Citric-Acid-Modified\nIron–Titanium Dioxide\nNanodots for Fenton Reaction-Driven MRI Contrast Enhancement of In\nVivo Hydrogen Peroxide

Reactive oxygen species (ROS), including hydroxyl and\nsuperoxide\nradicals, play crucial roles in disease development and are recognized\nas indicators for cancer and inflammation. Although these radicals\npossess paramagnetism due to unpaired electrons, their high reactivity\nand low in vivo concentrations challenge MRI detectability. In this\nstudy, we utilized iron–titanium dioxide nanodots modified\nby citric acid (Fe-TiO<sub>2</sub>-CA) as catalysts in the Fenton\nreaction to efficiently convert hydrogen peroxide, a diamagnetic molecule,\ninto paramagnetic hydroxyl radicals. This conversion maintained the\nconcentration of hydroxyl radicals within the detectable range for\nMRI. Our results demonstrated that Fe-TiO<sub>2</sub>-CA significantly\nshortened the T1 relaxation time in H<sub>2</sub>O<sub>2</sub> solutions.\nImportantly, this approach successfully enabled in vivo imaging of\nareas with elevated hydrogen peroxide concentrations typical of cancerous\nand inflamed tissues. These findings highlight the potential of Fenton\nreaction catalysts as innovative diagnostic tools for MRI-based detection\nof diseases with elevated hydrogen peroxide levels.