alginate Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colou ...

dressing is a natural wound dressing derived from carbohydrate sources released by clinical bacterial species, in the same manner as

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

formation. These types of dressings are best used on wounds that have a large amount of

exudate An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...

. They may be used on full-thickness burns, surgical wounds, split-thickness graft donor sites, Mohs surgery defects, refractory decubiti, and chronic ulcers. They can also be applied onto dry wounds after

normal saline Saline (also known as saline solution) is a mixture of sodium chloride (salt) and water. It has a number of uses in medicine including cleaning wounds, removal and storage of contact lenses, and help with dry eyes. By injection into a vein it ...

is first applied to the site of application. Alginate dressings are produced from the calcium and sodium salts of alginic acid, a polysaccharide comprising mannuronic and guluronic acid units. Alginate is initially extracted from the

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...

Brown seaweeds Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and po ...

. Alginate dressings can be in the form of freeze-dried, porous (foam) sheets or flexible fibres. Flexible fibres are used to treat cavity wounds. The alginate will form a gel in contact with the exudates of the wound and give it a strong absorbent power. There is no evidence of superior effectiveness in those with

diabetic foot ulcer Diabetic foot ulcer is a major complication of diabetes mellitus, and probably the major component of the diabetic foot. Wound healing is an innate mechanism of action that works reliably most of the time. A key feature of wound healing is stepw ...

Properties of alginate dressings

The gelling properties of alginates are attributed to the presence of

calcium ions Calcium ions (Ca2+) contribute to the physiology and biochemistry of organisms' cells. They play an important role in signal transduction pathways, where they act as a second messenger, in neurotransmitter release from neurons, in contractio ...

that help form a slow degradeable cross-linked polymer gel. Once in contact with an exuding wound, an ion-exchange reaction takes place between the calcium ions in the dressing and sodium ions in serum or wound fluid. When a significant proportion of the calcium ions on the fibre have been replaced by

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

, the fibre swells and partially dissolves forming a gel-like mass. The gel formed is highly hydrophilic, which limits wound secretions and minimizes bacterial contamination. Alginates rich in mannuronate form soft gels while those rich in guluronic acid form firmer gels with a higher absorbency of the exsudates.

Wound healing properties

Calcium alginate Calcium alginate is a water-insoluble, gelatinous, cream-coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate. Calcium alginate is also used for entrapment of enzymes and forming artif ...

dressings may help the production of mouse

fibroblasts A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells o ...

and ''in vitro'', of human fibroblasts.

Fibroblasts A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells o ...

are known to be involved in the regeneration and healing of the tissues. * It has been shown that

calcium alginate Calcium alginate is a water-insoluble, gelatinous, cream-coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate. Calcium alginate is also used for entrapment of enzymes and forming artif ...

activates human macrophages to produce

TNFα Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolog ...

(Tumor Necrosis Factor α) which is involved in the inflammatory signals and consequently

wound healing Wound healing refers to a living organism's replacement of destroyed or damaged tissue by newly produced tissue. In undamaged skin, the epidermis (surface, epithelial layer) and dermis (deeper, connective layer) form a protective barrier again ...

process. * Moreover, the

clotting Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

mechanisms during the first stage of wound healing may be improved by

. * A comparative study of

hydrocolloid dressing A hydrocolloid dressing is an opaque or transparent dressing for wounds. A hydrocolloid dressing is biodegradable, breathable, and adheres to the skin, so no separate taping is needed. The active surface of the dressing is coated with a cross-l ...

s and alginates showed that alginates gels remain on the wound for a longer period than hydrocolloids. * The early use of alginates as haemostats and wound dressings and their apparent lack of toxicity are discussed.

Uses

Alginate dressings are useful for moderate to heavily exuding wounds. In the form of fibres trapped in a wound, alginate is readily biodegradable and can be rinsed away with saline irrigation. Subsequent removal therefore, does not destroy granulation tissue, making dressing change virtually painless. The ease of biodegradation is exploited in making alginate sutures used in surgical wound closures. Since alginate dressings require moisture to function effectively, they cannot be used for dry wounds and those covered with hard necrotic tissue. This is because it could dehydrate the wound, delaying healing and this is their major disadvantage.

References

{{DEFAULTSORT:Alginate Dressing Medical dressings

Properties of alginate dressings

Wound healing properties

Uses

See also

References