Mucoadhesive interactions between synthetic polyaspartamides and porcine gastric mucin on the colloid size scale.

Synthetic polyaspartamides with various functional side groups including primary, secondary, tertiary amine or carboxyl groups were designed to explore the effect of chemical composition on polymer-mucin interactions. Since the molecular weight of the polymers and the degree of modification were identical for each derivative, the role of the functional groups could be evaluated. Chitosan was used as a control sample due to its strong interaction with mucin primarily through electrostatic forces. Mucoadhesive interactions of the polymers with the aqueous dispersion of commercially available porcine gastric mucin were probed on the colloid size scale using various methods including turbidimetric titration, dynamic light scattering and zeta potential measurements. Both the charge of the polymers and the type of amine groups had a pronounced effect on the interactions. The interactions were further analysed by partially screening them with either sodium chloride or urea. The results obtained allow us to classify these polymers in terms of in vitro mucoadhesive strength, which can be useful in the design of mucoadhesive formulations.