Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 ISSN: 2231-2560 CODEN (USA): AJBPAD Review Article Asian Journal of Biochemical and Pharmaceutical Research Nanosilver Products - A Review Vikas Gupta1 and Ajay Kumar*2 1. GTBIT, Rajouri Garden, New Delhi -110065 2. Galgotias University, Plot No-2, Sector17A, Yamuna Expressaway, Distt Gautam Budh Nagar, UP Received: 17 November 2014; Revised: 04 December 2014; Accepted: 19 December 2014 Abstract: Review article describes the importance of nano dimensions in product development. Nanosilver EPA approved products such as silver biocidal additives, silver-impregnated water filters and silver algaecides and disinfectants historic development is described. Recent applications of silver nano particles in medical devices, silver dressings, silver coated textile fabrics, silver-nano particle-embedded antimicrobial paints, antimicrobial surface functionalization of plastic catheters, antimicrobial gel formulation for topical use, antimicrobial packing paper for food preservation, silver-impregnated fabrics for clinical clothing, nano silver children products and products for pets are described. Nanosilver products safety data available in EPA’s formal incident reporting database (EPA OPP IDS) indicates that nanosilver products are safe. Nanosilver has been safely used in direct aquatic applications and dermal wound care since decades. Exposure of nanosilver products is far less than to conventional silver products and synthetic chemical antimicrobials Keywords: Nano silver particles, microorganism, biocidal, algaecides, disinfectants, EPA INTRODUCTION: Silver is extracted from argentitle (Ag2S) and horn silve AgCl). Pure silver and its alloys are used in coinage, silver ware , jewellery widely. Silver is also used in electroplating, dental amalgam, batteries, photography etc. Silver has been used in the treatment of human diseases such as neonatal eye disease , cholera and wound infection. Silver wire suture was used in hernia operation and silver foil for preventing post operation infection. Silver has an ancient history of purification of potable water. Earlier examples are ancient dynasties of the Egypt and Middle East. In India ,Maharaja of Jaipur used fashionable silver urns to transport sacred Ganga river water [1,2]. Killing of antibiotic resistant microbe/ microorganism by the low concentration of silver/ metal at low concentration is known as “oligodynamic effect” [2]. The oligodynamic action of silver ions is observed at .3 to 2 ppm [3-7].This proves antibacterial effects of silver ion is higher than most of the bactericidal metals followed by mercury, lead and copper [2]. The silver nitrate drops are still used to prevent contracting gonorrhea from mother to new born [1,8]. Silver ions has been used in healthcare facilities [9,10] cosmetics , air/water filters , food packaging containers and textiles [ 11]. Silver nanoparticles are produced by reduction of silver ions have spherical, prism , cubic or rod morphologies and size of at least one dimension in 1-100 nm. Due to smaller size silver nanoparticles have more surface area. Because of this they are better catalyst and more bioactive than the bulk silver. The color of silver nanoparticles is size dependent. Silver nanoparticles show longer 91 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD lasting biocidal effect than silver ion. However, AgNPs tend to form aggregates in the aqueous phase, which gradually diminishes their efficacy in long term use [11]. The silver nanoparticle can easily be immobilized on the solid matrix such as glass, plastics, paper and ceramics. The immobilization of silver nanoparticles on solid matrix would became an effective disinfection system and would reduce the associated environmental threats. Not only this the immobilized silver nanoparticles can be used multiple times. The biocidal properties of silver nanoparticles have made silver nanoparticle a important item to make commercial products. The Woodrow Wilson Database lists over 313 commercial products that contain silver nanoparticles. [12].These products include healthcare, cosmetics, food packaging, health supplements, air/water filters, detergents etc[12,13]. Although silver ions/nanoparticles and other compounds have shown great success in many antimicrobial applications but are not without some problems. Some bacteria have evolved resistance to many antibiotics, including silver. Resistance refers to the ability of bacteria to reproduce in high concentrations of a disinfectant or antibiotic [14]. Silver – resistant bacteria were first isolated from environments contaminated with silver , such as polluted soil near silver mine drainage areas, skin burn wound regions, watersheds , near photographic industry effluents etc. [5, 15-17]. Gene