| CAS No.: | 9005-38-3 |
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| Color: | White |
| Appearance: | Powder |
| Quality: | High |
| Transport Package: | Paper |
| Specification: | large |
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Audited Supplier For decades, alginates have been used as devices in various human health applications: in drug delivery systems (DDSs), traditional wound dressings, as a dental impression material, and in some formulations preventing gastric reflux. For a summary of the use of alginates in oral DDS, please see Reference 42. In DDS, the main advantage of alginates is their property of preserving a solid-like attribute (gel) under two different conditions (cross-linked with ions and the alginic acid gel). Delicate compounds may hence be protected against the acid influence of gastric juice, both by preventing convection flow and by acting as a buffering agent in the stomach. Oral administration of colon-targeted drugs based on alginates as excipient has been successfully obtained in tablets containing viable lactic acid bacteria43 and colon-specific delivery of bee venom peptide by applying alginate gel beads containing liposomes.44
Alginate/chitosan microcapsules have also been studied as possible systems for controlled delayed release of orally administered drugs. Positive results have been reported, for example, for acid-labile water-soluble mistletoe lectins for potential cancer therapy45 and for controlled release of HCl.46 DDS for controlled release of drugs for the treatment of systemic hypertension in order to obtain a reduced administration frequency is another important area. Here, alginates have been used as an excipient for verapamil.47,48
As dental impression material (e.g., Jeltrate), alginates have been used for several decades.49 It is based on a dry mix of alginate and gelling agents, which will set within minutes upon the addition of water. These materials have also been suggested for use as a device for such diverse applications as taking impressions of the nose prior to rhinoplasty,50 as molds for measuring wound volumes,51 and as molds for the manufacture of polycarbonate face masks for the treatment of hypertrophic scars.52
Alginate-based raft-forming formulations have for 40 years been used in the treatment of heartburn and gastric reflux.53 The most famous antireflux brand is Gaviscon, where alginate is administered in a soluble form. Upon contact with the gastric content, it will build a physical raft on top of the stomach preventing gastric reflux into the esophagus, providing symptom relief within minutes.54 These formulations are considered reasonably safe with little or no adverse effects, as they are also prescribed to infants55 and against heartburn during pregnancy.56
In dressings for the management of dermal wounds, alginates have been used successfully for decades (e.g., Sorbsan, Seasorb, and Kaltostat). Applying Ca-alginate dressings appears to be an appropriate topical treatment of diabetic foot lesions with respect to both healing and tolerance,57 and Ca-alginate dressings can preferably also be used in postsurgical wounds being allowed to heal by second intention.58 It has been pointed out that Ca2+ ions, playing an important role in the normal homeostasis of mammalian skin by serving as a modulator in keratinocyte proliferation and differentiation, could be released from Ca-alginate fibers promoting early-stage wound healing.59 Some studies have been undertaken to study such dressings to try to distinguish between effects of alginates and the effects of endotoxins on immunological responses.60,61 Most wound dressings made from natural biomaterials will contain endotoxins, which in substantial amounts will give cytotoxic effects on proliferation of fibroblasts, but immunological effects from the alginate itself seem to be present in some products. But it is doubtful if the classical alginate wound dressings contain immunologically active alginate in reasonable quantities (not readily available as of yet). In the future, new and improved alginate wound dressings will probably be seen.62,63
Ca-alginate spheres have become the most widely immobilization vehicle of living cells.25 Carried out in a single-step process under very mild conditions, this method is compatible with most cells. A cell suspension is mixed with a Na-alginate solution and the mixture dripped into a gelling bath containing multivalent cations (usually Ca2+). Each single droplet instantaneously forms a gel sphere entrapping the cells in a three-dimensional lattice. There are numerous possible uses for such systems in industry, medicine, and agriculture, ranging from production of ethanol by yeast, monoclonal antibodies by hybridoma cells to mass production of artificial seed by entrapment of plant embryos.25
Immobilized cells for transplantation purposes represent a very exciting and prosperous application. The main purpose of the gel is to act as a barrier between the transplant and the immune system of the host. Multiple cell types have been suggested for this type of therapy, including parathyroid cells for treating of hypocalcemia and dopamine producing adrenal chromaffin cells for the treatment of Parkinson's disease.64 Most interest has been focused around insulin-producing cells for the treatment of Type I diabetes. Alginate/poly-l-lysine capsules containing pancreatic Langerhans islets have been shown to reverse diabetes in large animals and have also been clinically tested in humans.65 Table 2 lists some potential biomedical application of alginate-encapsulated cells. Ultrapure alginate qualities, being low in pyrogens and easily sterile filtered, are now commercially available for this purpose.
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