Polysaccharides as Nanomaterials for Therapeutics - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 127

5.2.4 Dextran
Dextran is a high-Mw branched polysaccharide composed of α-(1,6)-
linked glucan with side chains attached to the three positions of
the backbone glucose units (Figure 5.1). Dextran is obtained from
bacterial cultures of the lactic-acid bacteria such as Leuconostoc
mesenteroides NRRL B-512 [4]. Dextran is water soluble and is also
soluble in a wide range of solvents, among them methyl sulphoxide,
ethylene glycol, glycerol, and 4-methylmorpholine-4-oxide. Low-Mw
dextran and not the native dextran is usually used for both clinical
purposes (mainly due to its antithrombotic eff ect) and nanoparticle
preparation. Low-Mw dextran is usually achieved by acid hydrolysis
of the native dextran [35]. The polyanion dextran sulfate is derivate
of dextran, which contains approximately two to three sulfate
groups per glucosyl residue [36]. Dextran sulfate is a biodegradable
polymer that has been widely used in pharmaceutical applications
[36]. However, dextran sulfate is not completely inert material. It
has inhibitory and stimulatory eff ects on several enzymes [37], and
it possesses the ability to stimulate B-cell proliferation [38] and to
increase permeability of lymphocytes [39].
5.2.5 Cyclodextrins
Cyclodextrins are cyclic oligomers of α-(1,4) linked-glucopyranosyl
that are produced from starch by enzymatic conversion (Figure 5.1).
There are three main members of the cyclodextrin family, composed
of six, seven, and eight glucose units and known as α-, β-, and
γ-CD, respectively. Cyclodextrins have a hydrophilic exterior and a
hydrophobic cavity that enables them to act as hosts to hydrophobic
molecules [40]. This ability to form inclusion complexes has been
widely studied since its discovery. It is utilized in many industrial
products, analytical methods, and technologies [41], including the
production of cyclodextrin-based nanoparticles [42]. Cyclodextrins
are biocompatible, do not elicit immune responses, and have low
toxicities in animals and humans [43]. Therefore, they are used in
pharmaceutical applications for numerous purposes, including
improving the bioavailability of drugs [43]. Cyclodextrin-based
therapeutics have been reviewed elsewhere [43].