Exploring the Factors Affecting the Solubility of Chitosan in Water

Abstract

We explore the role of crystallinity and inter‐ or intramolecular forces in chitosan for its solubility in water and demonstrate the expansion of its solubility to a wider pH range. Due to its semicrystalline nature, derived mainly from inter‐ and intramolecular hydrogen bonds, chitosan is water‐soluble only at pH < 6. In acidic conditions, its amino groups can be partially protonated resulting in repulsion between positively charged macrochains, thereby allowing diffusion of water molecules and subsequent solvation of macromolecules. We show that chemical disruption of chitosan crystallinity by partial re‐acetylation or physical disruption caused by the addition of urea and guanidine hydrochloride broadens the pH‐solubility range for this biopolymer.magnified image

Chitosan and its hydrophobic derivatives: Preparation and aggregation in dilute aqueous solutions

“…Thus, as was shown by Anthonsen et al [43,48] for samples obtained by deacetylation, aggregation becomes more intense with the increasing degree of acetylation [43,48]; the same effect was observed by Domard et al for reacetylated samples [39,49]. The second kind of behavior (a more distinct aggregation with a decrease in DA) was like wise described for both deacetylated [54] and reacety lated [50,53] samples.…”

“…In other studies, in contrast, the aggre gation of chitosan is suppressed after incorporation of acetyl groups in polymer chains [50,53,71,105]. This result may be explained by a decrease in the crystallin ity of chitosan due to steric hindrances arising from an increase in the amount of bulky substituents.…”

“…In another series of studies [50,53,54], the reverse effect was observed, namely, well defined aggregation for chitosan free of acetyl groups and the lowest ten [1,50,82]. Figure 2 displays the particle size distributions obtained for chitosan samples (М = 1.1 × 10 5 ) with DA = 0 and 56% via dynamic light scattering.…”

Controlling cell adhesion using layer-by-layer approaches for biomedical applications

“…The use of CHI in its original form is difficult because of its insolubility in water, high viscosity, and tendency to coagulate with proteins at high pH. Thus, functional derivatives of CHI by chemical modifications with increased water solubility are often used [171,172]. LbL films built from CHI and other biopolymers have been explored to leverage on the properties of CHI as a bactericidal agent and negatively charged biopolymers as an anti-adhesive agent.…”

Chitosan molecular structure as a function of N‐acetylation

“…To date, a number of contributing components to chitin and chitosan solubility have been reported, 17,[71][72][73] such as intramolecular hydrogen bonding, hydrophobic interactions and electrostatic forces. To address these issues, six 20-ns simulations of crystal-like nanoparticles (starting from a two-fold helix conformation and packed in anti-parallel fashion setup) were carried out at the same pH and acetylation used for the solvated chains.…”