Viscoelasticity of anionic polymers and their mucociliary transport on the frog palate

The influence of formulation variables on the rheology of polyanionic formulations and the relationships between viscoelastic properties and mucociliary transport rate were investigated. Polymeric samples were oscillated from 0.001 to 5 Hz using either a "cone and plate" or a "coaxial cylinder" measuring system. The mucociliary transport rates of polymeric samples were determined and compared movement of charcoal powder on the frog palate. For the linear polymeric solutions, sodium carboxymethylcellulose and sodium alginate, the elastic modulus (G') increased with increasing amplitudes during frequency scan. However, the G' or viscous modulus (G'') of partially cross-linked polyacrylic acid (cPAA) samples did not change significantly under oscillation. Both G' and G'' of cPAA samples were significantly influenced by the amount of salt present in the formulation. The rheology of 2% (w/w) cPAA in 90:10 (w/w) propylene glycol:alcohol changed from a viscous fluid to a coarse suspension after neutralization. The pH increased gradually when the nonaqueous formulation reacted with water and the maximum dynamic moduli were obtained after incorporating 20% (w/w) water in the formulation. A negative correlation was found between the G' of linear polyanionic samples and the relative transport rate. However, the lowest mucociliary transport rate was observed when the loss tangent (G''/G') was around 0.4-0.5.