Since the 1990s, silver has been so frequently incorporated into advanced wound care dressings, silver-containing formats are now available in virtually the entire range of advanced wound dressings. But what is it that has made silver such a popular feature for wound care dressings?
The short answer is that silver works—something that has been known for a very long time. In past centuries, silver has been used in drinking and storage vessels to prevent spoilage. More recently, silver—and silver compounds such as silver sulphadiazine and silver nitrate—have been adopted by the medical community because of its ability to:
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Prevent infections
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Sterilize medical devices
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Discourage the formation of biofilms in heart valves, endotracheal tubes and catheters.

Yet, despite its popularity and versatility, the benefits claimed for silver in wound dressings—and the mechanisms that deliver these benefits—still maintain some controversy and will probably not be totally resolved in the near future.
An Atomic Appreciation of Silver
The active antimicrobial agent associated with silver is the positive silver ion (Ag+). This ion has an oligodynamic effect, meaning that extremely low concentrations are required.
The ion is short-lived and can be easily removed from a solution by combining it with negative ions (Cl-). The ion readily binds with many microbial structures, proteins and nucleic acids, enabling it to inactivate microbes by several different pathways at once. This is thought to greatly reduce the opportunity for infectious agents to develop resistance to the actions of silver, and it contributes to its broad spectrum of activity.
Getting the Silver Into Silver Wound Dressings
Silver is incorporated into wound dressings as elemental silver (e.g., Acticoat®, Silverlon®, MediPlus™ Foam Ag) or as a component of various silver salts (e.g., silver sulphadiazine, silver lactate).
To be effective, the silver element or compound must be moistened with water or exudate to release the silver ion. Elemental silver is not very soluble, so it must be presented over a large surface area (such as with fibers or nets) to insure the dissociation of a sufficient number of ions.
Silver salts vary in their dissociation constant and are easier to incorporate into foams, hydrocolloids and hydrogels. Silver dressings can contain a large reservoir of silver, allowing continuous replacement of ions as they are taken up by microbes and inactivated by other components of the wound fluid. The long-acting effect supports longer intervals between wound dressing changes and less disturbance of wound healing.
Silver Wound Dressing Studies and Toxicity
Silver wound dressing studies have compared the amounts of silver in a dressing and the rate of silver release in-vitro, but this kind of data often shows poor correlation with a dressing’s activity, suggesting that several variables are in play. Apparently, once effective levels of silver are reached, excess ions have little additional activity, and that speed of release is less important a factor in the time/dose effect than might be seen in the in-vitro studies.
In-vivo, however, the fluid and biological environment in which ions are released are vastly different. It would be anticipated that in-vitro ionization would be less than in an aqueous solution and that ion removal would be faster and greater. Sufficient levels of silver ion constantly replaced during use would appear to provide optimal performance.
The toxic effects of silver to human cells are well documented and understood. Many observations are based on high blood and tissue levels that may occur in burn patients where a large body area may be covered with silver sulfadiazine for extended periods. In most cases, silver is cleared from the body over time and without toxic effects. The amount presented for systemic absorption by advanced wound care dressings in considerably less.
Silver Wound Dressings and Bioburden Reduction
Although there are few randomized controlled studies that achieve statistical significance in showing a reduction in the infection rate associated with the use of silver wound dressings, ample clinical evidence indicates they are associated with reduction in pain, reduction in odor, and improved quality-of-life measures.
Silver-containing wound dressings have been shown to reduce wound complications and to reduce the occurrence of critical colonization when compared to the same materials without silver. Further, Silver wound dressings are associated with reduced inflammation, increased rate of healing and reduction in biofilm formation.
The observed benefits are thought to result from silver’s broad spectrum of antimicrobial activity helping to control bioburden. The antimicrobial action may provide benefit at the wound-dressing interface and within the dressing where fluid-containing pathogens are sequestered. Reduction in bioburden improves the wound-healing environment by reducing competition for resources and the production of toxic metabolites. With fewer pathogens present, inflammation due to critical colonization may be sufficiently reduced to allow the wound to progress unimpeded to the proliferative phase of healing.
With silver available in a large number of advanced wound care products, the selection of a wound dressing can be optimized for the type and condition of the wound, with the silver component providing the extra security derived from broad-spectrum antimicrobial activity. Reduction in bioburden may result in:
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Reduced inflammatory response (including a reduction in MMP generation and activity)
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Reduced exudation
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Reduced pain
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Removal of many of the factors that impede the healing of chronic wounds
In conclusion, silver dressings offer the health care professional a valuable tool for use in treating acute, chronic and difficult wounds. The availability of new cost-effective wound care products allows their benefits to be extended to a larger population of patients.
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Looking back approximately 100 years ago, it was an era when gauze was the first choice for wound care dressing. This era represents the first baseline and lengthiest plateau in the wound care dressing evolution.

As wound care dressing categories evolved, so did the role of dressing healing studies. Although these studies had always compared different wound care products from start of treatment to healing, they also began to indicate different product classes’ advantages for different stages of wound healing.
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