Silver Sustained Release Antibacterial Technology

The topical antimicrobial agent silver has been used for hundreds of years in wound care. For example, silver has been used to prevent or manage infection in its solid elemental form (eg silver wire placed in wounds), as solutions of silver salts used to cleanse wounds (eg silver nitrate solution), and more recently as creams or ointments containing a silver–antibiotic compound (silver sulfadiazine (SSD) cream). 1

In metallic (elemental) form, silver is unreactive and cannot kill bacteria. To become bactericidal, silver atoms (denoted as Ag or Ag0) must lose an electron and become positively charged silver ions (Ag+). Elemental silver ionises in air, but ionises more readily when exposed to an aqueous environment such as wound exudate. In contrast, silver compounds contain positive silver ions bound to negatively charged ions or molecules. When exposed to aqueous environments, some of the silver ions become detached from the compound.

Silver ions are highly reactive and affect multiple sites within bacterial cells, ultimately causing bacterial cell death. They bind to bacterial cell membranes, causing disruption of the bacterial cell wall and cell leakage. Silver ions transported into the cell disrupt cell function by binding to proteins and interfering with energy production, enzyme function and cell replication. Silver ions are active against a broad range of bacteria, fungi and viruses, including many antibiotic-resistant bacteria, such as meticillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE).

Biofilms are complex microbial communities, containing bacteria and sometimes also fungi, which are embedded in a protective polysaccharide matrix. The matrix attaches the biofilm to a surface, such as a wound bed, and protects the microorganisms from the host's immune system and from antimicrobial agents such as antiseptics and antibiotics. Biofilms are commonly present in chronic wounds, and are thought to contribute to, and perpetuate, a chronic inflammatory state that prevents healing. 2

Currently, the management of biofilms involves:
· Reduction of biofilm burden through debridement and/or vigorous cleansing to remove the biofilm and the dormant (persister) bacteria.
· Prevention of biofilm reformation through the use of topical antimicrobials to kill planktonic (free-floating) bacteria.

Studies of the effects of silver dressings on experimental models of biofilms have suggested that silver may reduce bacterial adhesion and destabilise the biofilm matrix, as well as kill bacteria within the matrix and increase susceptibility of bacteria to antibiotics. Many studies have confirmed this point, but further research is needed for a clearer mechanism.

Anti-Biofilm Activity
Some laboratory studies have suggested that silver may have beneficial effects on wound healing other than the control of bioburden alone. For example, silver nitrate, nanocrystalline silver, and some silver-containing dressings have been found to have anti-inflammatory effects and to encourage blood vessel formation (neovascularisation). The clinical relevance of these findings is not yet known.

The use of silver dressings can effectively alleviate the dependence of clinical nursing on antibiotics and make more choices in the treatment of wound infection. FORYOU MEDICAL will continue to study silver antimicrobial dressings and other antibacterial products in order to contribute to the fight against bacterial resistance.
For you, for us, for life !

1. International consensus. Appropriate use of silver dressings in wounds. An expert working group consensus. London: Wounds International, 2012 Available to download from: www.woundsinternational.com

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