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 HCl (pH 1) or 0.1 N acetate buffer (pH 5.5) were measured with a Brookfield viscometer in the absence (eta m) or presence (eta t) of selected neutral, anionic, and cationic polymers (0.1-2.5%, w/v). Viscosity components of bioadhesion (eta b) were calculated from the equation, eta t = eta m + eta p + eta b, where eta 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 = eta b sigma, where sigma is the rate of shear/sec. eta b's and F's for polyelectrolytes, e.g., polyacrylic acid, cationic gelatin, and chitosan were always higher in acetate buffer than in HCl. Validity of the technique and the effect of ionic charge, polymer conformation, and rate of shear on eta b and F are discussed, as is a comparison of this method to other methods for evaluating bioadhesive materials.