encoding silver resistance in bacteria are carried on plasmids, which have been found in Pseudomonas stutzeri that were isolated from silver mine [18] and E coli [19]. Differing mechanisms explain silver resistance in bacteria, which include either cell wall impermeability to metal ions or metal accumulation within the cells [16,20]. Recently, it has been shown that hazard assessment of a silver nanoparticle in soil applied via sewage sludge because toxic effects on soil microorganisms of the terrestrial ecosystem. { 21]. Silver nanoparticles are also biomagnified and effect aquatic life [ 22-24]. The silver can be toxic to humans [25,26]. Therefore nanosilver product safety must be considered before using silver nano particle products. In this report we review antibacterial mechanism of action of silver, history and applications of silver nano products and their safety concerns. Antibacterial mechanism of silver: The lowest concentration of an antimicrobial that inhibits visible growth of a microorganism after overnight incubation in a specified culture medium is called mimimum inhibitory concentration (MIC) [27]. The MIC is used to confirm resistance of microorganism to an antimicrobial. MIC is also used to compare the activity of new antimicrobials[ 27]. Both silver ions and silver nanoparticles are used as bactericidal agent. The toxic effect of both silver ions and silver nanoparticles is in similar concentration range for Escherichia Coli, staphylococcus aureus, human mesenchymal stem cells and blood peripheral mono layers cells [28]. However, silver nanoparticles are more effective in terms of MIC than their ionic homologues [7, 29, 7, 30-37]. The biocidal effect of silver nanoparticles strongly depends on their size . The smaller particle showed greater biocidal effect than bigger one [ 38] due the presence of more number of atoms on the surface [37,39]. Recently size selective comparison of silver nanoparticle biocidal activity against various Gram- positive and Gram –negative strain showed that biocidal effect is enhanced as the size of nanoparticles approached the sub 10 nm range and 5 nm silver nanoparticles demonstrated fastest bactericidal activity as compared to 7 nm and 10 nm silver nanoparticles at their respective MIC dosage[ 40]. A list of microorganisms inactivated by silver ions and /or nanoparticles is listed [41] in table-1. 92 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD The biocidal action of silver ions has been explained by various mechanism. The interaction of thiol group of amino acids such as cysteine and other thiol group containing compounds such as sodium thioglycolate, present in enzyme and protein , neutralize the activity of silver bacteria[ 33, 42]. Silver ions cause the release of K+ from bacteria, thus bacterial plasma or cytoplasmic membrane is an important target site for silver ion. The action of silver nanoparticles make a hole in the membrane, which causes leakage of important enzymes[ 31,35]. In addition to this silver ions cause inhibition of bacterial growth by depositing in vacuoles and cell walls [43]. Silver ions also interact with DNA bases and cause DNA aggregation [36, 42]. Inhibition of activity of enzymes of nitrifying bacteria [44], bacterial respiration and ATP synthesis has also been reported [45].Superoxide radicals produced by silver nanoparticles penetrate into the cell membrane [46]. Nanosilver Products History: The worldwide production of silver reached approximately 28,000 metric tons in 2007 [75], approximately 500 metric tons per year are nanosilver [76]. The majority of silver is used in industry (38.2%), as jewelry and silverware (32.5%), and in the photographic industry (23.8%). Silver biocide use (0.5% or approximately 140 metric tons) is still very small and the remainder of the silver is used for investment and coins (5%) [75]. In 1889, M. C. Lea reported the synthesis of a citrate stabilized silver colloid [77]. The average diameter for the particles obtained by this method was between 7 and 9 nm [78]. The size and the stabilization of nanoparticle prepared by citrate method are identical to recent methods used to prepare nanosilver particles using silver nitrate and citrate, [79, 80]. The stabilization of nanosilver using proteins has been described as early as 1902 [81] and a product “Collargol” containing such a kind of nanosilver has been manufactured commercially since 1897 for medical applications[82]. Collargol contains silver of particle size of 10 nm [83]. As early as 1907 its diameter was determined to be in the nano range [84]. Gelatin stabilized silver nanoparticles with 2-20 nm diameter was patented by Moudry in 1953 [85]. The silver nanoparticle impregnated carbon with a diameter of silver particles below 25 nm has been patented [86]. Long ago inventors of nanosilver formulations understood that the viability of the technology required nanoscale silver. The inventors made a statement from a patent: “for proper efficiency, the silver must be dispersed as particles of colloidal size less than 250 Å [less than 25 nm] in crystallite size” [86]. The above formulations have consistently found into the market since last over a 50-year period and their use has become widespread to treat various diseases such as syphilis and other bacterial infections. [87]There are at least three categories of EPA-registered products that employ elemental silver particles with particle sizes less than 100 nm: (a) silver biocidal additives; (b) silverimpregnated water filters; (c) silver algaecides and disinfectants. Several examples of each category are identified below:Silver Biocidal Additives: EPA has registered numerous biocidal additives based on elemental silver particles. Some examples of currently registered biocidal additive products that contain metallic (elemental) silver with very small particle size (<100 nm), are Additive SSB (EPA reg. 83587-3, company NanoHorizons), Micro Silver BG-R (EPA reg. 84146-1, company Bio-Gate), and HyGate 4000 (EPA reg. 70404-10, company BASF, formerly Ciba Corp.). These silver biocides are typically used in plastic and textile applications where the silver is effectively contained within polymer substrates. 93 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Silver Algaecides and Disinfectants: Colloidal nanosilver algaecides are elemental silver in very small particle size (e.g., <100 nm) maintained in a stabilized solution. Some examples of currently registered biocidal products are Silver Algaedyn (EPA reg. 68161-1, Pool Products Packaging Corp), Nu-Clo Silverside (EPA reg. 7124-101, Alden Leeds Inc.) and ASAP-AGX (EPA reg. 73499-1, American Biotech Laboratories). It should be noted that algaecide applications have been used safely in high-exposure, direct water contact, and down-the-drain applications such as swimming pool disinfection for decades without any known damaging impact on humans or the environment. Silver - Impregnated Water Filters: EPA has registered multiple silver-impregnated water filters since the 1970s based on activated carbon or ceramics that are impregnated with very small particle size (<100 nm) metallic (elemental) silver. The impregnation of carbon and ceramic materials with metals is widely recognized as a standard technique for the synthesis of nanoscale metal particles. The wet impregnation methods employed in production of nanostructured industrial catalysts for decades have been reviewed [88-90]. Silver-impregnated water filters currently registered under FIFRA employ similar methods with the clear intention to produce nanoscale silver. For example, the elemental silver preferably includes at least 2% of silver crystals having crystal sizes between approximately 3nm and 10nm [90, 91]. Silver-impregnated water filters have been safely used for domestic water applications such as drinking water and swimming pool filters for decades. No reports about any health or environmental effects have been reported, although the absence of such reports does not mean that no effects occurred. Recent Applications of Nanosilver particles Silver coated medical devices: Silver nanoparticles can be used for the impregnation of medical devices such as surgical masks [95]. The advantage of impregnation of medical devices with silver nanoparticles is that it protects both outer and inner surfaces of devices and there is continuous release of silver ions providing antimicrobial activity [96, 97]. Variety of methods has been used to test the efficacy of silver nanoparticles impregnated on silicon elastomer [86] and it is found that the antibacterial efficiency of silver nanoparticles reduces after washing. The reason for this might be the inactivation of metallic silver when it comes in contact with blood plasma and the lack of durability of the coatings [92-94]. Silver dressings: Dressings play a major part in the management of wounds [98]. In recent times, the development of resistant strains of pathogens has become a major problem and the newly designed wound dressings have provided a major breakthrough for the treatment of infection and wounds. The antibacterial properties and the toxicity of silver to micro-organisms are well known, thus, now a day, silver is also used in wound dressing [99]. The silver dressings make use of delivery systems that release silver in different concentrations. But different factors like the distribution of silver in the dressing, its chemical and physical form, affinity of dressing to moisture influence the killing of microorganisms [100]. Silver coated textile fabrics: Researchers are developing