2.7. Ex-Vivo Mucoadhesion Strength Measurement

The ex-vivo mucoadhesive strength evaluation of prepared films was performed by the modified two-armed physical balance method [46]. Porcine buccal mucosa excised from just slaughtered pigs was used as model tissue and handled without any pre-treatment. A tissue portion of the inner part of the cheek was glued by cyanoacrylate resin (Super Attak Loctite^®, Henkel Italia Srl, Milan, Italy) on a glass support (Petri dish) and placed in a thermostatic bath at 37 ± 1°C. The film’s disk was fixed using a bi-adhesive to the lower side of a rubber stopper hanging from the balance arm. Before starting the measurements, the mucosal tissue was wetted with 50 µL of simulated salivary fluid and then the film was placed on the tissues so it just touched the mucosal surface and a light force with a fingertip was applied for 20 s. A temperature of 37 ± 1 °C was maintained throughout the experiment. The measurements started 5, 10, and 15 min after application, thus allowing for different time contacts. 0.8 cm diameter disks, taken from 3 different films, were used to perform the test.

The grams required to detach the film from the mucosal surface provided the measurement of mucoadhesive strength, according to the equation:

Then, detachment force was calculated as:

The maximum adhesive force was determined as the average of 3 measurements (n = 3) [39].