Pro-oxidant action of preliminarily UV-activated orthovanadate nanocrystals

The well-known ability of dielectric nanocrystals to generate reactive oxygen species (ROS) under X-ray excitation enhances sufficiently the efficiency of cancer radiotherapy making such nanoparticles a promising material for biological and medical applications. However, the ionizing radiation used during radiotherapy has a great disadvantage of being dangerous not for cancer cells only, but for whole organism as well. For solving this problem, we propose orthovanadate nanocrystals with pro-oxidant activity without any external stimuli after preliminary irradiation of nanoparticles with UV-light [1]. Pro-oxidant action of preliminarily UV-activated orthovanadate nanocrystals is shown to be associated with superoxide and hydroxyl radical generation and depended on the size of nanocrystals and, consequently, on the concentration of surface defects [2]. Oxide nanocrystals contain high amount of structural defects (such as oxygen vacancies) which could serve as traps for charge carriers and are responsible for ROS production in nanocrystals even long time after irradiation. For small 2 nm preliminarily UV-activated GdYVO₄:Eu³⁺ nanocrystals, strong superoxide and hydroxyl radical production has been revealed, whereas for larger preliminarily UV-activated GdVO₄:Eu³⁺ nanocrystals, low level of superoxide and negligible one of hydroxyl radicals production have been detected during the storage of the samples in the darkness. Orthovanadate nanocrystals with «dark» redox activity after preliminarily UV-activation could be prospective for the application in biomedical area as multifunctional therapeutic agents for cancer treatment. (author)