Radiocatalytic performance of oxide-based nanoparticles for targeted therapy and water remediation

The role of energy deposition on the luminescence sensitization in porphyrin-functionalized SiO2/ZnO nanoparticles under X-ray excitation

Hybrid nanoscintillators, which feature a heavy inorganic nanoparticle conjugated with an organic emitter, represent a promising avenue for advancements in diverse fields, including high-energy physics, homeland security, and biomedicine. Many research studies have shown the suitability of hybrid nanoscintillators for radiation oncology, showing potential to improve therapeutic results compared to traditional protocols. In this work, we studied SiO2/ZnO nanoparticles functionalized with porphyrin as a photosensitizer, capable of producing cancer cytotoxic reactive oxygen species for possible use in radio-oncological therapeutics. Radioluminescence measurements under increasing energy of the ionizing radiation beam up to 10 keV show sensitization of porphyrin moieties on SiO2/ZnO. This can be attributed to an increase in energy deposition promoted by the ZnO nanoparticles, which have a higher density and atomic number. This assumption was confirmed by computational simulations of energy deposition after the first interaction of ionizing radiation with SiO2, ZnO, and air. Indeed, Monte Carlo simulations evidence that, despite a decrease in the absolute number of X-rays interacting within the system while increasing the energy of the beam, at 10 keV, the presence of ZnO is dominant to enhance energy deposition. Hence, these experimental and computational studies evidence the importance of each hybrid nanosystem component in the scintillation process. This work shows how an appropriate choice of constituents, in terms of physicochemical properties and architecture, can favour energy deposition mechanisms under X-ray irradiation and thus can boost the hybrid nanosystems' performance for diverse biomedical scintillation-based applications.

Oxidative stress-modifying effects of TiO2nanoparticles with varying content of Ti3+(Ti2+) ions

Nanoparticles (NPs) with reactive oxygen species (ROS)-regulating ability have recently attracted great attention as promising agents for nanomedicine. In the present study, we have analyzed the effects of TiO2defect structure related to the presence of stoichiometric (Ti4+) and non-stoichiometric (Ti3+and Ti2+) titanium ions in the crystal lattice and TiO2NPs aggregation ability on H2O2- and tert-butyl hydroperoxide (tBOOH)-induced ROS production in L929 cells. Synthesized TiO2-A, TiO2-B, and TiO2-C NPs with varying Ti3+(Ti2+) content were characterized by x-ray powder diffraction, transmission electron microscopy, small-angle x-ray scattering, x-ray photoelectron spectroscopy, and optical spectroscopy methods. Given the role of ROS-mediated toxicity for metal oxide NPs, L929 cell viability and changes in the intracellular ROS levels in H2O2- and tBOOH-treated L929 cells incubated with TiO2NPs have been evaluated. Our research shows that both the amount of non-stoichiometric Ti3+and Ti2+ions in the crystal lattice of TiO2NPs and NPs aggregative behavior affect their catalytic activity, in particular, H2O2decomposition and, consequently, the efficiency of aggravating H2O2- and tBOOH-induced oxidative damage to L929 cells. TiO2-A NPs reveal the strongest H2O2decomposition activity aligning with their less pronounced additional effects on H2O2-treated L929 cells due to the highest amount of Ti3+(Ti2+) ions. TiO2-C NPs with smaller amounts of Ti3+ions and a tendency to aggregate in water solutions show lower antioxidant activity and, consequently, some elevation of the level of ROS in H2O2/tBOOH-treated L929 cells. Our findings suggest that synthesized TiO2NPs capable of enhancing ROS generation at concentrations non-toxic for normal cells, which should be further investigated to assess their possible application in nanomedicine as ROS-regulating pharmaceutical agents.