Past observations and recent studies using a pure silver delivery system have demonstrated an increased rate of healing in wounds and burns compared to other wound care products.

The direct healing effect of pure silver has yet to be defined. Silver has a number of effects which would indirectly increase healing, namely controlling infection, decreasing excess inflammation, maintaining moist healing and decreasing wound surface mechanical trauma caused by frequent dressing changes.

Mechanisms for Pro-Healing Effect of nanocrystalline Silver

• Direct effect in wound biology
• Controlling surface microbes
• Moist wound healing maintained
• Decreasing mechanical trauma during dressing changes
• Decreasing excess wound inflammation

1. Direct Effect of Silver on Healing

Silver has a number of biological effects on the wound surface.  It remains to be determined whether any of these effects produces a healing stimulus.

Several studies comparing silver released from a silver nanocrystal delivery system with other topical antibiotics have demonstrated increased re-epithelialization of partial thickness wounds and meshed skin grafts.  A comparison was made of the rate of re-epithelialization of 2:1 meshed skin grafts on excised burn wounds.  The nanocrystal silver group re-epithelialized at a significantly faster rate.  No infection was noted in either group, both using moist wound healing.

Methods:

• 20 burn patients with bilateral extremity burns

• Excised and covered mesh graft (2:1)
• One group skin graft covered with Acticoat™
• Other group skin graft kept moist using Neosporin solution

2. Controlling Surface Microbes

Increasing evidence has demonstrated that wound colonization can result in a bacterial burden to healing.  The concept that one needs 10⁵ organisms per gram of tissue to be deleterious is no longer considered accurate.  Certainly 10⁵ organisms or greater is destructive to healing but fewer bacteria can also impede healing as the immune defenses of a wound and of a patient vary considerably, e.g. the elderly diabetic versus the healthy young adult.

Improved antimicrobial activity should therefore assist healing independent of any direct healing property of silver.

3. Maintaining Moist Wound Healing

Numerous studies followed which demonstrated that wound occlusion and moisture improved all phases of healing.  The data demonstrating that a moist wound surface increases re-epithelialization and all other components of wound healing is now well established.  Any surface desiccation leads the risk of further tissue damage.

• Increased depth of surface tissue necrosis
• Impediment to surface epithelial cell migration
• Decreased surface oxygen available for healing and bacterial killing
• Impaired nutrient flow to surface
• Increased infection risk

In general, research has shown that a moist wound environment is associated with less severe and prolonged inflammation; more rapid keratinocyte proliferation and migration; earlier differentiation of keratinocytes to restore surface barrier function; more rapid fibroblast proliferation, increase in collagen synthesis; earlier, angiogenesis; and earlier full-thickness wound contraction.  A more rapid decrease in wound volume and surface area has also been well documented with moisture.

This use of a moist healing environment has not routinely been used in burns because of the concern for infection.  Also the antibiotic creams do not produce a moist healing environment.  In fact, the creams silver sulfadiazine and sulfamylon, will extract water from the wound surface as a result of the hyperosmolarity of the cream, especially with drying of the cream.

• Reduction in wound surface conversion
• Decrease in surface desiccation and eschar formation
• Increase in local growth factor production
• Activation of surface proteases to remove devitalized tissue
• Decreased surface inflammation
• Enhanced wound surface immune defenses
• Increased rate of angiogenesis and fibroblast proliferation
• Increased proliferation and migration of epithelial cells along thin water layer

The nanocrystal silver delivery system maintains a moisture layer between the wound surface and the inner silver membrane.  This moisture layer is also a potent antimicrobial silver solution on the wound surface.  Moisture is maintained on a deep burn by wetting the surface of the Acticoat™.  Moisture on a partial thickness wound is provided by the wound itself under the Acticoat, which is covered with a secondary dressing. 

The ability to maintain both a moist healing environment and an antimicrobial environment is a unique property of this silver system, especially beneficial for burns and wounds.

4. Decreasing Mechanical Trauma

Frequent dressing change and wound manipulation create not only systemic toxicity but also local wound trauma.  The high rates of bacteremias with wound manipulation have been well described as has the typical pyrogen release and post-dressing change hyperthermia.  Also wound surface manipulation especially on the re-epithelial zing wound will injure new tissue formation Mechanical removal of creams, ointments and dressings will all cause local trauma.  The nanocrystalline silver dressing can remain in place for days and if wetted prior to removal, mechanical trauma is minimal.  In addition, the exudates beneath is usually minimal and there is no film or byproduct, which requires mechanical removal.