ABSTRACT
Among the numerous polymers that are actually used, or have
been proposed, for the formulation of conventional and modified
release dosage forms, natural polysaccharides and their derivatives
are indeed the most employed and versatile polymeric materials.
But it must be pointed out that polysaccharides show an even
wider variety of biomedical applications, ranging from their intrinsic
biological activity to their ability in living cell encapsulation, as
well as from bone and cartilage repair to the preparation of
friendly scaffolds for tissue engineering. Furthermore, remaining
within quite close areas of interest, polysaccharides are often
also present in cosmetic and personal care products [70], are
used as food additives [125] and have even been proposed in
formulations for paper and painting cleaning [86]. The peculiar
and diversified properties of polysaccharides can be related to the
different molecular weights and chemical composition that these
macromoleculesmay have, aswell as to the various type and number
of reactive groups that can be present on each single unit. These
properties allow numerous chemical modifications that can be
appropriately tailored according to the specific use that is assigned
to thesemacromolecules. Polysaccharides are usually abundant (it is
well known that cellulose is the most abundant organic compound
on earth) and available from various renewable natural sources such
as animals (e.g., chitin/chitosan, chondroitin), plants (e.g., pectin,
guar gum), algae (e.g., alginates, agar, carrageenans), microbes, and
fungi (e.g., dextran, xanthan gum, gellan, scleroglucan). Finally, but
not less important, polysaccharides are, with only a few exceptions
[103, 112], biocompatible and nontoxic products and can be
classified as GRAS (generally recognized as safe).
