Nanocomposites and nanomaterials

Hydroxyl radicals scavenging by small oxide nanocrystals with variable valence ions
Pavel Maksimchuk1, Kateryna Hubenko1, Vladyslav Seminko1, Andrey Onishchenko2, Iryna Bespalova1, Vladimir Klochkov1, Svetlana Yefimova1
1 Yu.V. Malyukin Nanostructured Materials Department, Institute for Scintillation Materials NAS of Ukraine, 60 Nauky Ave., Kharkiv-61072, Ukraine. 
E-mail: pavel.maksimchuk@gmail.com
2 Department of Physics, Kharkiv National University of Radio Electronics, 14 Nauky Ave., Kharkiv-61166, Ukraine.

Reactive oxygen species (superoxide anions, hydrogen peroxide and hydroxyl radicals) are biologically active molecules which are formed inside the mitochondria of living cells during cellular respiration. Some of them play indispensable role in the metabolism of the cell. At the same time, an increase of the content of hydroxyl radicals (·OH) which are the strongest oxidants among all reactive oxygen species can trigger the number of pathological processes inside the cell from enhanced lipid peroxidation of cell membranes to DNA damage. 
Hydroxyl radicals are formed at water radiolysis during X-ray or gamma-irradiation of the cell. Extremely high reactivity of ·OH radicals (average ·OH lifetime in the biological environment of only few nanoseconds) makes the task of its effective elimination by the internal systems of the living cell rather difficult. We propose three different types of small oxide nanocrystals with variable valence ions (CeO2, GdYVO4 and TiO2) as promising materials for effective elimination of hydroxyl radicals.
CeO2, GdYVO4 and TiO2 nanocrystals demonstrate high ROS scavenging activity against hydroxyl radicals formed during X-ray irradiation of water solutions. Hydroxyl radicals scavenging properties have been revealed to be directly related to the high content of reduced variable valence ions (Ce3+ for CeO2, V4+ and V3+ for GdYVO4, Ti3+ for TiO2) which could donate electrons in hydroxyl radical neutralization reaction. A large amount of structural defects, such as oxygen vacancies, is a feature of small oxide nanocrystals. Formation of oxygen vacancies can be accompanied by the reduction of neighboring atoms, which were shown by XPS experiment for all types of nanocrystals.
The efficiency of hydroxyl radicals scavenging by small oxide nanocrystals with variable valence ions (CeO2, GdYVO4 and TiO2) in water solutions allows suggesting such materials as effective antioxidants in living cells as well.