ABSTRACT
The history of the studies of polysaccharide chitosan dates back to the nineteenth century. However, it is only in the last couple of decades that people have considered chitosan as a kind of biomedical and drug delivery material. Chitosan is a deacetylated form of chitin, which is the second most abundant polymer in nature after cellulose. The slight difference between the chemical structures of chitin and chitosan has, however, resulted in very different consequences in terms of their applications to drug delivery. Chitin is not soluble in water and in most of the common organic solvents used in pharmaceutical industry. Therefore, it is not useful for the development of drug delivery devices. In contrast with chitin, chitosan base can be protonized in acidic solutions and becomes soluble. The positive charges on the chitosan molecule (CM) enable it to interact with polyanions, a process that has been used to obtain micro-and nanoparticulate or nanogel drug delivery systems. In addition to its polycationic characteristics, chitosan has shown some other excellent properties (e.g., nontoxicity, biocompatibility, mucus adhesion, and biodegradation). As a result, chitosan has been used for a variety of drug delivery systems [1,2]. Some of the chitosan-based drug delivery systems are summarized in Table 7.1.
