Plasma substitutes Polysaccharides

A number of other polysaccharides, such as glycogen, dextran, chitin, etc., possess interesting structures for chemical modification [103,104]. Dextran has been used as a blood plasma substitute. Although it can be converted to films and fibers, chitin s relatively small resource restricts its commercialization. 

In addition to murein, bacterial polysaccharides include dextrans—glucose polymers that are mostly al 6-linked and al 3-branched. In water, dextrans form viscous slimes or gels that are used for chromatographic separation of macromolecules after chemical treatment (see p.78). Dextrans are also used as components of blood plasma substitutes (plasma expanders) and foodstuffs. 

Many pioneer structural investigations were carried out in other groups of polysaccharides, notably on inulin, on the xylan from esparto, on the mannan from yeast and on a series of bacterial polysaccharides amongst the latter were included somatic and lipoid-bound polysaccharides from M. tuberculosis. Noteworthy also was the work on the dextran produced by strains of Leuconostoc, which is showing grqat promise as a blood plasma substitute. 

Numerous other polysaccharides are known, such as gum arabic and other gums and mucilages, chondroitin sulfate (found in cartilage), the blood anticoagulant heparin (found in the liver and heart), and the dextrans (used as blood plasma substitutes). 

Dextran is an important extracellular bacterial polysaccharide widely used as a molecular sieve for purification and separation of biomacromolecules, like proteins, nucleic acids, and polysaccharides, as matrices (e.g., Sephadex ) in size-exclusion chromatography (Naessens et al. 2005). Dextran is also used in clinical research as clinical dextran, a blood plasma substitute, in alleviate iron-deficiency anemia, and in confectionary to improve moisture retention, viscosity, and inhibit sugar crystallization (Sutherland 1997,1998,1999 Kumar et al. 2007 Kumar and Mody 2009). 

Dextran is a nontoxic water-soluble polysaccharide consisting mainly of a-1,6 linked D-glucopyranose residues with a low percentage of a-1,2, a-1,3, and a-l,4-linked side chains (Figure 2.37) [269]. It is mainly used as a blood plasma substitute [270]. The chemical structure of dextran includes a-(l -> 6) linkages that can vary from 97% to 50% of total glucosidic bonds [271, 272]. Dextran has wide applications in novel drug delivery systems as a polymeric carrier. 

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