Korean scientists obtained nanoparticles of cerium dioxide with a surface layer of mixed oxide of manganese, which provides enhanced catalytic activity against reactive oxygen particles — one of the indirect mechanisms of influence of radiation on living organisms. The resulting nanoparticles are biocompatible and have increased the survival of mice after high doses of radiation to 67 percent. Article published in the journal Advanced Materials.
One of the effects of radiation on living organisms — radiolysis of water, during which the formation of reactive oxygen particles (for example, O2-, H2O2 and OH radicals.). These particles can oxidize organic molecules, destroying living tissue. With a sharp dose of irradiation in excess of six gray, most cases ended in the death of a patient for three weeks. Existing anti-radiation drugs, such as amifostine, quickly removed from the body and to a small extent able to contain the oxygen particles, which is necessary to use high doses have negative side effects. But because scientists are trying to find a new non-toxic drugs long-term, high antioxidant capacity.
In recent years, scientists have paid close attention to inorganic nanomaterials with antioxidant properties — oxides of cerium, manganese and vanadium. They are already well-proven in use against reactive oxygen particles, e.g., nanoparticles Mn3O4 have coped with inflammation in the mouse ear. This catalytic ability is due to a slight transition between the stable oxidation States of transition metals. In order to increase the catalytic ability of antioxidants, the researchers introduce additional ligands or increase mechanical stresses on the surface. The latter approach significantly improves the catalytic properties of metal nanoparticles with architecture of the core-shell.
A group of Korean scientists from Seoul National University under the guidance of Chuni Park (Kyungpyo Park) and Tahuna Hyun (Taeghwan Hyeon) has obtained nanoparticles of cerium oxide with a surface layer of mixed oxide manganese (II, III) and used them to protect tissues of the mouse from radiation exposure. Such particles saved the life of 67 percent of the mice exposed to radiation with a dose of 13 gray.
For producing nanoparticles, researchers have used seed crystals of cerium dioxide. They were immersed in a solution of manganese chloride on the surface began, the reaction of oxidative substitution. Cerium was partially restored to the oxidation state +3, and manganese were oxidized to +3, which led to the formation of a layer of manganese oxide on the surface of the nanocrystals. To use such particles in the body, scientists were coated with phospholipid polyethylene glycol.