bioadhesive polymers in the form of , or as a coating on , microcapsules containing drugs or bioactive substances which may serve for therapeutic , diagnostic , or diagnostic purposes in diseases of the gastrointestinal tract , are described . the polymeric microspheres all have a bioadhesive force of at least 11 mn / cm 2 . techniques for the fabrication of bioadhesive microspheres , as well as a method for measuring bioadhesive forces between microspheres and selected segments of the gastrointestinal tract in vitro are also described . this quantitative method provides a means to establish a correlation between the chemical nature , the surface morphology and the dimensions of drug - loaded microspheres on one hand and bioadhesive forces on the other , allowing the screening of the most promising materials from a relatively large group of natural and synthetic polymers which , from theoretical consideration , should be used for making bioadhesive microspheres .