textile fabrics containing antibacterial agents. As, silver is non-toxic and possess antimicrobial properties, it has encouraged workers to use 94 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD silver nanoparticles in different textile fabrics. Silver nano composite fibers were prepared containing silver nanoparticles inside the fabric. But scanning electron microscopic studies have shown that the silver nanoparticles incorporated in the sheath part of fabrics possessed significant antibacterial property as compared to the fabrics in which silver nanoparticles are incorporated in the core part [101]. It is also reported that silver nanoparticles coated textile fabrics possess antibacterial activity against S. aureus [99]. Silver-nanoparticle-embedded antimicrobial paints: The bactericidal coatings on surface are important to protect human health and the environment. The Ag-NPs-embedded coatings are of particular interest owing to their potential bactericidal activity. John et al [102] has developed an environmentally friendly method to synthesize metal NPs-embedded paint, in a single step, from common household paint. The naturally occurring oxidative drying process in oils, involving freeradical exchange, was used as the fundamental mechanism for reducing metal salts and dispersing metal NPs in the oil media, without the use of any external reducing or stabilizing agents. These welldispersed metal NPs-in-oil dispersions can be used directly on different surfaces such as wood, glass, steel and different polymers. The results showed that the surfaces coated with silver-nanoparticle paint have excellent antimicrobial properties by killing both gram-positive human pathogens (S. aureus) and gram-negative bacteria (E. coli). The market potential for silver containing paints and lacquers is currently very small and is expected to be relatively insignificant when compared to other consumer products. There are few products on the market, but examples include: silver containing biocide (TINOSAN® SDC, IRGAGUARD® by Ciba Specialty Chemicals) which can be used as a plastic additive and can be used to produce coating effects. Alfred Clouth Lackfabrik produces nanosilver containing wood lacquers (CLOUCRYL Nano-Finish ANTIBAK and WL-Nano CB ANTIBAK) sell between 3 - 5 metric tons of these per year. The lacquers contain silver particles bound in a polymer film at a concentration of 100 - 300 ppm silver/kg lacquer [75]. Antimicrobial surface functionalization of plastic catheters: Silver nanoparticles have been used to coat catheters [103]. Silver-coated catheters showed significant in vitro antimicrobial activity and prevented biofilm formation against pathogens (E. coli, Enterococcus, S. aureus, coagulase-negative staphylococci, P. aeruginosa and C. albicans); most of them involved in catheter-related infections. These catheters are non-toxic. They sustained release silver at the implantation site. Because of their demonstrated antimicrobial properties, they may be useful in reducing the risk of infectious complications in patients with indwelling catheters. Antimicrobial gel formulation for topical use: The Ag-NPs were also used in therapeutics, for treating burn wounds. A gel formulation containing Ag-NPs (S-gel) [104] was found to be comparable to that of a commercial formulation of silver sulfadiazine. The cell viability, biochemical effects and apoptotic/necrotic potential were assessed by localization of Ag-NPs in Hep G2 cell line. It was found that Ag-NPs get localized in the mitochondria and have an IC50 value of 251 μg ml−1which indicate that Ag-NPs induced apoptosis at concentrations up to 250 μg ml−1. This favors scarless wound healing. Acute dermal toxicity studies on Ag-NPs gel formulation (S-gel) Sprague-Dawley in rats showed complete safety for topical application. Hence, Ag-NPs could provide a safer alternative to conventional antimicrobial agents in the form of a topical antimicrobial formulation. 95 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Antimicrobial packing paper for food preservation: The preventing microbial growth for longer periods in food preservation can be carried out by packing the processed food in antimicrobial packing. The silver nanoparticles containing papers using ultrasonic radiation have been developed [105]. By varying the precursor concentrations and reaction times, the thickness of the Ag-NPs coating and the particle size was controlled. The Ag-NPs- coated papers thus produced have been shown to possess microbiocidal properties against the Gram-negative E. coli as well as against the Grampositive S. aureus bacteria. The results showed that such Ag-NPs-coated paper has potential application in the food industry as a packing material with a long shelf life and antifouling