AQUACEL® Ag dressings (Box 1) incorporate Hydrofiber® Technology with 1.2% (w/w) silver (ie 12mg of silver per gram of dressing). The combination of Hydrofiber® Technology with ionic silver (Ag+) produces a dressing that is highly absorbent, has favourable gelling characteristics (Box 2) and broad-spectrum antimicrobial activity (as demonstrated by in vitro testing)1-3. These qualities mean that AQUACEL® Ag dressings can assist in overcoming major challenges to wound healing.

Authors: Queen D, Walker M, Parsons D, Rondas A.


AQUACEL® Ag is a versatile primary dressing indicated for moderate to highly exuding chronic and acute wounds where there is infection or an increased risk of infection. AQUACEL® Ag Ribbon Dressing with Strengthening Fiber is suitable for cavity wounds and AQUACEL® Ag SURGICAL cover dressing is used on surgical incisions (Box 1).


How are AQUACEL® Ag dressings made?
AQUACEL® Ag dressings are made using patented Hydrofiber® Technology processes (Box 2). The even distribution of ionic silver permits antimicrobial activity; while the silver deeper within the dressing acts as a reservoir to provide sustained silver availability[3,4].

AQUACEL® Ag Ribbon Dressing with Strengthening Fiber is made from strips of silver impregnated Hydrofiber® Technology that have been stitch-bonded with a non-gelling yarn. The yarn reinforces the ribbon dressing to provide tensile strength even when the dressing is wet.

AQUACEL® Ag SURGICAL cover dressing is made by layering an island of silver-impregnated Hydrofiber® Technology with a hydrocolloid adhesive layer and a breathable polyurethane film backing. The Hydrofiber® island is stitch-bonded with nylon and elastane yarns to provide mor

e flexibility if the dressing is placed over joints. The hydrocolloid layer allows adhesion to the skin and the polyurethane film acts as a waterproof bacterial barrier.

Managing exudate
A key feature of dressings made with Hydrofiber® Technology is their ability to lock in any fluid that is absorbed5 (Box 2). This means that wound exudate, and the pathogenic bacteria and harmful enzymes that it may contain[6,11], are removed from the wound bed. As a result, the wound surface and surrounding skin are protected from potentially harmful effects[9,10]. In addition, when the dressing is removed from the wound, the trapped bacteria and enzymes are also removed, meaning that any release of bacteria from the dressing into the air is minimised.

In acute healing wounds and in chronic wounds, dressings made with Hydrofiber® Technology maintain a moist wound environment whilst absorbing excess exudate[12]. In partial thickness wounds (eg burns), animal studies have shown that neutrophils are taken up into dressings containing Hydrofiber® Technology and a layer of fibrin forms between the dressing and the wound[7]. The fibrin aids adhesion of the dressing to the wound, enhancing conformability and reducing dead space. In addition, the uptake of neutrophils into the dressing in combination with the fibrin layer may prevent interaction of these immune cells with macrophages and so reduce the inflammatory response[7].

Antimicrobial properties
AQUACEL® Ag dressings contain ionic silver and provide sustained and effective antimicrobial activity against a wide range of aerobic, anaerobic (including antibiotic resistant strains such as methicillin-resistant Staphylococcus aureus [MRSA] and vancomycin-resistant enterococci [VRE]), yeast and filamentous fungi for up to 14 days, as demonstrated by in vitro testing[3,13]. AQUACEL® Ag dressings may be left in place for up to seven days in chronic wounds14 or for up to 14 days on partial thickness burns[13]. The ionic silver in AQUACEL® Ag dressing starts killing a broad spectrum of pathogens, including MRSA, within 30 minutes of exposure to the dressing3. In addition, bacteria absorbed into the dressing are also destroyed[1,15]. AQUACEL® Ag dressings also control bioburden by micro-contouring to the wound bed (Box 2) to prevent dead spaces where bacteria may flourish and to ensure delivery of the antimicrobial ionic silver directly where needed ((as demonstrated by in vitro testing).

Why is ionic silver important?
High silver content or the total amount of silver made available by a dressing does not relate directly to greater antimicrobial activity8. This is because silver exists in several chemical forms. Silver metal (Ag) can only become effective as an antimicrobial agent when it transforms into silver ions (Ag+).

Silver ions damage bacterial cell walls and interfere with DNA synthesis. Silver ions also denature proteins and enzymes, and inhibit protein synthesis, killing the bacterium[16]. This multi-targeted mechanism of action means that ionic silver has a far lower propensity to induce bacterial resistance than classic antibiotics[17].

AQUACEL® Ag dressings contain silver only in the ionic form (Ag+). The dressings act as a reservoir of silver ions by continually supplying a concentration that has effective antimicrobial action[3,4], while avoiding higher concentrations that may cause transient skin staining as seen during in vitro testing[18].

AQUACEL® Ag dressings make ionic silver available in a controlled manner in response to exudate levels, ie 'on demand'[3]. The amount of ionic silver available is limited by the maximum amount of silver ions that can get into solution, ie if exudate levels increase or ionic silver is consumed by antimicrobial action, the concentration of silver ions in the exudate drops and the dressing will release more to re-establish the maximum solution concentration[3].
Because the silver ions are readily available and easily dissociated from the strands of Hydrofiber®  Technology, the dressings do not need to contain large amounts of silver to be able to produce sufficient concentrations of silver ions 'on demand' for antimicrobial action[3,4].