Comparison of different in vitromucoadhesion testing methods for hydrogels

The purpose of this study was to compare the effects of different in vitromethods and different concentrations of polymers on the mucoadhesive properties of hydrogels. Mucoadhesive gels were prepared with four different polymers: Carbopol971P, Carbopol974P, hydroxypropylmethy cellulose (HPMC K100M) and sodium carboxymethyl cellulose (CMC-Na). The four concentrations of 1%, 1.5%, 2%, and 2.5% were tested. The above formulations were characterized in terms of mucoadhesion with a tensile test, the flowing liquid method and a rheological study. The four polymers all exhibited mucoadhesion according to each of the three methods, and the mucoadhesive properties of the hydrogels increased with increasing concentrations with the exception of Carbopol971P. The rank orders of the hydrogels were not inconsistent across the different testing methods even with the same measurement. Concentrations at the low and high level were found to influence the rank orders of mucoadhesion. The conflicting results confirmed that a stand-alone method or concentration should not be used to evaluate the mucoadhesion of hydrogels.