properties. Silver-impregnated fabrics for clinical clothing: The contamination of clinical clothing with a mixture of bacteria from the wearer and the environment is a common occurrence. The bacteria such as enterococcus and Staphylococcus spp. can survive for more than 90 days on clothing worn by health care workers. The surgical scrub suits (scrubs) may be contaminated by bacteria even when freshly laundered. Also these bacteria can be transferred from nurses' uniforms to patient bedding, and can infect surgical wounds. The effect of silver impregnation of surgical scrub suits on surface bacterial contamination during use in a veterinary hospital was investigated by Freeman et al. [106]. It was found that silver-impregnated scrubs had significantly lowered bacterial colony counts (BCC) compared with suit not treated with silver nanoparticles. This showed that silver impregnation appeared to be effective in reducing bacterial contamination of scrubs during use in a veterinary hospital. Numerous silver nanotechnologies have been launched offering antimicrobial coatings including Bactiguard (Bactiguard AB, Sweden), HyProtect (Bio-Gate AG, Germany), Nucryst’s nanocrystalline platform technology (Nucryst Pharmaceuticals Corp., USA), Spi-ArgentTM (Spire Corp. USA), Surfacine (Surfacine Development Company LLC, USA), and Sylva Gard (AcryMed Inc., USA) . These are used as medical antimicrobials in textiles and surface coating products including wall coating paints, self-sterilizing hospital gowns and bedding. Bioni Hygienic, created by the German based Bioni CS® GmbH Company (see bioni.de) is an example of a nanotech-based antimicrobial nanosilver coating frequently used in hospitals. The company claims its product will create “an antimicrobial surface which prevents the growth of mould and mildew and effectively destroys even the most resistant of hospital bacteria by the use of an entirely new combination of active agents based upon nano technology”[107]. They claim that the 13nm sized nanosilver particles are safely embedded in a matrix that permanently binds the particles to the paint [108]. Nanosilver children products: Nanosilver products targeted towards children and infants include: strollers, toys (stuffed animals), wet wipes, mats and bedding, baby bottles, nipples and pacifiers. For instance, Baby Dream® is a large supplier of baby nanosilver products offering a wide variety of products, including a baby bottle [109]. Also available are stuffed animals with nanosilver treated “Memory Foam” such as Benny the Bear Plush Toy and Donny the Dog sold by Pure Plushy™ Inc. Products for pets: The nanosilver industry has not overlooked pets in its attempt to market products. Nanosilver feeding bowls, deodorants, pet water purifiers, dog beds and pet clothing are now on the market. Saywood Inc. offers a water purifier for pets, which “serves your pet with clean & healthy water preventing bacteria through sterilization & antibiotic effect by the Nano silver photo catalytic coating ball & photo catalytic coating”[110]. 96 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Other Applications: Silver has been known to possess strong antimicrobial properties both in its metallic and nanoparticle forms hence, it has found variety of application in different fields such as:The Fe3O4 attached Ag nanoparticles can be used for the treatment of water and easily removed using magnetic field to avoid contamination of the environment [111]. Silver sulfadazine depicts better healing of burn wounds due to its slow and steady reaction with serum and other body fluids [112]. The nanocrystalline silver dressings, creams, gel effectively reduce bacterial infections in chronic wounds [112, 113]. The silver nanoparticle containing poly vinyl nano-fibres also show efficient antibacterial property as wound dressing (114). The silver nanoparticles are reported to show better wound healing capacity, better cosmetic appearance and scarless healing when tested using an animal model (115). Silver impregnated medical devices like surgical masks and implantable devices show significant antimicrobial efficacy [94]. Environmental-friendly antimicrobial nanopaint can be developed [104]. Inorganic composites are used as preservatives in various products [116]. Silica gel micro spheres mixed with silver thio-sulfate are used for long lasting antibacterial activity {116]. Silver nanoparticles can be used for treatment of burns and various infections [117]. Silver zeolite is used in food preservation, disinfection and decontamination of products [118,119]. Silver nanoparticles can be used for water filtration [120]. Nanosilver Products Safety Nanoscale silver products have been safely regulated since the 1950s: The nanosilver particle products have been regulated by EPA over last 50 