Studies on interfacial phenomena in the field of pharmaceutical sciences

Abstract

Various interfacial phenomena in the field of pharmaceutical sciences were investigated. A striking difference was found in the mode of hemolytic action between anionic and cationic surfactants, mainly due to the difference in membrane components with which these two types of hemolytic agent interact in the surface region of erythrocytes. The permeability of microcapsule membranes composed of electrically neutral polymers toward water-soluble solute increased with increasing microcapsule size while that toward sparingly-soluble solute decreased as the microcapsule size increased. In the case of polyelectrolyte microcapsule membranes, which have many dissociable groups, the permeability was found strongly dependent on the pH of the medium. Degradation of poly(L-lactic acid) microcapsules was revealed to start from the surface through electrophoretic mobility measurements, the rate of which was noticeably affected by the pH and ionic strength of the medium and the presence of plasma proteins. Disintegration of polyelectrolyte microcapsules was caused by the action of such fibrous proteins as fibrinogen principally through hydrophobic interaction between the constituent polymers and the protein. An important role of the complement was found in the adhesion of platelets to the surface of negatively charged microcapsules. Microcapsules with different surface potentials were phagocytosed least by phagocytes when they had a surface potential identical with that of the cells. Cell electrophoresis was applied to estimate the charge distribution in the surface region of biological cells and to elucidate the action mechanism of inhalation anesthetics.