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Silver nanoparticles

Silver nanoparticles are nanoparticles of silver, i.e. silver particles of between 1 nm and 100 nm in size. While frequently described as being 'silver' some are composed of a large percentage of silver oxide due to their large ratio of surface to bulk silver atoms.

[] Synthesis

There are many different synthetic routes to silver nanoparticles. They can be divided into three broad categories: physical vapor deposition, ion implantation, or wet chemistry.

[] Ion implantation

Although it may seem counter-intuitive, ion implantation has been used to create silver nanoparticles.^[1] This process has been shown to produce silver particles embedded in polyurethane, silicone, polyethylene, and polymethylmethacrylate. The particles grow in the substrate with the bombardment of ions. The existence of nanoparticles is proven with optical absorbance, though the exact nature of the particles created with this method is not known.

[] Wet chemistry

There are several wet chemical methods for creating silver nanoparticles. Typically, they involve the reduction of a silver salt such as silver nitrate with a reducing agent like sodium borohydride in the presence of a colloidal stabilizer. Sodium borohydride has been used with polyvinyl alcohol, poly(vinylpyrrolidone), bovine serum albumin (BSA), citrate and cellulose as stabilizing agents. In the case of BSA, the sulfur-, oxygen- and nitrogen-bearing groups mitigate the high surface energy of the nanoparticles during the reduction. The hydroxyl groups on the cellulose are reported to help stabilize the particles. Citrate and cellulose have been used to create silver nanoparticles independent of a reducing agent as well. An additional novel wet chemistry method used to create silver nanoparticles took advantage of ß-D-glucose as a reducing sugar and a starch as the stabilizer.

Also, it is important to note, not all nanoparticles are created equal. The size and shape have been shown to have an impact on its efficacy. Additionally, crystal facet size, oxide content and several other factors could also affect the antimicrobial properties.

[] Uses

See also: Medical uses of silver

Over the last decades silver nanoparticles have found applications in catalysis, optics, electronics and other areas due to their unique size-dependent optical, electrical and magnetic properties.^[2] Currently most of the applications of silver nanoparticles are in antibacterial/antifungal agents in biotechnology and bioengineering, textile engineering, water treatment, and silver-based consumer products.^[3]

There is also an effort to incorporate silver nanoparticles into a wide range of medical devices, including but not limited to

• bone cement,
• surgical instruments,
• surgical masks,
• wound dressings.
• treatment of HIV-1. "In the first-ever study of metal nanoparticles' interaction with HIV-1, silver nanoparticles of sizes 1-10nm attached to HIV-1 and prevented the virus from bonding to host cells. The study, published in the Journal of Nanotechnology, was a joint project between the University of Texas, Austin and Mexico University, Nuevo Leon."^[4]

Samsung has created and marketed a material called Silver Nano, that includes silver nanoparticles on the surfaces of household appliances.

Silver nanoparticles have been used as the cathode in a silver-oxide battery.

[] Health Concerns

The neutrality of this section is disputed. Please see the discussion on the talk page. Please do not remove this message until the dispute is resolved. (August 2009)

Ionic silver has a long history of use in topical medical applications, and it has been shown that ionic silver, in the right quantities, is suitable in treating wounds.^{[5][6][7][8][9]} According to Atiyeh et al. (2007), "The gold standard in topical burn treatment is silver sulfadiazine (Ag-SD), a useful antibacterial agent for burn wound treatment".^[10] The US Food and Drug Administration has approved the use of a range of different silver-impregnated wound dressings.^[11] Silver nanoparticles are now replacing silver sulfadiazine as an effective agent in the treatment of wounds.^[10][12]

• Allergic Reaction: While there is anecdotal evidence suggesting the possibility of a silver allergy, an extensive review of the medical literature does not lend any credence to this possibility ^[13]. Some silver alloys that include nickel do elicit an allergic reaction.