years. There is no incident of significance on EPA’s formal incident reporting database (EPA OPP IDS) indicating that silvernano products are safe. Every EPA silver registration between 1970 and the 1990 was in fact a colloidal nanosilver or nanosilvercomposite product. An overall analysis reveals that today over 50% of all EPA registered silver products are based on nanoscale silver [121]. Nanosilver has been safely used in direct aquatic applications for decades: Since 1970 the silver products have been safely used for swimming pools and municipal and domestic drinking water purification. Both swimming pools and domestic water waste ultimately pass to soil, sewage treatment facilities and natural aquatic systems. The reason for low impact is a demonstrated by tendency of silver particles to be strongly passivated by ubiquitous natural environmental complexing agents such as sulphur, chlorides, phosphate and dust [122-126]. The ecological fate and toxicity of environmentally passivated silver, typically forming silver sulphide, is a thoroughly investigated topic, particularly from the long history and high volume of photographic use of silver [127, 128]. Nanosilver is safely used in dermal wound care since decades: There are no ill effects when it is used directly on wounds and broken skin. FDA approved nanosilver dermal wound care ointments and bandages are used routinely in hospitals to promote skin repair by reducing inflammation and such products often save lives by preventing infections [129]. 97 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Exposure is far less than to conventional silver products and synthetic chemical antimicrobials: An exposure analysis in comparison to conventional silver products and synthetic chemical antimicrobials shows significantly lower quantities of active substance are required for nanosilver to achieve an equivalent effect. Such analysis shows a compelling potential for fewer chemicals to be used to treat consumer products and less pollution of the environment. Table 1 Microorganism inactivated by silver ions and /or nanoparticles Type of Type of Microbe Silver Microbe Strain + Ag ions Fungi Protozoa Viruses Enterococcus faecali[46] Vanomycin–RE faecium[34, 53] Escherichia Coli [3, 7,42,53] ESBL-RK pneumoniae[34, 53] Nitrifying bacteria[4] Providencia Stuartii[3] Proteus mirabilis[3] Pseudomonas aerugnose[3] Serratia[3] Staphytcoccus albus[3] Staphytcoccus aureus[3,42,53] Methicillin –R.S.aureus[34, 46] Staphytcoccus group D [3] Staphytcoccus mits[3] Staphytcoccus pyogenes[3] Staphytcoccus salivarus[3] Vibrio Cholera[67] AgNP Enterococcus faecali [53] VibrioCholera[29 ] Vanomycin –R E faecium[34, 53] EscherichiaColi[37,34, 49,50,53] Escherichia Coli GFP[31] Escherichia Coli O157:H8[32] Ampicillin R E coli[60] Kiebsielia pneumonia[61] ESBL-RK pneumoniae[34, 53] 98 HIV[64] Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Pseudomonas aerugnose[37,34, 53] Salmonella typhi[15, 62] Staphytcoccus aureus[32,34,50,60,61] MRS. Epidermidis[31] Vibrio Cholera[37] Nitrifying bacteria[4] Bacillus subtiles[49,50] E.coliMTCC 443[40] E. coli MTCC 739[40] B. subtilis MTCC 441[40] S. aureus NCIM 5021[40] S. aureus NCIM 5021[40] Cu and Ag Hartmannella ionization vermiforrnis [69] Naegleria fowleri[69] Tetrahymena pyriformis[69] Ag/Al2O3 SARS water Coronavir us[73] AgZn Bacillus anthracts[47] Zeolite AgNP TiO2 Micrococcus lyfae[63] AgCl Nitrifying bacteria[4] Colloids Bacillus cereus[47] Bacillus subtiles[47] Staphytcoccus mits[66] AgBRNP Bacillus cereus[48] polymer composite Escherichia Coli[48] Pseudomonas aerugnose[48] 99 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD Methicillin –R.S.aureus[48] Fe3O4@Ag Bacillus subtiles[51] NPs Escherichia Coli[51] Staphytcoccus-epidermis[51] AgNP Bacillus subtiles[52] polymer films Pseudomonas aerugnose[63,52] Staphytcoccus aureus[64,52] Staphytcoccus-epidermis[64] Ag – Escherichia Coli[55.56] activated carbon fibers/ AgNP – granular activated carbon AgNP rice Escherichia Coli[57] paper plant Canodida albicans[57] stem Ag+ ions in Escherichia Coli[58] ceramics AgNP Pseudomonas aerugnose[65] ceramic beads Sphingomones[53] Staphytcoccus aureus[65] Aspergillus Murine niger[65] Norovirus[ 72] Polyethersul Canodida Reovirus[5 albicans[65] 8] Escherichia Coli[59] phone membranes 100 Asian Journal of Biochemical and Pharmaceutical Research Issue 4 (Vol. 4) 2014 CODEN(USA) : AJBPAD with AgNP in multilayers AgNPs on Listeria monocytogenes[62] paper silicone AgNP Aspergillus hydrogel niger[68] Canodida albicans[68] Ag– Pichia activated pastons[68] carbon fibers Saccharomyces cerevisiae[54] Silica-galss E. coli MTCC 443, a B. subtilis MTCC /SNP Hybrid 441[74 ] E. coli MTCC 739 [74 ] B. subtilis MTCC 441 [74] REFERENCES 1. 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