Association under shear flow in aqueous solutions of pectin

In vitro measurements of mucoadhesive properties of six types of pectin

The objective of this study was to measure and compare the specific- and general mucin interaction of six pectin types from three manufacturers, differing mainly in the degree of methoxylation and degree of amidation. Mucoadhesive properties were measured using a texture analyzer. It was found that an intermediate degree of methoxylation (35 and 36%) improved the specific mucin interaction. Amidation did not increase mucin interaction. Samples from different manufacturers did not alter these conclusions. This study indicates that the general classification of pectin as a poor mucoadhesive, without differentiating between the amount and type of substituents, probably is an oversimplification.

Altering Associations in Aqueous Solutions of a Hydrophobically Modified Alginate in the Presence of β-Cyclodextrin Monomers

The formation of associative networks in semidilute aqueous solutions of hydrophobically modified alginate (HM-alginate) is dependent on intermolecular hydrophobic interactions. Addition of beta-cyclodextrin (beta-CD) monomers to the system provides decoupling of these associations via inclusion complex formation with the polymer hydrophobic tails. This results in a dramatic decrease in the viscoelastic response of the system and a more extended local structure of the polymer chains, as shown by small-angle neutron scattering (SANS) measurements. The zero-shear viscosity decreases about an order of magnitude when the beta-CD concentration is increased from 0 to 12 mm. The lifetime of the associative network decreases strongly with increasing levels of beta-CD addition. These findings clearly demonstrate that the hydrophobic association effect is efficiently reduced as the amount of beta-CD is increased. In the framework of drug delivery, this effect may be useful to improve the release of therapeutic molecules that can be entrapped in the polymer matrix.