Hydrogels for buccal drug delivery: properties relevant for muco-adhesion.

In order to develop a muco-adhesive hydrogel for buccal drug delivery it is necessary to understand fully the properties determining adhesiveness as well as mechanisms involved. In this study we measured glass transition temperatures, water contact angles and the peel- and shear detachment forces from porcine oral mucosa, of acrylic acid and butyl acrylate copolymers. The contact angle maximizes at 50% butyl acrylate content. The glass transition temperature decreases from 0% to 100% butyl acrylate. There seems to exist a certain combination of contact angle and glass transition temperature which is related to adhesiveness. This strongly suggests that, in order to obtain a muco-adhesive hydrogel, at least two properties have to be optimized: (1) the polarity of the polymer surface and (2) the molecular mobility of the polymer groups.