WHAT ARE THE BIOLOGIC PROPERTIES OF SILVER RELATED TO WOUND INFECTION CONTROL AND HEALING

Silver has long been known to be a potent antimicrobial agent and its beneficial effects on wound biology have in general been overlooked until recently. A description of what silver does and its role in wound management will be presented briefly with a more complete discussion in later sections.

ANTIMICROBIAL PROPERTIES:

The antimicrobial activity of silver ion is well defined. Silver ion rapidly kills microbes by blocking the cell respiration pathway. The speed of action is almost instantaneous once the silver reaches the microbe. The efficacy of microbe killing is based not only on the amount of silver ion present, but likely also the presence of other silver radicals generated by a silver releasing product.
Because of mechanism of action, microbial resistance to silver itself has not been reported. In addition, silver has repeatedly been shown to be non-toxic to human cells. Toxicity occurs from the complexes used to deliver silver such as nitrate and sulfadiazine.

Infection Control ( Antimicrobial Properties )

kills microbes on contact by poisoning microbe cellular respiration speed of action directly correlated with the silver ion dose in contact with microbes silver resistance is not seen safe and non-allergenic

Silver ion is known to have the following biochemical effects on a wound:

Histologically decreases wound surface inflammation Decreases wound surface excess metalloproteinase activity likely by decreasing zinc, essential for metalloproteinase (MMP) activity Oxidizes and binds to sulfur bonds, unlike Zinc and Copper which bind to oxygen. Sulfur bonds are necessary for MMP activity Increase in wound calcium (a pro epithelialization effect)

 

Section II.

WHAT ARE THE BIOLOGIC PROPERTIES OF SILVER RELATED TO WOUND INFECTION CONTROL AND HEALING

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(THE FACTS ABOUT SILVER)

Silver has long been known to be a potent antimicrobial agent and its beneficial effects on wound biology have in general been overlooked until recently. A description of what silver does and its role in wound management will be presented briefly with a more complete discussion in later sections.

ANTIMICROBIAL PROPERTIES:

The antimicrobial activity of silver ion is well defined. Silver ion rapidly kills microbes by blocking the cell respiration pathway. The speed of action is almost instantaneous once the silver reaches the microbe. The efficacy of microbe killing is based not only on the amount of silver ion present, but likely also the presence of other silver radicals generated by a silver releasing product.
Because of mechanism of action, microbial resistance to silver itself has not been reported. In addition, silver has repeatedly been shown to be non-toxic to human cells. Toxicity occurs from the complexes used to deliver silver such as nitrate and sulfadiazine.

Infection Control ( Antimicrobial Properties )

kills microbes on contact by poisoning microbe cellular respiration speed of action directly correlated with the silver ion dose in contact with microbes silver resistance is not seen safe and non-allergenic

Silver ion is known to have the following biochemical effects on a wound:

Histologically decreases wound surface inflammation Decreases wound surface excess metalloproteinase activity likely by decreasing zinc, essential for metalloproteinase (MMP) activity Oxidizes and binds to sulfur bonds, unlike Zinc and Copper which bind to oxygen. Sulfur bonds are necessary for MMP activity Increase in wound calcium (a pro epithelialization effect)

Wound Healing Properties:

The anti-inflammatory effects of silver ion on a wound have been recognized for centuries. Most of the reports are purely descriptive in nature identifying the decrease in erythema and increased healing.
A number of the biochemical effects of silver on the wound have been documented over a decade ago. However, only recently with the new concepts on wound healing and healing impairment, can a mechanism of action be presented. The major focus of wound healing has been on the relationship between tissue destruction by a group of collagenase enzymes known as METALLOPROTEINASES (MMP) and tissue synthesis which is stimulated by growth factors.

CURRENT CONCEPTS

• An excess of MMP activity has been reported in burn wounds and in chronic wounds.
• Action of the MMP’s is dependent on the availability of free Zinc.
• Silver decreases surface Zinc which could decrease excess MMP activity and increasing healing rate.
• Recent findings indicate that silver (as delivered by the pure silver system ACTICOAT) decreases MMP activity.
• The fact that silver increases wound surface calcium should stimulate epithelialization.

A more detailed description will be presented later.

Wound Healing (Wound Surface Effects)

• decreases wound surface excess inflammation (anti-inflammatory)
• decreases metalloproteinase MMP activity present which is excessive in burns and chronic wounds likely by decreasing zinc
• increases wound calcium - a pro healing effect

ACTION OF SILVER ION ON BURN WOUND

Decreases Zn+ on surface Decreases excess MMP (Metalloproteinase) activity Increases Ca+ on surface which increased epithelialization Anti-inflammatory

Effect of silver delivery (ACTICOAT) on Metalloproteinase (Collagenase) MMP 1.8.13

A quantitative assay was undertaken using collagenase MMP-1, MMP-8; and MMP-13). As MMP-2 and MMP-9 have related activities (gelatinase), they are anticipated to behave similarly and produce results similar to those obtained for the collagenase tested.
The collagenase inhibition test was conducted by adding dilutions of ACTICOAT dressing extract (3 sq. in. in 5 ml. Water) to an assay mixture containing fluorescently-labeled gelatin and appropriately diluted (in water) collagenase. Following incubation the activity of the enzyme was compared to baseline activity (no inhibitor). The assay was also conducted in the presence of a known inhibitor (0.5 mM phenanthroline). The inhibitor reduced enzyme activity by 70%. The silver related from ACTICOAT reduced enzyme activity by 90%.