Performance of an in vitro mucoadhesion testing method for vaginal semisolids: Influence of different testing conditions and instrumental parameters

The purpose of this work was to develop an in vitro mucoadhesion testing method for vaginal semisolid formulations. The proposed method was based on the measurement of the force (detachment force, Fdt) and the work (work of adhesion, Wad) needed to detach a sample of cow vaginal mucosa from a semisolid formulation, using a commercially available texture analyzer. Several testing conditions and instrumental parameters were tested in order to evaluate the mucoadhesive potential of a model vaginal semisolid formulation (1% Carbopol® 974P gel). Also, mucoadhesive potential of several commercially available vaginal semisolid products was evaluated. Obtained results showed that the method is reproducible even when the same cow mucosa sample is used up to six times. The similarity of the fluid used to bathe the vaginal mucosa to the one naturally occurring in the vagina influenced considerably the performance of the test, advising that simulation of vaginal fluid properties is important when measuring mucoadhesive properties. Also, temperature of experiment was an important fact to be considered, as results showed slight but significant differences between body (37 °C) and room (20 °C) temperature. Fdt and Wad increased with increasing instrumental parameters while a plateau region was observable at higher values of probe speed, probe force, and mucosa/sample contact time. Comparison between results for Fdt and Wad demonstrated that although both parameters are generally in agreement, Wad seems to be more reliable and reproducible when evaluating mucoadhesion. Evaluation of commercially available formulations confirmed that experimental conditions are important features that can influence significantly the determination of mucoadhesive potential, being the proposed method an interesting and useful tool in the in vitro evaluation of vaginal semisolids.