A Simple Rheological Method for the in Vitro Assessment of Mucin-Polymer Bioadhesive Bond Strength

A simple viscometric method was used to quantify mucin-polymer bioadhesive bond strength. Viscosities of 15% (w/v) porcine gastric mucin dispersions in 0.1 N HC1 (pH 1) or 0.1 N acetate buffer (pH 5.5) were measured with a Brookfield viscometer in the absence (η_m) or presence (η_t) of selected neutral, anionic, and cationic polymers (0.1–2.5%, w/v). Viscosity components of bioadhesion (1%) were calculated from the equation, η_t = η_m + η_p + η_b, where η_p is the viscosity of corresponding pure polymer solution as measured by an Ostwald viscometer. The forces of bioadhesion (F) were calculated from the equation, F = η_bσ, where σ is the rate of shear/sec. η_b's and F's for polyelectrolytes, e.g., polyacrylic acid, cationic gelatin, and chitosan were always higher in acetate buffer than in HC1. Validity of the technique and the effect of ionic charge, polymer conformation, and rate of shear on η_b and F are discussed, as is a comparison of this method to other methods for evaluating bioadhesive materials.