics. Chem Rev, 105: 1547–62. [128] Roy, N. and Barik, A. 2010. Green Synthesis of Silver Nanoparticles from the Unexploited Weed Resources. International Journal of

Nanotechnology and Applications, 4(2): 95-101. [129] Sadowski, Z., Maliszewska, I., Polowczyk, I., Kozlecki, T. and Grochowalska, B. 2008a. Biosynthesis of colloidal-silver particles using

microorganisms, Polish J. Chem, 82: 377-382. [130] Sadowski, Z., Maliszewska, H.I., Grochowalska, B., Polowczyk, I. and Kozlecki, T. 2008b. Synthesis of silver nanoparticles using

microorganisms, Materials Science-Poland, 26(2): 419-424. [131] Saifuddin, N., Wang, W.C., Nur Yasumira, A.A. 2009. Rapid biosynthesis of silver nanoparticles using culture supernatant of bacteria with

microwave irradiation, E JournalChem., 6(2): 61-70.

243©FORMATEX 2011


[132] Saravanan, M. 2010. Biosynthesis and In vitro Studies of Silver Bionanoparticles Synthesized from Aspergillus species and its Antimicrobial Activity against Multi Drug Resistant Clinical Isolates. World Academy of Science, Engineering and Technology, 68: 728 – 731.

[133] Sastry, M., Ahmad, A., Khan, M.I. and Kumar, R. 2003. Biosynthesis of metal nanoparticles using fungi and actinomycete. Curr. Sci., 85: 162-170.

[134] Sathishkumar, M., Sneha, K., Won, W.S., Cho, C-W., Kim, S. and Yun, Y-S. 2009. Cynamon zeylanicum bark extract and powder mediated green synthesis of nanocrystalline silver particles and its bactericidal activity, Colloids Surfaces, B:Biointerfaces, 73: 332- 338.

[135] Sathyavathi, R., Balamurali Krishna, M., Venugopal Rao, S., Saritha, R. and Narayana Rao, D. 2010. Biosynthesis of Silver Nanoparticles Using Coriandrum Sativum Leaf Extract and Their Application in Nonlinear Optics. Advanced Science Letters 3: 1–6.

[136] Schreurs, W. and Rosenberg, H. 1982. Effect of silver ions on transport and retention of phosphate by Escherichia coli. J Bacteriol, 152: 7–13. [137] Shahverdi, A.R., Fakhimi, A., Hamid, R., Shahverdi. and Minaian, S.M.S. 2007. Synthesis and effect of silver nanoparticles on the antibacterial

activity of different antibiotics against Staphylococcus aureus and Escherichia coli. Nanomedicine: Nanotechnology, Biology, and Medicine, 3:168– 171.

[138] Shahverdi, R.A., Minaeian, S., Shahverdi, R.H., Jamalifar, H. and Nohi, A-A. 2007. Rapid synthesis of silver nanoparticles using culture supernatants of Enterobacteria: A novel biological approach. Process Biochemistry, 42: 919-923.

[139] Shankar, S., Ahmad, A. and Sastry, M. 2003. Geranium leaf assisted biosynthesis of silver nanoparticles, Biotechno. Prog., 19: 1627-1631. [140] Shankar, S., Rai, A., Ahmad, A. and Sastry, M. 2004. Rapid synthesis of Au, Ag and bimetallic Au core-Ag shell nanoparticles using Neem

(Azadirachta indica) leaf broth. J. Colloid Inter. Sci., 275: 496-502. [141] Shankar, S.S., Rai, A., Ahmad, A. and Sastry, M. 2005. Controlling the optical properties of lemongrass extract synthesized gold nanotriangles

and potential application in infrared-absorbing optical coatings. Chem Mater., 17: 566–572. [142] Sharma, N.C., Sahi, S.V., Nath, S., Parsons, J.G., Gardea-Torresdey, J.L. and Pal, T. 2007. Synthesis of plant-mediated gold nanoparticles and

catalytic role of biomatrix-embedded nanomaterials. Environ Sci Technol., 41: 5137–5142. [143] Sharma, V.K., Yngard, R.A. and Lin, Y. 2009. Silver nanoparticles: green synthesis and their antimicrobial activities. Adv Colloid Interface Sci,

145: 83–96. [144] Sheikpranbabu, S., Kalishwaralal, K., Venkataraman, D., Eom, S.H., Park, J. and Gurunathan, S. 2009. Silver nanoparticles inhibit VEGF-and

