Interfacial Amine Engineering Unlocks Enhanced MRI Relaxivity in Silica-Coated Hematite Nanoparticles

Engineering the surface architecture of MRI contrast agents is fundamental to achieving superior contrast efficiency and multifunctional therapeutic capability. We report the silica-coated hematite (SIO) functionalized with amine groups via (3-aminopropyl) trimethoxysilane (APTMS) to assess their effects on MRI relaxivity and redox activity. Upon amination, the transverse relaxivity (r2) increased from 6.20 ± 0.02 to 44.8 ± 0.1 mM-1 s-1 at 1.5 T. Notably, the prepared hematite nanoparticles exhibit exceptionally high relaxivity, among the highest reported for hematite systems. The higher transverse relaxivity shows that they could be excellent T2 MRI contrast agents. In contrast, SIO exhibited enhanced hydroxyl radical generation and greater glutathione (GSH) depletion, indicating superior Fenton-like catalytic activity compared to amine-functionalized silica-coated hematite (SIOA). These results show an important design trade-off: surface coatings make MRI relaxivity and biocompatibility better, but they also make poor ROS-mediated therapeutic potential. This study elucidates the mechanisms by which surface chemistry influences dual imaging and treatment efficacy, offering foundational concepts for the development of multifunctional MRI contrast agents in cancer theranostic.