In vitro/ex vivo methods for the evaluation of bioadhesive polymers. A preliminary study

Two apparatuses for the evaluation of the bioadhesive properties of pharmaceutical polymers were described and tested. The first apparatus was designed in our laboratory, whilst the second is a commercially-available equipment: Texture Analyser. Both systems are fitted with specific probes for in vitro and ex vivo experiments. Different polymeric samples were tested in the form of tablets, and, as reference substrates, either a flat surface of Plexiglas or a bovine buccal mucosa were used. Bioadhesion was established in standardized conditions, and the force needed to separate the sample from the substrate was recorded as a function of distance. To describe the adhesion properties of the samples, maximum strength and work of adhesion were considered, and the results obtained with the two apparatuses were compared. The data obtained were reproducible, and, from both in vitro and ex vivo experiments, the polymers analyzed show good adhesion properties. Finally, to simulate buccal application, the bioadhesion properties of the same polymers were evaluated ex vivo as a function of contact time and degree of hydration. These two parameters seem to play an important role in the establishment of bioadhesion bonding.