Poly derivatives chitins, chitosans

Biodegradable polymers can be classified into three categories according to their origin (i) synthetic polymers, particularly aUphatic polyesters, such as poly (L-lactide) (PLA) [1-3], poly(e-caprolactone) (PCL) [4—6], poly(p-dioxanone) (PPDO) [7-9], and poly(butylene succinate) (PBS) [10-12] (ii) polyesters produced by microorganisms, which mainly correspond to different poly(hydroxyalkanoate)s (e.g., poly(P-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) and (iii) polymers derived from natural resources (e.g., starch, cellulose, chitin, chitosan, lignin, and proteins). 

Zhou and coworkers recently reported the synthesis of chitosan-based nanogels and their pH-responsive biomedical applications [123]. Nanogels have been prepared from chitosan and poly(methacrylic acid) (PMAA) polymers in two ways using covalent crosslinking or physical association between the polymers (Fig. 22). Naturally occurring chitin, chitosan, and their derivatives have found widespread applications in various biological settings [124]. 

A contrasting picture is seen for chitosans. Chitosans—as considered in detail in the following Chapter—are derivatives of chitin (after an alkali extraction procedure) and are available in large quantities from the shells of crabs, lobsters and other crustaceans. Pure chitin is poly-N-acetylglucoasmine. The N-acetyl groups are de-acetylated in chitosan to an extent represented by ei-... 

Chitosan is a naturally occurring polymer derived from the shells of crustaceans. It is a derivative of chitin (poly-/V-acetylglucosamine), which is the second most abundant biopolymer after cellulose (Dai et al., 2011). 

Chitin, a poly(saccharide) closely related to cellulose and shown in Figure 4, is being studied by many research groups for a wide variety of biomedical, agricultural and cosmetic applications. Chitin is found mainly in insect and crustacean shells. Most current research centers on the deacetylated chitin, which is called chitosan. Figure 5. Chitosan is now finding some new uses in the textile industry, waste water treatment and medicine.While neither material is likely to be made synthetically on a commercial scale, both polymers are derived from formerly useless... 

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