IL-1b-induced vascular permeability via Src dependent pathway in porcine retinal endothelial cells. J. Nanobiotechnol 7: 8. [145] Shirley, A., Dayananda, B., Sreedhar, B., Syed, G. and Dastager, C.C. 2010. Antimicrobial activity of silver nanoparticles synthesized from

novel Streptomyces species. Digest Journal of Nanomaterials and Biostructures. 5(2): 447 – 451. [146] Shiying, H., Zhirui, G., Yu, Z., Song, Z., Jing, W. and Ning, G. 2007. Biosynthesis of gold nanoparticles using the bacteria Rhodopseudomonas

capsulata. Mater. Lett., 61: 3984-3987. [147] Shrestha, S., Yeung, C.M.Y., Nunnerley, C. and Tsang, S.C. 2007. Comparison of morphology and electrical conductivity of various thin films

containing nano-crystalline praseodymium oxide particles. Sens. Actuators A: Phys, 136: 191. [148] Silver, S. 2003. Bacterial silver resistance: molecular biology and uses and misuses of silver compounds. FEMS Microbiol Rev., 27: 341–353. [149] Singh, A., Chaudhary, M. and Sastry, M. 2006. Construction of conductive multilayer films of biogenic triangular gold nanoparticles and their

application in chemical vapour sensing. Nanotechnology, 17: 2399–2405. [150] Smetana, A., Klabunde, K. and Sorensen, C. 2005. Synthesis of spherical silver nanoparticles by digestive ripening, stabilization with various

agents, and their 3-D and 2-D superlattice formation. J Colloid Interface Sci, 284:521–526. [151] Sondi, I. and Salopek-Sondi, B. 2004. Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria.

J Colloid Interface Sci, 275: 177– 182. [152] Song, J.Y. and Kim, B.S. 2009. Rapid biological synthesis of silver nanoparticles using plant leaf extracts. Bioprocess Biosyst Eng., 32: 79–84. [153] Song, J.Y., Kwon E.Y. and Kim, B.S. 2010. Biological synthesis of platinum nanoparticles using Diopyros kakileaf extract. Bioprocess and

Biosystems Engineering, 33(1): 159-164. [154] Stohs, S.J. and Bagchi, D. 1995. Oxidative mechanisms in the toxicity of metal-ions. Free Radic Biol Med, 18: 321–336. [155] Tang, D., Yuan, R. and Chai, Y. 2006. Ligand-functionalized core/shell Ag–Au nanoparticles label-free amperometric immun-biosensor.

Biotechnol Bioeng., 94: 996–1004. [156] Taniguchi, N. 1974. On the basic concept of nano-technology Proceedings of the International Conference on Production Engineering Tokyo

Part II Japan Society of Precision Engineering. [157] Thakkar, K.N., Mhatre, S.S. and Parikh, R.Y. 2010. Biological synthesis of metallic nanoparticles. Nanomedicine, 6(2): 257–262. [158] Thanh, N.T.K. and Rosenzweig, Z. 2002. Development of an aggregation-based immunoassay for anti-protein A using gold nanoparticles. Anal

Chem 74: 1624–1628. [159] Thirumurugan, G., Shaheedha, S.M. and Dhanaraju, M.D. 2009. In vitro evaluation of antibacterial activity of silver nanoparticles synthesised

by using Phytophthora infestans. Int J ChemTech Res, 1: 714–716. [160] Tripathy, A., Raichur, M.A., Chandrasekaran, N., Prathna, T.C. and Mukherjee, A.2010. Process variables in biomimetic synthesis of silver

nanoparticles by aqueous extract of Azadirachta indica (Neem) leaves Journal of nano research, 12(1): 237-246. [161] Yanez-Sedeno, P. and Pingarron, J.M. 2005. Gold nanoparticle-based electrochemical biosensors. Anal Bioanal Chem 382:884–886. [162] Yang, W., Shen, C., Ji, Q., An, H., Wang, J., Liu, Q. and Zhang, Z. 2009. Food storage material silver nanoparticles interfere with DNA

replication fidelity and bind with DNA. Nanotechnology, 20. [163] Zhang, Y., Yang, D., Kong, Y., Wang, X., Pandoli, O. and Gao, G. 2010. Synergetic Antibacterial Effects of Silver Nanoparticles@Aloe Vera

Prepared via a Green Method. Nano Biomed. Eng., 2(4): 252-257. [164] Zhu, S., Du, CL. and Fu, Y. 2009. Fabrication and characterization of rhombic silver nanoparticles for biosensing, Optical Materials, 31: 769-

774. [165] Zong, R.L., Zhou, J., Li, Q., Du, B., Li, B. and Fu, M. 2004. Synthesis and optical properties of silver nanowire arrays embedded in anodic

alumina membrane J Phys Chem B, 108: 16713–16716.

244 ©FORMATEX 2011


Bionanoparticles Synthesis and Antimicrobial Applications

Documents

Transcript of Bionanoparticles Synthesis and Antimicrobial Applications