Preparation and in-vitro cytotoxicity evaluation of ruthenium polypyridyl-sensitized paramagnetic titania nanoparticles for photodynamic therapy -

Abstract

Core-shell-shell magnetite-silica-titania nanoparticles (Fe3O4@SiO2@TiO2 NPs) were synthesized by successive sol-gel methods. The magnetite cores were electrostatically stabilized and dispersed by the addition of polyacrylic acid. Infrared, energy-dispersive X-ray and X-Ray diffraction measurements of the multilayered NPs confirmed the presence of the surfactant polymer and the three oxides. The surface area, measured by nitrogen adsorption, increased following every step of the synthesis from 95 m2-g to 233 m2-g. The intensity-weighted mean diameter of the TiO2 coated sample was measured by dynamic light scattering and found to be 98.8 nm. Following hydrothermal treatment of the final nanocomposites, a ruthenium polypyridyl dye was anchored to their surface. The total reactive oxygen species (ROS) generation and singlet oxygen production by the obtained hybrid NPs (naked NPs + Ru-dye) were evaluated by fluorescence and UV-Vis spectroscopy in solution. Using a green light (532 nm) for excitation, the total ROS generated by the hybrid NPs were more than 500percent times than those generated by the naked ones, and 550percent more than those generated by the ruthenium dye alone. Employing a white light produced similar results. As for singlet oxygen generation, the hybrid NPs produced negligible amounts. These findings demonstrate that our hybrid NPs can potentially act as type I photodynamic therapy (PDT) agents generating free radicals, unlike the currently employed ones in medicine which follow type II mechanism predominantly (generating singlet oxygen). This type of photosensitizers can prove advantageous in fighting PDT-resilient hypoxic tumors, and avoiding type II photosensitizers-induced hypoxia in non-hypoxic tumor cells.