• Argyria and Staining: Ingested silver or silver compounds, including colloidal silver, can cause a condition called argyria, a discoloration of the skin and organs.In 2006, there was a case study of a 17-year-old man, who sustained burns to 30% of his body, and experienced a temporary bluish-grey hue after several days of treatment with Acticoat, a brand of wound dressing containg silver nanoparticles.^[14] Argyria is the deposition of silver in deep tissues, a condition that cannot happen on a temporary basis, raising the question of whether the cause of the man’s discoloration was argyria or even a result of the silver treatment ^[15]. Silver dressings are known to cause a “transient discoloration” that dissipates in 2–14 days, but not a permanent discoloration.^{[citation needed]}

• Silzone heart valve: St. Jude Medical released a mechanical heart valve with a silver coated sewing cuff (coated using ion beam-assisted deposition) in 1997 ^[16]. The valve was designed to reduce the instances of endocarditis. The valve was approved for sale in Canada, Europe, the United States, and most other markets around the world. In a post-commercialization study, researchers showed that the valve prevented tissue ingrowth, created paravalvular leakage, valve loosening, and in the worst cases explantation. After 3 years on the market and 36 000 implants, St. Jude discontinued and voluntarily recalled the valve.

[] References

1. ^ Stepanov, A L, V N Popok, and D E Hole. "Formation of Metallic Nanoparticles in Silicate Glass." Glass Physics and Chemistry 28, no. 2 (March 2002): 90-95.
2. ^ Khaydarov, R.A., Khaydarov, R.R., Gapurova, O., Estrin, Y., and Scheper, T. (2009) “Electrochemical method of synthesis of silver nanoparticles”, Journal of Nanoparticle Research, Vol. 11(5), pp. 1193-1200 | doi=10.1007/s11051-008-9513-x
3. ^ Khaydarov, R A., Khaydarov, R R., Gapurova, O. & Estrin, Y. (2010). A novel method of continuous fabrication of aqueous dispersions of silver nanoparticles. Int. J. Nanoparticles, 3, pp. 77-91 | doi=10.1504/IJNP.2010.033223
4. ^ http://74.125.95.132/search?q=cache:_EvMXLKqIkIJ:www.space-age.com/NanoSilverHIV.doc+can+sulfur+kill+a+virus&cd=1&hl=en&ct=clnk&gl=us
5. ^ http://www3.interscience.wiley.com/journal/118718782/abstract
6. ^ http://www.theengineer.co.uk/Articles/299472/Combatting%20the%20bug.htm
7. ^ http://tahilla.typepad.com/mrsawatch/wounds_silver/
8. ^ Hermans MH (2006). "Silver-containing dressings and the need for evidence". The American journal of nursing 106 (12): 60–8; quiz 68–9. PMID 17133010. 
9. ^ http://jac.oxfordjournals.org/cgi/content/full/dkm006v2
10. ^ ^{a b} Atiyeh BS, Costagliola M, Hayek SN, Dibo SA (2007). "Effect of silver on burn wound infection control and healing: review of the literature". Burns 33 (2): 139–48. doi:10.1016/j.burns.2006.06.010. PMID 17137719. 
11. ^ http://www.accessdata.fda.gov/Scripts/cder/DrugsatFDA/index.cfm?fuseaction=Search.DrugDetails
12. ^ Lansdown AB (2006). "Silver in health care: antimicrobial effects and safety in use". Current Problems in Dermatology 33: 17–34. doi:10.1159/000093928. PMID 16766878. 
13. ^ Homstrup, Palle. "Reactions of the oral mucosa related to silver amalgam: a review." Journal of Oral Pathology & Medicine 20, no. 1 (January 1991): 1-7.
14. ^ Trop, Marji, Michael Novak, Siegfried Rodl, Bengt Hellbom, Wolfgang Kroell, and Walter Goeseeler. "Silver-coated dressing acticaot caused raised liver enzymes and argyris-like symptoms in burn patient." The Journal of Trauma, Injury, Infection and Critical Care, 2006: 648-652.
15. ^ Parkes, A. "Silver-coated dressing Acticoat." J. Trauma 61, no. 1 (July 2006): 239-40.
16. ^ Horstkotte, Dieter. "Thrombogenicity of the St. Jude Medical Prosthesis with and without silzone-Coated Sewing cuffs." Ann Thorac Surg 71 (2001): 1065-73.