Calcium Alginate

Description

Calcium Alginate is the calcium salt of alginic acid, a natural polyuronide constituent of certain brown algae. Calcium alginate is prepared by the neutralization of purified alginic acid with appropriate pH control agents, or from sodium alginate by metathesis with appropriate calcium salts.
Alginate, a colloidal polyuronic acid structural molecule capable of gelation, is used in the preparation of colloidal biodegradable structures such as gels, biofilms, beads, nanoparticles, and microcapsules suitable for applications that range from gel based separation technologies to drug delivery and cell preservation.
Calcium alginate has been around for years. More recently, it has been added to wound gels, hydrocolloids, and cleansers. Silver, a known antimicrobial agent, also has been added to many wound products, including calcium alginate. Unadulterated calcium alginate comes in the form of a flat square or mat (in many sizes) or a rope. The ropes can be manipulated to fit easily in wound cavities. Although one of its stated uses is to provide homeostasis, calcium alginate is more commonly thought of as the dressing that can absorb 20 times its weight in exudate, soak up loose debris from the wound bed, provide an optimal environment for healing, and provide a painless dressing change. This study is a reminder that calcium alginate is a valuable tool in our wound care arsenal.

Chemical Properties

Calcium alginate is an odorless or almost odorless, tasteless, white to pale yellowish-brown powder or fibers.

Uses

Alginate is used in many applications and new ones are being found all the time. The uses range from applications in the food industry to wound dressings, medicines and dental impression materials.

1. Calcium alginate (the cross-linked polymer) is used in wound dressings. These dressings are particularly useful for slow healing wounds like leg ulcers, which can continue to bleed and weep for a long time. Part of the blood clotting mechanism involves calcium ions and on contact with blood the calcium alginate releases calcium ions in exchange for sodium ions – just as you observed in the experiment above. These extra calcium ions can help the blood to clot and encourage healing. It is easy to remove any excess calcium alginate when the dressing has to be changed.
2. Calcium alginate dressings with silver have been found to be safe and effective for use for leg ulcers.
3. Calcium alginate dressings are made from salts of alginic acid obtained from algae (Phaeophyceae sp.j found in seaweed. They are known for absorbing excess wound exudate and forming a non-adherent gel, which accelerates wound healing by promoting a moist wound healing environment, facilitating debridement, and helping to prevent trauma to the wound bed and the surrounding skin (Fanucci and Seese, 1991).
4. Calcium alginate dressings are used on moderate to heavily exudative wounds during the transition from debridement to repair phase of wound healing (Seymour, 1997, Joël et al., 2002). Dry wounds should not be treated with these dressings because they have no hydrating properties.

Production Methods

Calcium alginate can be obtained from seaweed, mainly species of Laminaria.
Solutions of sodium alginate interact with an ionized calcium salt, resulting in the instantaneous precipitation of insoluble calcium alginate, which can then be further processed. Introducing varying proportions of sodium ions during manufacture can produce products having different absorption rates.

Safety Profile

Poison by intravenous route. Moderately toxic by intraperitoneal route. When heated to decomposition it emits acrid smoke and irritating fumes.

Safety

Calcium alginate is widely used in oral and topical formulations, and in foods.
In 1974, the WHO set an estimated acceptable daily intake of calcium alginate of up to 25 mg, as alginic acid, per kilogram bodyweight.
When heated to decomposition, it emits acrid smoke and irritating fumes.
LD₅₀ (rat, IP): 1.41 g/kg
LD₅₀ (rat, IV): 0.06 g/kg

storage

Calcium alginate can be sterilized by autoclaving at 1158℃ for 30 minutes or by dry heat at 1508℃ for 1 hour. Calcium alginate should be stored in airtight containers.

Incompatibilities

Calcium alginate is incompatible with alkalis and alkali salts. Propranolol hydrochloride has been shown to bind to alginate molecules, suggesting that propranolol and calcium ions share common binding sites in the alginate chains; the formation of the calcium alginate gel structure was impeded in the presence of propranolol molecules.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral tablets). Included in nonparenteral medicines licensed in the UK.