Polysaccharide systems, structuring alginate

Alginate-poly(L-lysine) and alginate-chitosan are, by far, the most common polymer-polymer coacer-vation systems, with the former often pregelled, in bead form, with divalent cations such as calcium or barium. As Table 2 indicates, polysaccharides with a rigid structure are generally favored for polysalt formation. 

The drive towards microencapsulation systems based on the use of synthetic hydrophilic methacrylate based polymers is fueled by their proven biocompatibility, (56) hydrolytic stability, (57) ease of synthesis (66, 67) and enormous structural diversity made possible through copolymerization. In contrast, interest in polysaccharide gel formers such as alginate is founded upon the relative ease of capsule formation under physiological conditions. It would seem inevitable that attempts be made to combine the host biocompatibility and stability of methacrylate based polymers with the ease of capsule formation... 

A number of factors must be considered when selecting a suitable polysaccharide or combination of polysaccharides to fabricate a biopolymer-based delivery system. It is important to establish suitable environmental and solution conditions in which the polysaccharide molecules can associate with other polysaccharide or non-polysaccharide structure-forming molecules. To do so, one needs to know the physicochemical properties of the polysaccharides involved, such as helix-coil transition temperatures (for carrageenan, alginate,pectin) electrical properties (pKa values) sensitivity to specific monovalent or multivalent ions or susceptibility to enzyme or chemical reactions (BeMiller and Whistler, 1996). The most widely used carbohydrates for encapsulation purposes are probably alginates (Kailasapathy and Champagne, 2011 Kainmani et al, 2011), starch (Li et al, 2009) and its linear biopolymer amylose (Lalush et al, 2005). 

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