Crustaceous shells

This chapter describes the main properties and methods for the characterization of polyelectrolytes derived from the biomass. The most important sources are plants, with cellulose and starch, which turn to polyelectrolytes after chemical modifications. CarboxymethylceUulose is the main cellulose derivative used in many industrial applications as good thickener and hydrophilic polymer for aqueous media. Cationic starches are mainly used in the paper industry for fiUa- retention or paper wet-strength. Natural polyelectrol5des are produced by algae with anionic alginates and carrageenans as the major representatives, which are used in food applications and for biomedical devices. In this respect, alginates are often associated in an electrostatic complex with a pseudo-natural polyelectrolyte (chitosan), a cationic polymer extracted from crustaceous shells. 

Chitin, a linear polysaccharide of P-(1 4)-2-deoxy-2-acetamido-D-glucopyranose, is a major polysaccharide found in crustaceous shells and in cell walls of fungi. In its chemical structure, chitin is similar to cellulose, but it is different in that it has an acetamide group instead of a hydroxyl group... 

The most commonly used biopol)rmers in drug delivery are shown in Figure 19.2. Chitosan, biopolymer from crustaceous skin or shells, is the most studied for this application reported in 36% of the publications, followed by dextran (17%), alginate (14%) and gelatin (12%). 

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