Polysaccharides as Nanomaterials for Therapeutics - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 124

inflammation, and infections [1, 2]. The growing interest in
nanoparticles derives from the outstanding advantages they off er,
which include protection of the drug from premature degradation,
lower therapeutic toxicity, ability to deliver poorly-water-soluble
drugs, controlled drug release mechanisms, and improved
intracellular penetration [2].
The size and surface characteristics of a nanoparticle are crucial
for the control of its biodistribution in vivo . The small size, which
enables nanoparticles to pass through the smallest capillaries also
promotes passive tumor targeting due to the enhanced permeability
and retention (EPR) eff ect of the tumor vasculature. The passive
targeting is achieved by extravasation of nanoparticles through
increased permeability of the tumor vasculature and ineff ective
lymphatic drainage [2]. In addition, it has been shown that a
combination of nanometric size and hydrophilic surface delays
particle uptake by the mononuclear phagocyte system (MPS) and
therefore promotes long circulation [3].
As the requirements from the nanoparticle are becoming
clear, so are the requirements from the materials used for their
preparation. These materials should be biocompatible and preferably
biodegradable, well characterized, and easily functionalized [2].
Polysaccharides successfully fulfill all of these requirements and are
therefore widely used for the preparation of nanoparticles for drug
delivery.
5.2 Polysaccharides
Polysaccharides are polymers of monosaccharides joined by glycosidic
bonds. These highly abundant molecules are from various origins,
including algal origin (e.g., alginate and carrageenan), plant origin
(e.g., cellulose, pectin and guar gum), microbial origin (e.g., dextran
and xanthan gum), and animal origin (e.g., chitosan, hyaluronan,
chondroitin and heparin) [4]. Naturally occurring polysaccharides
are diverse in their physiochemical properties; there are multiple
chemical structures (Figure 5.1), the chemical composition greatly
varies and so do the molecular weight (Mw) and ionic nature. This
versatility also contributes to a wide range of biological activities.
From a pharmaceutical standpoint, polysaccharides possess many
favorable characteristics such as lack of toxicity, good biocompatibility,