Antimicrobial Agent: Prevents Bacterial Growth
Research (Spectrum of Antimicrobial Activity Associated with Ionic Colloidal Silver, Volume: 19 Issue 3: March 20, 2013) carried out in the Department of Naturopathic Research at Southwest College of Naturopathic Medicine in Tempe, Arizona examined how effective colloidal silver is in eliminating bacteria, fungi, and viruses. The researchers grew several strains of each microbe, with and without the addition of colloidal silver. The results showed that the presence of colloidal silver inhibited (reduced) bacterial growth. In regard to the fungi, the effect of silver varied with the specific strain. The silver had no effect on viral growth.
Italian researchers investigated the effect of colloidal silver on biofilm-associated infections, bacterial strains that grow at the site of a medical implant and the main reason why such implants are not successful. As more and more people need and receive such implants, the health profession is interested in finding solutions to increase the success of these procedures. The Italian researchers found that implants with a nanosilver coating were significantly more effective in preventing biofilm infections.
Many patients require tissue-engineering scaffolds, medical devices that help the patient grow new skin. Examples include severe burns victims or patients with bedsores resistant to other healing methods. In order for this scaffolding to work, it must be antibacterial so the new tissue does not get infected from the get-go. A group of Hong Kong scientists investigated whether or not the presence of nanosilver is helpful against such infections. They used a common scaffolding material, degradable (dissolvable) poly-L-lactide (PLLA). They added nanosilver (Ag) to it, then divided the resulting Ag/PLLA solution into several parts. To each of the parts, they added a common strain of bad bacteria: Escherichia coli (E. coli) to one and Staphylococcus aureus (Staph.) to another. The samples were then left to incubate. When checked, there were clearly marked no-grow zones in both samples. Those that did not contain silver exhibited bacterial growth as expected.
AgNPs have a good silver ion release ability, which makes them attractive for the development of antimicrobial biomaterials. In most cases, the size of silver particles was shown to be important.
There are several silver categories:
- metallic silver coatings
- silver-containing nanocomposites
- silver-containing polymers
- surface modification with ionic silver compounds
- hybrid silver materials
Silver has been intensively studied over recent decades for the prevention and treatment of infections on burns, prostheses, catheters, vascular grafts, surgical instruments, and dental devices. One special advantage of using silver-containing materials to coat biomaterials, besides its biocompatibility and antimicrobial activity, is that they may protect both the inner and outer surfaces of the device and its proximity; the coating does not always need to cover the whole implant surface in order to protect an implant from a possible infection.
Some studies suggest that materials containing silver ions or AgNPs have better antimicrobial activity than metallic silver coatings. This is likely true, due to a higher rate of silver ions delivered from the nanoparticles.
In some studies, bacterial growth was regenerated after three or four days. Two possible reasons for this are that the device may have contained only a little silver, as compared to the speciﬁcations. It was likely that the particles were too large, about 500nm in diameter, for efficient silver ion release, or else some were buried too deep to be accessible.
Textiles and fabrics are recognized as an ideal medium for microbial development. Silver nanoparticles are recognized as a smart component to use in fabrics such as polyester or cotton. Research suggests that embedding silver within fabrics and polymers can impregnate and stabilize the AgNPs so they can retain their antimicrobial activity for a longer time and, thus, prevent further microbial development. This application is of great interest for the fabrication of antimicrobial bandages or silver-impregnated clothing. Biodegradable coatings or impregnation methods may also be valuable in a controlled release of antimicrobial silver ions.
It has also been demonstrated that silver treatment of stainless steel surfaces can be accomplished through a process called double-glow plasma alloying technology, producing a beneficial stainless steel antibacterial material. This process results in a harder stainless steel, one with improved wear and tear resistance. The material can also be highly beneﬁcial for load-bearing implants that are prone to surface damage.
Silver supports wound healing by maintaining a germ-free area in a moist, wound-healing environment. Silver dressings are frequently used with much success. Silver products, like silver nitrate, silver sulfadiazine [(4-aminophenyl) sulfonyl] (pyrimidin-2-yl)-azanide) are widely used as antimicrobial agents today.
Destroyer of Multidrug-Resistant Bacteria
More and more antibiotic-resistant microbes are developing. Since antibiotics are the current weapon of choice to treat bacterial infections, this is quite worrying. Thus, much interest has been focused on colloidal silver as a viable alternative.
An article in The International Journal of Microbiological Research appears to support the use of colloidal silver in this area. The study, carried out in Egypt, showed that nanosilver had a significant bactericidal (bacteria-killing) effect on E. coli, Staph., Salmonella typhi (S. typhi), and Pseudomonas aeruginosa (P. aeruginosa), some of the more harmful strains around today. Also, nanosilver was found to be highly effective against multidrug-resistant, Gram-positive and -negative bacterial strains.
Colloidal Silver Conclusion 9: Colloidal silver functions both an as antimicrobial agent (preventing growth) and as an effective bactericide (killer of bacteria), an alternative to antibiotics in cases of drug-resistant bacteria.
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