Mucoadhesive behaviour of emulsions containing polymeric emulsifier

Over the last two decades the attention has been focused on mucoadhesive dosage forms as a possibility to improve the residence time on a specified region of the body. In addition to bioadhesivity, controlled drug release from the dosage form is also desirable. Pemulen TR1 and Pemulen TR2 are cross-linked block copolymers of poly(acrylic acid) and hydrophobic long-chain methacrylates. They are able to stabilize o/w emulsions because their short lipophilic part integrates into the oil droplets whilst their long hydrophilic part forms a micro-gel around the droplet. In this study, correlations between the microstructure of these emulsions and the bioadhesive behaviour were found. Rheological and thermogravimetric methods were used to examine the microstructure of the emulsions. The mucoadhesive measurements were performed by tensile test and the bioadhesive bond between the polymer emulsifier and mucin was visualized by confocal laser scanning microscopy. It was established that (i) these emulsion form a special structure, which depends on the components, (ii) there were no remarkable changes in bioadhesive force and work when the oil content was increased in the emulsions, and (iii) the emulsions in which the polymeric emulsifier formed a special structure showed stronger adhesivity than the ones with simple polymer network.