Why is Chitosan Mucoadhesive?

Abstract

Chitosan is a biocompatible and biodegradable amino polysaccharide, which is soluble in aqueous solutions at pH < 6.5. It has been widely used for developing drug delivery systems because of its excellent mucoadhesive properties. Although many studies report on chitosan being mucoadhesive, the nature of interactions between chitosan and mucin remains poorly defined. Here, we have examined the role of primary amino groups and the role of electrostatic attraction, hydrogen bonding, and hydrophobic effects on aggregation of gastric mucin in the presence of chitosan. Reducing the number of amino groups through their half acetylation results in expansion of chitosan's pH-solubility window up to pH 7.4 but also reduces its capacity to aggregate mucin. We demonstrated that electrostatic attraction forces between chitosan and gastric mucin can be suppressed in the presence of 0.2 mol/L sodium chloride; however, this does not prevent the aggregation of mucin particles in the presence of this biopolymer. The presence of 8 mol/L urea or 10% v/v ethanol in solutions also affects mucin aggregation in the presence of chitosan, demonstrating the role of hydrogen bonding and hydrophobic effects, respectively, in mucoadhesion.

Biophysical Analysis of the Molecular Interactions between Polysaccharides and Mucin

“…3a) as previously described for both commercial and non-commercial preparations. 44,45 Mucin displays a negative -potential at neutral pH which declines as the environment becomes more acidic, and the size of the molecule increases until it reaches a peak at the neutrality point (pH ~2) as shown by the longer relaxation time in Figure 3b. At lower pH values there is a decrease in size, attributed to the contraction of the interchain complexes stabilized by protonated residues.…”

“…16,44 The soluble fraction of partially purified porcine gastric mucin conserves the main structural properties of the molecule required for pH-dependent conformational changes and interactions with polysaccharides ( Fig. 3a) as previously described for both commercial and non-commercial preparations.…”

Fabrication of a tunable glucose biosensor based on zinc oxide/chitosan-graft-poly(vinyl alcohol) core-shell nanocomposite

“…Chitosan (CHIT) is a high molecular weight cationic polysaccharide with potential applications in food, agriculture, cosmetics, pharmaceuticals and biosensor industries [1][2][3][4]. Typically; CHIT is an inexpensive, biocompatible, biodegradable, nonconducting, electroactive biopolymer.…”

Preparation oral levofloxacin colon-specific microspheres delivery: in vitro and in vivo studies

“…Chitosan exhibits several favorable biologic properties that make it an interesting polymer for use in pharmaceutical formulations, as demonstrated by the number of scientific reports published. It is a mucoadhesive and biodegradable polymer that possesses penetration enhancing properties and an adequate toxicity profile (Dodane et al, 1999;Sogias et al, 2008). It is popularly used as colon-specific drug delivery vehicle for colon site infections.…”