• Microcapsules—pH sensitive, drug release;
  • Drug release—pH sensitive microcapsules, polymerization;
  • Polymerization—pH sensitive microcapsules for drug release;
  • Dosage forms—pH-sensitive microcapsules for drug release


Microcapsules were designed for a sustained drug release, where the external medium controls the rate of release of the drug. As a model, secretin was encapsulated in acryloyl chloride-lysine capsules, and the conditions of formation are described. The scanning electron micrographs show the formation of good spherical microcapsules in the size range of 5–10 μm. The release of secretin was studied in four media having different pH. Polymer dissolution was pH sensitive, and the capsules placed in different media eroded at a constant rate, depending on the pH of the medium. Dissolution of the microcapsules was limited to the polymer buffer media and the drug was released by zero-order kinetics. The possible use of such a system is in the treatment of duodenal ulcers and the diagnosis of pancreatic diseases.