Imani R, Dillert R, Bahnemann BW, Pazoki M, Apih T, Kononenko V, Repar N, Kralj-Iglič V, Boschloo G, Drobne D, Edvinsson T, Iglič A
[ site ] Small, 2017

Materials with controllable multifunctional abilities for optical imaging (OI) and magnetic resonant imaging (MRI) that also can be used in photodynamic therapy are very interesting for future applications. Mesoporous TiO₂ sub-micrometer particles are doped with gadolinium to improve photoluminescence functionality and spin relaxation for MRI, with the added benefit of enhanced generation of reactive oxygen species (ROS). The Gd-doped TiO₂ exhibits red emission at 637 nm that is beneficial for OI and significantly improves MRI relaxation times, with a beneficial decrease in spin–lattice and spin–spin relaxation times. Density functional theory calculations show that Gd³⁺ ions introduce impurity energy levels inside the bandgap of anatase TiO₂, and also create dipoles that are beneficial for charge separation and decreased electron–hole recombination in the doped lattice. The Gd-doped TiO₂ nanobeads (NBs) show enhanced ability for ROS monitored via ^•OH radical photogeneration, in comparison with undoped TiO₂ nanobeads and TiO₂ P25, for Gd-doping up to 10%. Cellular internalization and biocompatibility of TiO₂@xGd NBs are tested in vitro on MG-63 human osteosarcoma cells, showing full biocompatibility. After photoactivation of the particles, anticancer trace by means of ROS photogeneration is observed just after 3 min irradiation.